CN113132093B - Quantum key distribution method and node - Google Patents

Quantum key distribution method and node Download PDF

Info

Publication number
CN113132093B
CN113132093B CN201911419496.5A CN201911419496A CN113132093B CN 113132093 B CN113132093 B CN 113132093B CN 201911419496 A CN201911419496 A CN 201911419496A CN 113132093 B CN113132093 B CN 113132093B
Authority
CN
China
Prior art keywords
photon
comparison data
position information
node
photons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201911419496.5A
Other languages
Chinese (zh)
Other versions
CN113132093A (en
Inventor
许建平
唐世彪
修亮
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Quantumctek Co Ltd
Original Assignee
Quantumctek Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Quantumctek Co Ltd filed Critical Quantumctek Co Ltd
Priority to CN201911419496.5A priority Critical patent/CN113132093B/en
Publication of CN113132093A publication Critical patent/CN113132093A/en
Application granted granted Critical
Publication of CN113132093B publication Critical patent/CN113132093B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0816—Key establishment, i.e. cryptographic processes or cryptographic protocols whereby a shared secret becomes available to two or more parties, for subsequent use
    • H04L9/0852—Quantum cryptography
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/07—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems
    • H04B10/075—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal
    • H04B10/079—Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems using an in-service signal using measurements of the data signal
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
    • H04B10/70—Photonic quantum communication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
    • H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
    • H04L9/0861—Generation of secret information including derivation or calculation of cryptographic keys or passwords

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Electromagnetism (AREA)
  • Computer Security & Cryptography (AREA)
  • Optics & Photonics (AREA)
  • Theoretical Computer Science (AREA)
  • Optical Communication System (AREA)

Abstract

The invention provides a method and a node for distributing quantum keys, wherein a receiving node receives photons from an emitting node, randomly selects a basis vector as a decoding basis vector of each received photon, measures the photons by using the decoding basis vector of the photons, calculates the relative position of each photon according to the actual position of each photon, replaces the actual position of the received partial or all photons with the relative positions of the photons as the position information of the photons, and finally feeds back the position information of the photons and the decoding basis vector to the emitting node, and the emitting node performs basis vector comparison. When the invention feeds back the position information, the position information of part or all photons is set as the relative position rather than the actual position, and the number of the binary bits required for transmitting the relative position is less than that required for transmitting the actual position, therefore, the proposal provided by the invention can reduce the requirement on bandwidth in the process of quantum key distribution and can carry out quantum key distribution by using lower bandwidth.

Description

Quantum key distribution method and node
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a method and a node for distributing quantum keys.
Background
Quantum Key Distribution (QKD) technology is a technology for securely generating a symmetric Key in two places by using Quantum mechanical characteristics. One implementation of this technique is: the transmitting node encodes a plurality of photons in a photon sequence to be encoded, then sends the photons to a receiving node one by one, aiming at each photon, the receiving node randomly selects a basis vector as a decoding basis vector of the photon, measures the photon by using the decoding basis vector to obtain a measuring result, then the receiving node sends the decoding basis vector and an actual position of each photon to the transmitting node, the transmitting node compares the basis vectors by using the decoding basis vector and the actual position to determine the photon with correct measurement and feeds the photon back to the receiving node, and then the transmitting node and the receiving node can generate a key by using the code corresponding to the photon with correct measurement.
The actual position of the photon is used to represent the position of a photon in the above-mentioned photon sequence, and as the number of photons included in a photon sequence increases, more and more binary bits are required to represent the actual position of each photon in the photon sequence, which results in that the requirement for bandwidth is higher when transmitting the actual positions of multiple photons as the operating frequency of quantum key distribution is higher in the prior art.
Disclosure of Invention
Based on the defects of the prior art, the invention provides a quantum key distribution method and a node, so as to reduce the requirement of the quantum key distribution technology on bandwidth.
To solve the above problems, the following solutions are proposed:
a first aspect of the present application provides a method for distributing quantum keys, including:
the receiving node receives the photon sequence sent by the transmitting node, randomly selects a basis vector from a plurality of preset basis vectors as a decoding basis vector of each received photon, and measures the photon by using the decoding basis vector of the photon to obtain the quantum state of the photon; wherein the sequence of photons comprises a plurality of photons encoded by the transmitting node;
the receiving node calculates, for each received photon, the relative position of the photon according to the actual position of the photon in the sequence of photons and the actual position of the previously received photon in the sequence of photons; wherein, if the photon is the first received photon, the actual position of the previous received photon in the photon sequence refers to a preset synchronous optical position;
the receiving node determines the actual position or the relative position of the photon as the position information of the photon for each received photon; wherein the relative position of at least one of the photons is determined as the position information of the photon;
the receiving node feeds back comparison data of each photon to the transmitting node; the comparison data of each photon comprises position information of the photon, a position information identifier for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon, and a decoding basis vector of the photon;
the receiving node generates a second key according to the quantum state of the correct photon measured in the photon sequence; the photon with correct measurement refers to a photon with the coding basis vector and the decoding basis vector which correspond to each other and are the same basis vector, and the coding basis vector of the photon refers to a basis vector used when the emission node codes the photon.
Optionally, the determining, by the receiving node, an actual position or a relative position of the photon as the position information of the photon for each received photon includes:
the receiving node judges whether the absolute value of the relative position of the photon is larger than a preset threshold value or not aiming at each received photon;
for each received photon, if the absolute value of the relative position of the photon is greater than the threshold, the receiving node determines the actual position of the photon as the position information of the photon;
and for each received photon, if the absolute value of the relative position of the photon is less than or equal to the threshold, the receiving node determines the relative position of the photon as the position information of the photon.
Optionally, the threshold is a threshold calculated according to a transmission bit width of the relative position, the transmission bit width of the relative position is determined according to the detection efficiency and an actual position distribution condition, and the actual position distribution condition is determined by analyzing an actual position of the received photon.
Optionally, the calculating, by the receiving node, for each received photon, a relative position of the photon according to an actual position of the photon in the photon sequence and an actual position of a previous photon of the received photon in the photon sequence by the receiving node includes:
and the receiving node calculates the actual position of the photon in the photon sequence aiming at each received photon and the difference value between the actual positions of the previous photon of the photon received by the receiving node in the photon sequence to obtain the relative position of the photon.
A second aspect of the present application provides a method for distributing quantum keys, including:
the transmitting node transmits the photon sequence to the receiving node; the photon sequence comprises a plurality of photons, the quantum state of each photon is encoded by the emitting node by using the encoding basis vector of the photon, and the encoding basis vector of the photon is any one of the basis vectors randomly selected from a plurality of preset basis vectors by the emitting node;
the transmitting node receives a plurality of comparison data from the receiving node; each piece of comparison data corresponds to a photon, and the comparison data comprises position information of the corresponding photon, position information identification of the photon and decoding basis vector of the photon; wherein the position information identification of the photon is used for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon; a decoded basis vector of the photon, referring to a basis vector used by the receiving node when measuring the photon;
the emission node determines the actual position of the photon corresponding to the comparison data in the photon sequence according to the position information of the comparison data and the position information of the previous comparison data of the comparison data aiming at each comparison data, so as to determine the photon corresponding to the comparison data;
the transmitting node compares the decoding basis vector of the photon with the coding basis vector of the photon aiming at the photon corresponding to each comparison data, so as to determine the photon with correct measurement in the photon sequence; wherein the photons with correct measurement refer to the photons with the corresponding encoding basis vectors consistent with the decoding basis vectors;
the transmitting node generates a first key based on measuring the quantum state of the correct photon in the sequence of photons.
Optionally, the determining, by the transmitting node, an actual position of a photon corresponding to each piece of comparison data in the photon sequence according to the position information of the piece of comparison data and the position information of the piece of comparison data before the piece of comparison data includes:
the transmitting node judges whether the position information of the comparison data is an actual position or a relative position according to the position information identification of the comparison data aiming at each comparison data;
the transmitting node determines the position information of the comparison data as the actual position of the photon corresponding to the comparison data if judging that the position information of the comparison data is the actual position aiming at each comparison data;
and the transmitting node calculates the actual position of the photon corresponding to the comparison data according to the position information of the comparison data and the actual position of the photon corresponding to the previous comparison data of the comparison data if judging that the position information of the comparison data is the relative position aiming at each comparison data.
A third aspect of the present application provides a node, which is a receiving node in a quantum key distribution system, including:
the receiving unit is used for receiving the photon sequence sent by the transmitting node, randomly selecting one basic vector from multiple preset basic vectors as a decoding basic vector of the photon aiming at each received photon, and measuring the photon by using the decoding basic vector of the photon to obtain the quantum state of the photon; wherein the sequence of photons comprises a plurality of photons encoded by the transmitting node;
a calculating unit, configured to calculate, for each received photon, a relative position of the photon according to an actual position of the photon in the photon sequence and an actual position of a previously received photon in the photon sequence; wherein, if the photon is the first received photon, the actual position of the previous received photon in the photon sequence refers to a preset synchronous optical position;
a determining unit, configured to determine, for each received photon, an actual position or a relative position of the photon as position information of the photon; wherein the relative position of at least one of the photons is determined as the position information of the photon;
the transmitting unit is used for feeding back comparison data of each photon to the transmitting node; the comparison data of each photon comprises position information of the photon, a position information identifier for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon, and a decoding basis vector of the photon;
the generating unit is used for generating a second key according to the quantum state of the correct photon measured in the photon sequence; the photon with correct measurement refers to a photon with the coding basis vector and the decoding basis vector which correspond to each other and are the same basis vector, and the coding basis vector of the photon refers to a basis vector used when the emission node codes the photon.
Optionally, the determining unit includes:
the judging unit is used for judging whether the absolute value of the relative position of the photon is larger than a preset threshold value or not aiming at each received photon;
a determining subunit, configured to determine, for each received photon, if an absolute value of a relative position of the photon is greater than the threshold, an actual position of the photon as position information of the photon;
and if the absolute value of the relative position of the photon is less than or equal to the threshold, determining the relative position of the photon as the position information of the photon.
A fourth aspect of the present application provides a node, which is a transmitting node in a quantum key distribution system, including:
a transmitting unit for transmitting the photon sequence to a receiving node; the photon sequence comprises a plurality of photons, the quantum state of each photon is encoded by the emitting node by using the encoding basis vector of the photon, and the encoding basis vector of the photon is any one of the basis vectors randomly selected from a plurality of preset basis vectors by the emitting node;
a receiving unit, configured to receive a plurality of comparison data from the receiving node; each piece of comparison data corresponds to a photon, and the comparison data comprises position information of the corresponding photon, position information identification of the photon and decoding basis vector of the photon; wherein the position information identification of the photon is used for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon; a decoded basis vector of the photon, referring to a basis vector used by the receiving node when measuring the photon;
a determining unit, configured to determine, for each piece of comparison data, an actual position of a photon corresponding to the comparison data in the photon sequence according to position information of the comparison data and position information of a previous comparison data of the comparison data, so as to determine the photon corresponding to the comparison data;
the comparison unit is used for comparing the decoding basis vector of the photon with the coding basis vector of the photon aiming at the photon corresponding to each comparison data, so as to determine the photon with correct measurement in the photon sequence; wherein the photons with correct measurement refer to the photons with the corresponding encoding basis vectors consistent with the decoding basis vectors;
and the generating unit is used for generating a first key according to the quantum state of the correct photon measured in the photon sequence.
Optionally, the determining unit includes:
the judging unit is used for judging whether the position information of the comparison data is an actual position or a relative position according to the position information identification of the comparison data aiming at each comparison data;
the determining subunit is configured to determine, for each piece of comparison data, if it is determined that the position information of the comparison data is an actual position, the position information of the comparison data as an actual position of a photon corresponding to the comparison data;
and the calculating unit is used for calculating the actual position of the photon corresponding to the comparison data according to the position information of the comparison data and the actual position of the photon corresponding to the previous comparison data of the comparison data if the position information of the comparison data is judged to be the relative position according to each comparison data.
The invention provides a method and a node for distributing quantum keys, wherein a receiving node receives photons from an emitting node, randomly selects a basis vector as a decoding basis vector of each received photon, measures the photons by using the decoding basis vector of the photons, calculates the relative position of each photon according to the actual position of each photon, replaces the actual position of the received partial or all photons with the relative positions of the photons as the position information of the photons, and finally feeds back the position information of the photons and the decoding basis vector to the emitting node, and the emitting node performs basis vector comparison. When the invention feeds back the position information, the position information of part or all photons is set as the relative position rather than the actual position, and the number of the binary bits required for transmitting the relative position is less than that required for transmitting the actual position, therefore, the proposal provided by the invention can reduce the requirement on bandwidth in the process of quantum key distribution and can carry out quantum key distribution by using lower bandwidth.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a schematic flowchart of a quantum key distribution method according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of another quantum key distribution method according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a receiving node according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a transmitting node according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The Quantum Key Distribution method provided by the application is mainly suitable for a Quantum Key Distribution (QKD) technology, and in order to better understand the technical scheme provided by the application, firstly, the working principle of the existing QKD technology based on a BB84 protocol is briefly introduced:
first, between two nodes (respectively referred to as a transmitting node and a receiving node) participating in quantum key distribution, the transmitting node keeps time synchronization of the transmitting node and the receiving node by continuously transmitting low-frequency synchronization light to the receiving node.
In one period of synchronous light, the transmitting node generates photons to be encoded one by one at a preset transmitting frequency, each time one photon to be encoded is generated, the code of the photon to be encoded is randomly determined to be 1 or 0, then a base vector is randomly selected from a plurality of preset base vectors to serve as the code base vector of the photon to be encoded, the photon is encoded by using the code base vector, so that the quantum state of the photon is set to be the quantum state corresponding to the code of the photon, and then the encoded photon is sent to the receiving node.
The preset emission frequency is greater than the frequency of the synchronous light.
The corresponding relation between the quantum state of the photon and the code is determined by a preset coding rule.
The transmitting node generates and transmits a plurality of photons to be coded in a synchronous optical period to form a photon sequence.
The receiving node receives the photons emitted by the emitting node one by one, measures and records the actual position of the photon in the photon sequence every time the receiving node receives a photon, randomly selects a basis vector from a plurality of preset basis vectors as a decoding basis vector of the photon, and measures the photon by using the decoding basis vector to obtain a measuring result, namely the quantum state of the photon.
The actual position of a photon in a photon sequence is colloquially understood to mean that this photon is the second photon in the photon sequence. For example, for a quantum key distribution system with a sync light frequency of 100KHz and an emission frequency of 1.25GHz, the emission node generates 12500 photons in a cycle of the sync light, which is equivalent to a sequence of photons emitted by the emission node including 12500 photons, and then the actual positions of the photons in the sequence of photons can be sequentially represented by 0 to 12499.
It will be appreciated that there may be attenuation of photons during transmission, and therefore, a receiving node will typically receive only a portion of the photons in a sequence of photons. Assuming that 10000 photons are received by the receiving node in the photon sequence, after the actual positions of the photons are measured by the receiving node, the actual positions of each received photon and the selected decoding basis vector need to be fed back to the transmitting node as comparison data.
After 10000 pieces of comparison data fed back by the receiving node are received, for each piece of comparison data, the transmitting node determines which photon in the photon sequence corresponds to the piece of comparison data according to the actual position in the piece of comparison data, and then the transmitting node can compare the coding basis vector of the photon selected by the transmitting node with the decoding basis vector carried in the piece of comparison data to determine whether the coding basis vector is consistent with the decoding basis vector carried in the piece of comparison data. For any photon, if the transmitting node determines that the decoding basis vector used by the receiving node and the coding basis vector used by the transmitting node are the same basis vector according to the corresponding comparison data, the transmitting node determines that the photon is the photon with correct measurement.
After determining all the correctly measured photons in a photon sequence, the transmitting node sends the actual positions of the correctly measured photons to the receiving node, and similarly, the receiving node can also determine which photons in the current photon sequence are the correctly measured photons according to the received actual positions.
And finally, the transmitting node and the receiving node determine whether the code of each photon with correct measurement in the current photon sequence is 0 or 1 by using a preset coding rule, so that the codes of the photons with correct measurement in the current photon sequence are arranged according to the actual position to form a binary string, and the binary string can be used as a key for encrypting and decrypting subsequent information interaction of the transmitting node and the receiving node.
The existing quantum key distribution method has the following defects:
in the above process, the receiving node needs to send the actual position of each photon received by the receiving node to the transmitting node, and in combination with the foregoing example, in a photon sequence including 12500 photons, the range of the actual position of the photon is 0 to 12499, when the photon sequence is converted into a binary system for transmission, each comparison data needs to carry the binary system including 14 binary bits (i.e., 14 bits) for representing the actual position, and the number of comparison data to be transmitted for one photon sequence is also large, which results in a classical channel having a sufficiently large bandwidth being required to be configured between the transmitting node and the receiving node to ensure that the comparison data can be sent from the receiving node to the transmitting node in time, thereby resulting in a high implementation cost of the existing quantum key distribution technology.
Based on the above drawbacks of the prior art, an embodiment of the present application provides a quantum key distribution method, which includes the following steps, with reference to fig. 1:
s101, the transmitting node sends the photon sequence to the receiving node.
Wherein the photon sequence comprises a plurality of photons, each photon being encoded by the emitting node with the encoding basis vector of the photon.
Specifically, for each photon in the photon sequence, the coding basis vector of the photon is any one of the basis vectors randomly selected from a plurality of preset basis vectors when the emission node needs to code the photon.
As in the previous description of the prior art, the sequences of photons referred to in this application refer to all encoded photons transmitted by the transmitting node within one synchronization light period.
Taking the QKD technique based on four polarization states as an example, the process by which each photon in a sequence of photons is encoded by the transmitting node is:
first, it is explained that each two mutually orthogonal polarization states constitute a basis vector. For any one basis vector, one photon can be coded into any one of two polarization states corresponding to the basis vector by using the basis vector, but cannot be coded into other polarization states except the two polarization states. Thus, in this example, two vectors are available for selection, each corresponding to two of the four states of polarization that are orthogonal to each other.
The transmitting node randomly determines whether the code corresponding to the photon (marked as the photon to be coded) which needs to be coded currently is 0 or 1, if the determined code is 1, then the transmitting node selects any one of the two basis vectors as the coding basis vector of the photon to be coded, and finds out the coding basis vector from a preset coding rule, which polarization state is used for representing 1 in the two polarization states corresponding to the selected coding basis vector, and finally the photon to be coded is coded into the corresponding polarization state by using the coding basis vector, so that the coding of one photon to be coded is completed.
Specifically, it is assumed that the four polarization states are respectively denoted as a polarization state a, a polarization state B, a polarization state C, and a polarization state D, where the polarization state a and the polarization state B are orthogonal to each other to form a first basis vector, the polarization state C and the polarization state D are orthogonal to each other to form a second basis vector, and the encoding rule specifies that the code 1 corresponds to the polarization state a and the polarization state C, and the code 0 corresponds to the polarization state B and the polarization state D.
Based on the above assumptions, if the transmitting node determines that the code of one photon to be coded is 1, and selects the second basis vector as the coding basis vector of the photon to be coded, according to the coding rule, the transmitting node codes the photon to be coded into the polarization state C by using the second basis vector, thereby completing the coding of the photon to be coded.
It should be noted that the polarization state of the photon is one of the quantum states of the photon, and the QKD technology may be implemented based on the polarization state of the photon, or based on other quantum states of the photon, and, in contrast, the method provided by the present application may be applicable to the QKD technology implemented based on the polarization state, or to the QKD technology implemented based on other quantum states of the photon.
For ease of understanding, the methods that follow the present application will be described in connection with the above-described QKD technique based on four polarization states.
In a QKD system, the transmitting node and the receiving node are configured with the same encoding rules.
Finally, it should be noted that the sending of the photon sequence in step S101 means that the sending node generates and codes photons one by one at a preset sending frequency when a synchronous optical cycle starts, and sends the coded photons to the receiving node every time a photon is coded. After the current synchronous light period is finished, all the coded photons emitted by the emitting node form a photon sequence.
S102, the receiving node receives the photon sequence sent by the transmitting node, and measures each received photon to obtain the quantum state of the received photon.
Similar to the foregoing step S101, step S102 means that the receiving node receives the coded photons sent by the transmitting node within one synchronization optical period one by one.
For each photon received, the process by which the receiving node measures that photon is:
randomly selecting a basis vector from a plurality of preset basis vectors as a decoding basis vector of the photon, and measuring the photon by using the decoding basis vector of the photon.
Similar to the encoding process of a photon, after a basis vector for measuring the photon is determined for any one photon, the result obtained by the measurement can only be one of two quantum states corresponding to the determined basis vector.
In combination with the foregoing example provided based on four polarization states, for a photon to be measured, if the receiving node selects the first basis vector as the decoded basis vector of the photon, the measured polarization state can only be one of the two polarization states (polarization state a and polarization state B) corresponding to the first basis vector, and if the decoded basis vector is the second basis vector, the measured polarization state can only be one of the two polarization states (polarization state C and polarization state D) corresponding to the second basis vector.
For a photon needing to be measured, assuming that the coding basis vector selected when the transmitting node codes the photon is the first basis vector, the polarization state of the photon is coded into the polarization state a by using the first basis vector, and the decoding basis vector selected by the receiving node for the photon is also the first basis vector, then on the premise that the transmission process of the photon from the transmitting node to the receiving node is not interfered, the polarization state of the photon which can be measured by the transmitting node is the polarization state a coded by the transmitting node.
In contrast, for a photon, if the coding basis vector used by the transmitting node is the first basis vector and the decoding basis vector used by the receiving node is the second basis vector, the polarization state measured by the receiving node is not the polarization state coded by the transmitting node, but any one of the two polarization states corresponding to the second basis vector.
S103, the receiving node calculates the relative position of each received photon.
Specifically, after receiving a photon, the receiving node may measure an actual position of the photon in the photon sequence where the photon is located. For each photon received by the receiving node, the receiving node may use the actual position of the photon to subtract the actual position of the previously received photon, and the resulting calculation is the relative position of the photon.
The actual position of the photon is used to indicate that this photon is the few photons in the sequence of photons emitted by the emitting node. Taking the aforementioned QKD system with an emission frequency of 1.25GHz and a synchronous optical frequency of 100KHz as an example, the transmitting node encodes and transmits 12500 photons in one synchronous optical period, the 12500 photons forming a photon sequence. If the actual position of a certain photon measured by the receiving node is 6999, it indicates that this photon is the 7000 th photon emitted in the current synchronous optical cycle.
In particular, for the first photon received by the receiving node, the predetermined synchronization light position may be determined as the actual position of the photon received immediately before this photon. Wherein the synchronous light position may be set to 0 in advance.
Specifically, the receiving node may calculate that the received photon is the second photon in the sequence of photons sent by the transmitting node by using the time of receiving a photon and the start time of the current synchronous optical period.
Still taking the QKD system with the transmission frequency of 1.25GHz and the synchronous optical frequency of 100KHz as an example, when the transmitting node sends the coded photons to the receiving node one by one based on the transmission frequency at the beginning of a synchronous optical period, it can be understood that the time interval T between every two photons transmitted by the transmitting node is equal to 1 second divided by 1.25G, that is, 0.8 × 10G-9And second. Generally, when the transmitting node transmits a photon sequence, the first photon in the photon sequence is transmitted at the beginning of the synchronization optical cycle, and then one photon is transmitted at each time interval until the current synchronization optical cycle is finished.
Therefore, the receiving node may record the start time of each synchronization optical cycle in real time, if a photon is received by the receiving node in any synchronization optical cycle, the receiving node may calculate a difference between the time T1 when the photon is received and the start time T0 of the current synchronization optical cycle, if the difference between the two is 0, that is, the time T1 when the photon is received is equal to the start time T0 of the current synchronization optical cycle, which indicates that the photon is the first photon in the photon sequence sent by the transmitting node, and the actual position of the photon in the photon sequence is 0, and if the difference between the two is not 0, the actual position of the photon in the photon sequence is obtained by dividing the time interval T when the transmitting node sends the photon by the difference obtained by subtracting T0 from T1. For example, if the difference obtained by subtracting T0 from T1 is divided by the time interval T to obtain 5999, it indicates that this photon is the 6000 th photon in the sequence of photons sent by the transmitting node, and its actual position is recorded as 5999.
In this embodiment, the difference between the actual position of a photon and the actual position of the previously received photon may be used as the relative position of the photon.
In a specific example, it is assumed that the receiving node receives the 900 th photon in the photon sequence emitted by the emitting node at a certain time within a certain synchronization optical period, and its actual position is 899, and then receives the 910 photons in the photon sequence, and its actual position is 909, the middle 9 photons are not received by the receiving node due to attenuation in the transmission process, and the receiving node subtracts the actual position of the 900 th photon from the actual position of the 910 th photon, i.e. 909 minus 899, to obtain the relative position of the 910 th photon as 10.
The above example can be regarded as an ideal positional relationship between two adjacent photons received by the receiving node when the detection efficiency of the receiving node is 10%. The detection efficiency is used for indicating the proportion of photons successfully received by the receiving node in a photon sequence. It will be appreciated that if the detection efficiency of the photon sequence emitted in a certain synchronous optical period is close to 10%, the position relationship between two adjacent successfully received photons when the receiving node calculates the relative position will be close to the position relationship in the above example, and correspondingly, the relative position of each successfully received photon calculated based on the above method will be generally close to 10.
And S104, determining the actual position or the relative position of each received photon as the position information of the photon by the receiving node.
Wherein the relative position of at least one photon is determined as the position information of the photon;
the purpose of step S104 is to determine the relative positions of some or all of the measurable photons as corresponding position information and the actual positions of other photons as corresponding position information for all the measurable photons.
For specific determination of which photons are to be determined as corresponding position information and which photons are to be determined as actual positions as position information, the determination may be performed according to a preset rule, for example, a threshold may be determined, if the calculated relative position of one photon is greater than or equal to the threshold, the actual position of the photon is determined as position information, and if the calculated relative position of one photon is less than or equal to the threshold, the relative position of the photon is determined as position information.
S105, the receiving node feeds back comparison data of each photon to the transmitting node.
The comparison data of each photon comprises the position information of the photon, a position information identifier for indicating whether the position information of the photon is an actual position or a relative position, and a decoding basis vector of the photon.
The transmitting node can judge whether the position information recorded in the received comparison data is the actual position or the relative position of the corresponding photon according to the position information identifier, and then correspondingly process the position information in the comparison data to obtain the actual position of the photon corresponding to the comparison data, and further determine that the comparison data corresponds to the several photons in the transmitted photon sequence.
S106, the transmitting node determines the actual position of the corresponding photon according to the position information of the comparison data and the position information of the previous comparison data aiming at each comparison data.
As described in step S105, each piece of comparison data carries the position information and the position information identifier of the corresponding photon.
When step S106 is executed, for the first comparison data received by the transmitting node, if the position information identifier in the comparison data indicates that the position information carried by the first comparison data is the actual position, directly determining the position information carried by the comparison data as the position of the first photon received by the receiving node; and if the position information identifier of the first comparison data indicates that the position information carried by the first comparison data is a relative position, calculating the actual position of the corresponding photon according to the position information carried by the first comparison data and a preset synchronous light position.
For example, if the position information carried by the first alignment data received by the transmitting node is 49 and the position information is the actual position, it indicates that the first alignment data corresponds to the 50 th photon in the photon sequence. If the position information 49 is a relative position and the relative position is calculated by the method in step S103, the actual position of the photon corresponding to the first comparison data is the sum of the position information 49 and the preset synchronization light position, and particularly, if the synchronization light position is preset to 0, the actual position of the photon corresponding to the first comparison data is also 49, which indicates that the first comparison data corresponds to the 50 th photon of the photon sequence.
For each subsequent alignment data, the transmitting node may process in a similar manner. For example, the position information of one alignment datum is N1, and if the position information is the actual position, the actual position of the photon corresponding to the alignment datum is N1, which is the N1+1 th photon in the photon sequence.
If the position information is a relative position, and the actual position of the photon corresponding to the previous alignment data is calculated to be N2 according to the position information of the previous alignment data, in an embodiment in which the difference between the actual positions of the two photons is used as the relative position, the current position information N1 of the alignment data may be added to the actual position N2 of the photon corresponding to the previous alignment data, so as to determine that the actual position of the photon corresponding to the current alignment data in the photon sequence is N1+ N2, which indicates that the corresponding photon is the N1+ N2+1 th photon in the photon sequence.
S107, the transmitting node compares the decoding basis vector and the coding basis vector of the photon corresponding to each comparison data, and therefore the correct photon in the photon sequence is determined.
As mentioned before, the actual position of a photon is used to indicate that this photon is the second photon in the sequence of photons emitted by the emitting node. Therefore, through step S106, the transmitting node can determine which photon in the emitted photon sequence corresponds to each comparison data, and then can compare the encoding basis vector of the photon recorded by the transmitting node with the decoding basis vector carried in the comparison data corresponding to the photon.
For any photon received by the receiving node, if the encoding basis vector used when the transmitting node encodes the photon is consistent with the decoding basis vector used when the receiving node measures the photon, the transmitting node determines the photon as the photon with correct measurement; in contrast, if the encoding basis vector and the decoding basis vector of a photon do not coincide, the photon is not the correct photon to measure.
Taking the QKD implemented by using four polarization states in step S101 as an example, assuming that a decoding basis vector carried in one piece of comparison data received by the transmitting node is a first basis vector, and the transmitting node determines that the comparison data corresponds to the 500 th photon of the photon sequence by executing step S106, and then the transmitting node queries its own record to find that the 500 th photon in the emitted photon sequence is encoded by using the first basis vector as an encoding basis vector, then the 500 th photon of the photon sequence corresponding to the comparison data is the correct photon to be measured.
It should be noted that, when step S106 and step S107 are executed, the transmitting node may determine the actual position of the photon corresponding to the comparison data every time it receives one comparison data, and execute step S107 to compare the encoding basis vector and the decoding basis vector of the photon corresponding to the comparison data. It is also possible to start executing step S106 and step S107 in sequence after all the comparison data are received.
The process from step S102 to step S107 can be understood as follows:
the receiving node measures each photon received by the receiving node in the photon sequence, and informs the transmitting node of the relative position or the actual position of the photon received by the receiving node, which photons in the photon sequence are received by the receiving node, and which basis vector is respectively used as a decoding basis vector when the receiving node measures the photons.
After the transmitting node determines which photons in the photon sequence are received by the receiving node and the coding basis vectors used by the receiving node when the receiving node measures the photons, basis vector comparison can be performed on the photons received by the receiving node, that is, the coding basis vectors and the decoding basis vectors of the photons received by the receiving node are compared, so that the photons with the decoding basis vectors and the coding basis vectors consistent in the photons received by the receiving node are determined as the photons with correct measurement.
And S108, the emitting node generates a first key according to the quantum state of the photon with correct measurement.
Step S101 indicates that the QKD system is configured with preset encoding rules for specifying the correspondence between the quantum states of the photons and the binary encoding.
After the emission node determines the photons with correct measurement, the emission node can directly determine which quantum state the photons with correct measurement are coded into by using the record of the emission node, further determine whether the binary code corresponding to each photon with correct measurement is 0 or 1 according to the coding rule, and finally arrange the binary codes corresponding to the photons into a binary sequence according to the actual positions of the photons with correct measurement in the photon sequence, wherein the binary sequence is the first key.
And S109, the receiving node generates a second key according to the quantum state of the photon with correct measurement.
After determining the photons with correct measurement, the transmitting node can send the actual positions of the photons with correct measurement in the photon sequence to the receiving node, so that the receiving node can determine which photons in the photons with correct measurement are the photons with correct measurement.
Similar to the transmitting node, after determining which of the photons received and measured by the receiving node are the photons with correct measurement, the receiving node can determine the binary code corresponding to each photon with correct measurement according to the quantum state of the photons by using the same coding rule as that of the transmitting node, arrange the corresponding binary codes according to the actual position sequence of the photons with correct measurement in the photon sequence, and obtain a binary sequence, wherein the binary sequence generated by the receiving node is the second key.
If a photon is not interfered in the process of transmitting from the transmitting node to the receiving node, and the encoding basis vector used by the transmitting node and the decoding basis vector used by the receiving node are the same basis vector, then the quantum state of the photon measured by the receiving node is the quantum state encoded by the transmitting node,
in connection with the QKD system based on four polarization states in the foregoing example, if the transmitting node encodes a photon into polarization state a using the first basis vector, and after the photon is transmitted to the receiving node without interference, the receiving node also measures the photon using the first basis vector, then the measured polarization state is also polarization state a. Considering that the transmitting node and the receiving node are configured with the same encoding rule, it can be understood that, for an undisturbed photon with correct measurement, the binary codes corresponding to the photon determined by the transmitting node and the receiving node are the same, and the two nodes arrange the binary codes of the photons with correct measurement into a binary sequence based on the same order. Therefore, based on the method provided in the foregoing embodiment, the first key generated by the transmitting node and the second key generated by the receiving node are the same key, and both sides can encrypt the information to be transmitted and decode the received encrypted information based on the key pairs generated by the both sides.
Optionally, in other embodiments of the present application, the method described in the above embodiments may also be performed multiple times between the transmitting node and the receiving node, so as to generate multiple binary sequences, and the binary sequences are combined to form the key.
With reference to the method for calculating the relative position in step S103 and the specific example, it can be understood that, as long as the detection efficiency of the currently transmitted photon sequence satisfies a certain condition, except for a few specific examples that may exist (a case that the difference between the actual positions of two successfully received photons is very large even at a detection efficiency of 10%, which results in the relative position of one of the photons being much greater than 10), the value range of the relative position of the photon calculated in this embodiment will be much smaller than the value range of the actual position of the photon in the existing QKD technology.
Referring to the example of step S103, at a detection efficiency of 10%, the average value of the relative position of each photon is 10, and then, when the relative position is transmitted, considering that there may be a float in the value, it is sufficient to set the value range of the relative position to 0 to 20 to cover the relative position of most photons received by the receiving node. This means that only 5 binary bits need to be set in each comparison data to represent the relative position of most photons, and one binary bit is added as a position information identifier, and 6 binary bits can represent the relative position of most photons.
Further, with the improvement of the detection efficiency, the difference of the actual positions between every two adjacent photons successfully received by the receiving node is reduced, so that the bandwidth required by the data transmission process can be further reduced by the method provided by the application. In an ideal case, assuming that the detection efficiency reaches 100%, the difference between the actual positions of every two adjacent photons received by the receiving node is 1, and only one binary bit is needed to represent the relative position of one photon.
Another embodiment of the present application further provides a method for distributing quantum keys, please refer to fig. 2, where the method includes the following steps:
s201, the transmitting node sends the photon sequence to the receiving node.
S202, the receiving node receives the photon sequence sent by the transmitting node, and measures each received photon to obtain the quantum state of the received photon.
Alternatively, existing receiving nodes for implementing QKD techniques are typically configured with a light sensitive element called an Avalanche Photodiode (APD), which can measure each photon received using the APD.
S203, the receiving node calculates the relative position of each received photon.
S204, the receiving node judges whether the relative position of each received photon meets a preset condition.
For a photon received by each receiving node in the photon sequence, if the relative position of the photon satisfies the predetermined condition, step S205 is executed, and if the relative position of the photon does not satisfy the predetermined condition, step S206 is executed.
Wherein the preset condition is that the relative position of the photon is less than or equal to a preset threshold value.
That is to say, for a photon received by each receiving node in the photon sequence, if the relative position of the photon is less than or equal to the preset threshold, it is determined that the photon meets the preset condition, step S205 is performed on the photon, and if the relative position of the photon is greater than the preset threshold, it is determined that the photon does not meet the preset condition, and step S206 is performed on the photon.
Optionally, the threshold preset in step S204 may be obtained by calculating based on the relative position transmission bit width by using the following formula.
X＝2a
Wherein, X represents a preset threshold value, and a represents a relative position transmission bit width. The relative position transmission bit width is a positive integer determined according to the detection efficiency and the actual position distribution, and the determined relative position transmission bit width is smaller than the number of binary bits required when the actual position of the photon is represented by a binary number. The relative position transmission bit width indicates the number of binary bits required for transmitting the relative position, and may also be considered as a bandwidth occupied when the relative position is transmitted, and the higher the detection efficiency is, the smaller the relative position transmission bit width is, the smaller the bandwidth required for transmitting the relative position is.
As mentioned above, the detection efficiency refers to the proportion of photons received by the receiving node in the photons emitted by the emitting node in a synchronous optical period.
The actual position distribution refers to the distribution of the actual positions of the photons received by the receiving node in the sequence of photons emitted by the emitting node.
For example, assuming that the detection efficiency in a certain synchronization light period is 20%, it means that only 20% of the photons in the sequence of photons emitted by the emitting node are successfully received by the receiving node in this synchronization light period.
In this case, if the photons received by the receiving nodes are completely and uniformly distributed in the photon sequence, the difference between the actual positions of the photons received by every two adjacent receiving nodes is 5, for example, the transmitting node starts to transmit the photons one by one, after the receiving node receives the 1 st photon sent by the transmitting node, the subsequent 2 nd to 5 th photons are not received by the receiving node, then the receiving node receives the 6 th photon, the subsequent 7 th to 10 th photons are not received, then the 11 th photon, the 16 th photon, the 21 st photon is received by the receiving node in sequence, and the rest are not received, and so on.
Obviously, in this case, if the difference between the actual positions of the photons received by two adjacent receiving nodes is taken as the relative position of the photon, the relative position of the 1 st photon received by the receiving node is 0, and the relative position of each subsequent photon is 5. In this ideal case, only three binary bits are needed to represent the relative position of each photon received by the receiving node, and therefore the relative position transmission bit width can be set to 3.
In contrast, if the distribution of photons received by the receiving node in the photon sequence sent by the transmitting node is not uniform in a certain synchronous optical period under the detection efficiency of 20%, the difference between the actual positions of the photons received by every two adjacent receiving nodes may fluctuate within a certain range, and at this time, the transmission bit width of the relative position needs to be correspondingly increased to cover the value range of the relative positions of most photons.
For example, if the amplitude of the fluctuation is small and the values of the relative positions of most photons are less than or equal to 10, then the three binary bits obviously cannot cover the value range of 1 to 10, and at this time, the transmission bit width of the relative position can be set to 4, so that most photons received by the receiving node can use the relative position as the position information.
According to the above example, it can be understood that, in a synchronization optical period, the detection efficiency and the actual position distribution jointly determine the value range of the relative position of each photon, and after the detection efficiency is determined, the values of the relative positions of all photons received by the receiving node in a synchronization optical period reflect the actual position distribution in the synchronization optical period.
If the detection efficiency in a certain synchronization light period is 1/N, which means that in this synchronization light period, an emitting node can successfully receive a photon every N photon receiving nodes on average, at this time, the relative position transmission bit width can be initially set to the number of binary bits required for representing the number N, for example, N is less than or equal to 8, three binary bits are required to represent N, the relative position transmission bit width is initially set to 3, N is greater than 8 but less than or equal to 16, four binary bits are required to represent N, and the relative position transmission bit width is initially set to 4.
Further, based on the relative position transmission bit width preliminarily determined according to the detection efficiency, the receiving node may count a value of the relative position of each photon received by the receiving node in the synchronous optical cycle, adaptively adjust the preliminarily set transmission bit width according to a statistical result, finally determine the relative position transmission bit width matched with the synchronous optical cycle, and further determine the corresponding threshold.
In an optional embodiment of the present application, when the transmitting node and the receiving node perform quantum key distribution in a synchronous optical cycle, the receiving node may determine, according to the detection efficiency and the actual position distribution condition in the last several quantum key distribution processes, a relative position transmission bit width of the current quantum key distribution process, and agree with the transmitting node, and then send the relative position of a photon to the transmitting node based on the agreed relative position transmission bit width.
In another optional embodiment, after the current synchronization optical cycle is ended, the receiving node may determine the relative position transmission bit width corresponding to the current quantum key distribution process according to the detection efficiency and the actual position distribution condition in the synchronization optical cycle, and then determine which photons are transmitted as position information based on the relative position transmission bit width.
S205, the receiving node determines the relative position of the photon meeting the condition as the position information of the photon.
S206, the receiving node determines the actual position of the photon which does not meet the condition as the position information of the photon.
It should be noted that steps S205 and S206 are performed for each photon received by the receiving node in the photon sequence. That is, for each photon received by the receiving node, after the receiving node performs the determination of step S204, step S205 or step S206 is specifically performed according to whether the relative position of the photon is less than or equal to the preset threshold.
S207, the receiving node feeds back comparison data of each photon to the transmitting node.
Each piece of feedback comparison data carries the decoding basis vector, the position information and the position information identification of the photon corresponding to the comparison data.
Optionally, one binary bit in the comparison data may be used as the position information identifier, and if the position information carried in the comparison data is the actual position of the corresponding photon, the binary bit representing the position information identifier is set to 1, and if the position information carried in the comparison data is the relative position of the corresponding photon, the binary bit is set to 0.
The transmitting node and the receiving node can agree in advance specifically to which binary bit in the comparison data is to be used as the position information identifier. For example, if the first binary bit of each piece of comparison data is agreed to be used as the position information identifier, after the transmitting node receives the comparison data, it can determine whether the actual position or the relative position of the corresponding photon is carried in the comparison data according to whether the first binary bit of the comparison data is 1 or 0.
And S208, the transmitting node determines the actual position of the corresponding photon according to the position information of the comparison data and the position information of the previous comparison data aiming at each comparison data.
The specific implementation process of this step is consistent with step S106 in the embodiment corresponding to fig. 1, and is not described here again.
S209, the transmitting node compares the decoding basis vector and the coding basis vector of the photon corresponding to each comparison data, so as to determine the correct photon to be measured in the photon sequence.
The correct photon is measured, referring to a photon where the decoded basis vector and the encoded basis vector coincide.
S210, the transmitting node sends the actual position of the photon with correct measurement to the receiving node.
The receiving node may determine which photons of the received photons are the photons with the correct measurement according to the actual received position, and then execute step S212 based on the photons with the correct measurement.
S211, the emitting node generates a first key according to the quantum state of the photon with correct measurement.
The quantum state of the photon with correct measurement in step S211 is the quantum state of the emission node encoded by the encoding basis vector.
S212, the receiving node generates a second key according to the quantum state of the photon with correct measurement.
The quantum state of the photon with correct measurement in step S212 is the quantum state obtained by using the decoding basis vector measurement after the receiving node receives the photon.
As in the corresponding embodiment of fig. 1, the transmitting node and the receiving node share the same set of encoding rules.
For the photons with correct measurement, the quantum state after the encoding of the transmitting node is the quantum state measured by the receiving node, and the encoding rules used for dual-transmission are the same, so that the first key generated by the transmitting node and the second key generated by the receiving node are the same key. Subsequently transmitted messages may be encrypted and decrypted based on this key.
Based on the foregoing quantum key distribution method provided in the embodiment of the present application, an embodiment of the present application provides a receiving node of a quantum key distribution system, please refer to fig. 3, where the receiving node includes:
the receiving unit 301 is configured to receive a photon sequence sent by the transmitting node, randomly select one basis vector from multiple preset basis vectors as a decoding basis vector of a photon for each received photon, and measure the photon by using the decoding basis vector of the photon.
Wherein the sequence of photons comprises a plurality of photons encoded by the emitting node.
A calculating unit 302, configured to calculate, for each received photon, a relative position of the photon according to an actual position of the photon in the photon sequence and an actual position of a previously received photon in the photon sequence.
If the photon is the first received photon, the actual position of the previous received photon in the photon sequence refers to the preset synchronous optical position.
A determining unit 303 for determining an actual position or a relative position of the photon for each received photon as position information of the photon.
Wherein the relative position of at least one photon is determined as the position information of the photon.
A sending unit 304, configured to feed back the comparison data of each photon to the transmitting node.
The comparison data of each photon comprises position information of the photon, position information identification for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon, and a decoding basis vector of the photon.
A generating unit 305 for generating a second key based on the measured correct quantum state of the photon in the sequence of photons.
The correct photon is measured to indicate that the corresponding encoding basis vector and the decoding basis vector are photons of the same basis vector, and the encoding basis vector of the photon is the basis vector used when the emission node encodes the photon.
The second key generated by the generating unit 305 may be provided to the receiving unit 301, so that the receiving unit 301 decrypts the encrypted message sent by the transmitting node by using the second key.
Optionally, the determining unit 303 includes:
and the judging unit is used for judging whether the absolute value of the relative position of the photon is greater than a preset threshold value or not aiming at each received photon.
And the determining subunit is used for determining the actual position of the photon as the position information of the photon if the absolute value of the relative position of the photon is greater than the threshold value for each received photon.
And if the absolute value of the relative position of the photon is less than or equal to the threshold value, determining the relative position of the photon as the position information of the photon.
The threshold may be calculated according to a transmission bit width of the relative position. The relative position transmission bit width can be determined according to the detection efficiency and the actual position distribution condition of photons in the synchronous light period.
When the calculating unit 302 calculates the relative position of the photon, it is specifically configured to:
and calculating the actual position of the photon in the photon sequence and the difference value between the actual positions of the previous photon of the photon received by the receiving node in the photon sequence aiming at each received photon to obtain the relative position of the photon.
Another embodiment of the present application further provides a transmitting node, where the transmitting node is a transmitting node in a quantum key distribution system, please refer to fig. 4, where the transmitting node includes:
a sending unit 401, configured to send the photon sequence to a receiving node.
The photon sequence comprises a plurality of photons, each photon is coded by the emitting node by using the coding basis vector of the photon, and the coding basis vector of the photon is any one basis vector selected from a plurality of preset basis vectors by the emitting node.
A receiving unit 402, configured to receive a plurality of comparison data from a receiving node.
Each piece of comparison data corresponds to one photon, and the comparison data comprises corresponding photon position information, photon position information identification and photon decoding basis vector.
Wherein the position information identification of the photon is used for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon; the decoded basis vector of a photon refers to the basis vector used by the receiving node when measuring the photon.
A determining unit 403, configured to determine, for each piece of comparison data, an actual position of a photon corresponding to the comparison data in the photon sequence according to the position information of the comparison data and the position information of the previous comparison data of the comparison data, so as to determine the photon corresponding to the comparison data;
and a comparing unit 404, configured to compare, for each photon corresponding to the comparison data, the decoded basis vector of the photon with the encoded basis vector of the photon, so as to determine a photon with a correct measurement in the photon sequence.
Wherein, the correct photon is measured and refers to the photon with the corresponding encoding basis vector consistent with the decoding basis vector.
A generating unit 405 for generating a first key based on the measured correct quantum state of the photon in the sequence of photons.
Optionally, the determining unit 403 includes:
and the judging unit is used for judging that the position information of the comparison data is an actual position or a relative position according to the position information identifier of the comparison data aiming at each comparison data.
And the determining subunit is used for determining the position information of the comparison data as the actual position of the photon corresponding to the comparison data if the position information of the comparison data is determined to be the actual position for each comparison data.
And the calculating unit is used for calculating to obtain the actual position of the photon corresponding to the comparison data according to the position information of the comparison data and the actual position of the photon corresponding to the previous comparison data of the comparison data if the position information of the comparison data is judged to be the relative position according to each comparison data.
After the generating unit 405 generates the first key, the sending unit 401 may call the first key generated by the generating unit 405, encrypt a message to be sent by using the first key, and then send the encrypted message to the receiving node.
The working principle of the transmitting node provided in this embodiment is consistent with the corresponding steps in the quantum key distribution method provided in other embodiments of the present application, and is not described here again.
The invention provides a transmitting node and a receiving node in a quantum key distribution system, wherein the receiving node receives photons from the transmitting node by using a receiving unit 301, randomly selects a basis vector as a decoding basis vector of each photon and measures the photons by using the decoding basis vector of the photon, a calculating unit 302 calculates the relative position of each photon according to the actual position of each photon, a determining unit 303 replaces the actual position of the photons with the relative positions of the photons as the position information of the photons for part or all of the received photons, and finally a sending unit 304 feeds back the position information of the photons and the decoding basis vector to the transmitting node to be compared by the transmitting node. When the invention feeds back the position information, the position information of part or all photons is set as the relative position rather than the actual position, and the number of the binary bits required for transmitting the relative position is less than that required for transmitting the actual position, therefore, the proposal provided by the invention can reduce the requirement on bandwidth in the process of quantum key distribution and can carry out quantum key distribution by using lower bandwidth.
Those skilled in the art can make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A method for distributing quantum keys, comprising:
the receiving node receives the photon sequence sent by the transmitting node, randomly selects a basis vector from a plurality of preset basis vectors as a decoding basis vector of each received photon, and measures the photon by using the decoding basis vector of the photon to obtain the quantum state of the photon; wherein the sequence of photons comprises a plurality of photons encoded by the transmitting node;
the receiving node calculates, for each received photon, the relative position of the photon according to the actual position of the photon in the sequence of photons and the actual position of the previously received photon in the sequence of photons; wherein, if the photon is the first received photon, the actual position of the previous received photon in the photon sequence refers to a preset synchronous optical position;
the receiving node determines the actual position or the relative position of the photon as the position information of the photon for each received photon; wherein the relative position of at least one of the photons is determined as the position information of the photon;
the receiving node feeds back comparison data of each photon to the transmitting node; the comparison data of each photon comprises position information of the photon, a position information identifier for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon, and a decoding basis vector of the photon;
the receiving node generates a second key according to the quantum state of the correct photon measured in the photon sequence; the photon with correct measurement refers to a photon with the coding basis vector and the decoding basis vector which correspond to each other and are the same basis vector, and the coding basis vector of the photon refers to a basis vector used when the emission node codes the photon.
2. The method for distributing the quantum key according to claim 1, wherein the receiving node determines, for each received photon, an actual position or a relative position of the photon as the position information of the photon, and comprises:
the receiving node judges whether the absolute value of the relative position of the photon is larger than a preset threshold value or not aiming at each received photon;
for each received photon, if the absolute value of the relative position of the photon is greater than the threshold, the receiving node determines the actual position of the photon as the position information of the photon;
and for each received photon, if the absolute value of the relative position of the photon is less than or equal to the threshold, the receiving node determines the relative position of the photon as the position information of the photon.
3. The method according to claim 2, wherein the threshold is a threshold calculated according to a relative position transmission bit width determined according to the detection efficiency and an actual position distribution determined by analyzing an actual position of the received photon.
4. The method of claim 1, wherein the receiving node calculates, for each received photon, a relative position of the photon according to an actual position of the photon in the sequence of photons and an actual position of a previous photon of the photons received by the receiving node in the sequence of photons, and comprises:
and the receiving node calculates the actual position of the photon in the photon sequence aiming at each received photon and the difference value between the actual positions of the previous photon of the photon received by the receiving node in the photon sequence to obtain the relative position of the photon.
5. A method for distributing quantum keys, comprising:
the transmitting node transmits the photon sequence to the receiving node; the photon sequence comprises a plurality of photons, the quantum state of each photon is encoded by the emitting node by using the encoding basis vector of the photon, and the encoding basis vector of the photon is any one of the basis vectors randomly selected from a plurality of preset basis vectors by the emitting node;
the transmitting node receives a plurality of comparison data from the receiving node; each piece of comparison data corresponds to a photon, and the comparison data comprises position information of the corresponding photon, position information identification of the photon and decoding basis vector of the photon; wherein the position information identification of the photon is used for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon; a decoded basis vector of the photon, referring to a basis vector used by the receiving node when measuring the photon;
the emission node determines the actual position of the photon corresponding to the comparison data in the photon sequence according to the position information of the comparison data and the position information of the previous comparison data of the comparison data aiming at each comparison data, so as to determine the photon corresponding to the comparison data;
the transmitting node compares the decoding basis vector of the photon with the coding basis vector of the photon aiming at the photon corresponding to each comparison data, so as to determine the photon with correct measurement in the photon sequence; wherein the photons with correct measurement refer to the photons with the corresponding encoding basis vectors consistent with the decoding basis vectors;
the transmitting node generates a first key based on measuring the quantum state of the correct photon in the sequence of photons.
6. The method for distributing the quantum key according to claim 5, wherein the determining, by the transmitting node, for each alignment data, the actual position of the photon corresponding to the alignment data in the photon sequence according to the position information of the alignment data and the position information of the previous alignment data of the alignment data comprises:
the transmitting node judges whether the position information of the comparison data is an actual position or a relative position according to the position information identification of the comparison data aiming at each comparison data;
the transmitting node determines the position information of the comparison data as the actual position of the photon corresponding to the comparison data if judging that the position information of the comparison data is the actual position aiming at each comparison data;
and the transmitting node calculates the actual position of the photon corresponding to the comparison data according to the position information of the comparison data and the actual position of the photon corresponding to the previous comparison data of the comparison data if judging that the position information of the comparison data is the relative position aiming at each comparison data.
7. A node, wherein the node is a receiving node in a quantum key distribution system, comprising:
the receiving unit is used for receiving the photon sequence sent by the transmitting node, randomly selecting one basic vector from multiple preset basic vectors as a decoding basic vector of the photon aiming at each received photon, and measuring the photon by using the decoding basic vector of the photon to obtain the quantum state of the photon; wherein the sequence of photons comprises a plurality of photons encoded by the transmitting node;
a calculating unit, configured to calculate, for each received photon, a relative position of the photon according to an actual position of the photon in the photon sequence and an actual position of a previously received photon in the photon sequence; wherein, if the photon is the first received photon, the actual position of the previous received photon in the photon sequence refers to a preset synchronous optical position;
a determining unit, configured to determine, for each received photon, an actual position or a relative position of the photon as position information of the photon; wherein the relative position of at least one of the photons is determined as the position information of the photon;
the transmitting unit is used for feeding back comparison data of each photon to the transmitting node; the comparison data of each photon comprises position information of the photon, a position information identifier for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon, and a decoding basis vector of the photon;
the generating unit is used for generating a second key according to the quantum state of the correct photon measured in the photon sequence; the photon with correct measurement refers to a photon with the coding basis vector and the decoding basis vector which correspond to each other and are the same basis vector, and the coding basis vector of the photon refers to a basis vector used when the emission node codes the photon.
8. The node according to claim 7, wherein the determining unit comprises:
the judging unit is used for judging whether the absolute value of the relative position of the photon is larger than a preset threshold value or not aiming at each received photon;
a determining subunit, configured to determine, for each received photon, if an absolute value of a relative position of the photon is greater than the threshold, an actual position of the photon as position information of the photon;
and if the absolute value of the relative position of the photon is less than or equal to the threshold, determining the relative position of the photon as the position information of the photon.
9. A node, wherein the node is a transmitting node in a quantum key distribution system, comprising:
a transmitting unit for transmitting the photon sequence to a receiving node; the photon sequence comprises a plurality of photons, the quantum state of each photon is encoded by the emitting node by using the encoding basis vector of the photon, and the encoding basis vector of the photon is any one of the basis vectors randomly selected from a plurality of preset basis vectors by the emitting node;
a receiving unit, configured to receive a plurality of comparison data from the receiving node; each piece of comparison data corresponds to a photon, and the comparison data comprises position information of the corresponding photon, position information identification of the photon and decoding basis vector of the photon; wherein the position information identification of the photon is used for indicating that the position information of the photon is the actual position of the photon or the relative position of the photon; a decoded basis vector of the photon, referring to a basis vector used by the receiving node when measuring the photon;
a determining unit, configured to determine, for each piece of comparison data, an actual position of a photon corresponding to the comparison data in the photon sequence according to position information of the comparison data and position information of a previous comparison data of the comparison data, so as to determine the photon corresponding to the comparison data;
the comparison unit is used for comparing the decoding basis vector of the photon with the coding basis vector of the photon aiming at the photon corresponding to each comparison data, so as to determine the photon with correct measurement in the photon sequence; wherein the photons with correct measurement refer to the photons with the corresponding encoding basis vectors consistent with the decoding basis vectors;
and the generating unit is used for generating a first key according to the quantum state of the correct photon measured in the photon sequence.
10. The node according to claim 9, wherein the determining unit comprises:
the judging unit is used for judging whether the position information of the comparison data is an actual position or a relative position according to the position information identification of the comparison data aiming at each comparison data;
the determining subunit is configured to determine, for each piece of comparison data, if it is determined that the position information of the comparison data is an actual position, the position information of the comparison data as an actual position of a photon corresponding to the comparison data;
and the calculating unit is used for calculating the actual position of the photon corresponding to the comparison data according to the position information of the comparison data and the actual position of the photon corresponding to the previous comparison data of the comparison data if the position information of the comparison data is judged to be the relative position according to each comparison data.
CN201911419496.5A 2019-12-31 2019-12-31 Quantum key distribution method and node Active CN113132093B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201911419496.5A CN113132093B (en) 2019-12-31 2019-12-31 Quantum key distribution method and node

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201911419496.5A CN113132093B (en) 2019-12-31 2019-12-31 Quantum key distribution method and node

Publications (2)

Publication Number Publication Date
CN113132093A CN113132093A (en) 2021-07-16
CN113132093B true CN113132093B (en) 2022-04-08

Family

ID=76769560

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201911419496.5A Active CN113132093B (en) 2019-12-31 2019-12-31 Quantum key distribution method and node

Country Status (1)

Country Link
CN (1) CN113132093B (en)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114143860A (en) * 2021-11-10 2022-03-04 清华大学 Quantum direct communication method and device, message sending end and message receiving end

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106850073A (en) * 2017-01-17 2017-06-13 浙江神州量子网络科技有限公司 User terminal, MDI QKD systems and method and network system in quantum key distribution system
CN108206716A (en) * 2016-12-20 2018-06-26 科大国盾量子技术股份有限公司 Synchronous method and device and dissemination system applied to quantum key distribution system
CN108737074A (en) * 2017-04-13 2018-11-02 科大国盾量子技术股份有限公司 A kind of information synchronization method and device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4173422B2 (en) * 2002-12-04 2008-10-29 日本電信電話株式会社 Quantum key distribution method and quantum key distribution system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108206716A (en) * 2016-12-20 2018-06-26 科大国盾量子技术股份有限公司 Synchronous method and device and dissemination system applied to quantum key distribution system
CN106850073A (en) * 2017-01-17 2017-06-13 浙江神州量子网络科技有限公司 User terminal, MDI QKD systems and method and network system in quantum key distribution system
CN108737074A (en) * 2017-04-13 2018-11-02 科大国盾量子技术股份有限公司 A kind of information synchronization method and device

Also Published As

Publication number Publication date
CN113132093A (en) 2021-07-16

Similar Documents

Publication Publication Date Title
CN105553649B (en) Method and apparatus for generating secret key
CN103460639B (en) For guaranteeing the system and method for secure wireless communication
JP4995967B2 (en) Communication of identifiers for peer discovery in peer-to-peer networks
JP5221653B2 (en) Communication of identifiers for peer discovery in peer-to-peer networks
CN101790852B (en) In a peer-to-peer network for the transmission of the identifier of peer discovery
US7986783B2 (en) Data transmitting apparatus
Yang et al. Quantum secure direct communication with entanglement source and single-photon measurement
CN101057436B (en) Data transmitting apparatus
US8401193B2 (en) System and method for securing wireless communications
CN101207628A (en) Method and system for managing shared information
Rezki et al. Ergodic secret message capacity of the wiretap channel with finite-rate feedback
CN113141252A (en) Quantum key distribution method, quantum communication method, device and system
CN113132093B (en) Quantum key distribution method and node
CN105049198A (en) Asymmetry-based communication method of decoy-state quantum key distribution protocols
CN105407483A (en) Method for safe aggregation model communication based on public-state key in wireless sensor network
CN113055170A (en) Method for implementing continuous variable quantum secret sharing of autonomously selectable users, electronic device and computer-readable storage medium
US7260222B2 (en) Shared data refining device and shared data refining method
KR101055843B1 (en) Method for encryption and decryption of transaction in power network and system thereof
US20100158249A1 (en) Data transmitting apparatus and data receiving apparatus
WO2011103800A1 (en) System and method for securing wireless transmissions
JP4879294B2 (en) Quantum cryptographic communication data processing method and quantum cryptographic communication device
CN109921903B (en) System, method and device for detecting quantum key code rate authenticity
RU2585992C2 (en) System and method for wireless communication
Haghighat et al. Relay pre-selection for reducing CSI transmission in wireless sensor networks
US7606367B2 (en) Quantum cryptography with fewer random numbers

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant