CN113572597B - Single-state half-quantum key distribution system and method - Google Patents
Single-state half-quantum key distribution system and method Download PDFInfo
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- CN113572597B CN113572597B CN202110266278.3A CN202110266278A CN113572597B CN 113572597 B CN113572597 B CN 113572597B CN 202110266278 A CN202110266278 A CN 202110266278A CN 113572597 B CN113572597 B CN 113572597B
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Abstract
The application provides a system and a method for distributing a singlet half quantum key, wherein the system comprises a transmitting end and a receiving end, the transmitting end comprises a signal light unit, an optical transmission unit, a phase modulator unit and a detector unit, the signal light unit, the optical transmission unit and the phase modulator unit are sequentially connected, the detector unit is connected with the phase modulator unit and the optical transmission unit, and the phase modulator unit is an unequal arm interferometer; the receiving end comprises an intensity modulator unit, the intensity modulator unit is connected with the phase modulator unit, and the intensity modulator unit is an interference loop; the interference loop is used for loading voltage to the received light pulse group sent by the unequal arm interferometer, obtaining a processed light pulse group, and sending the processed light pulse group to the unequal arm interferometer. The system and the method adopt a selective modulation mode to realize a singlet half quantum key distribution protocol, solve the problem of unreasonable design of the existing system, and have extremely high safety and practical application feasibility.
Description
Technical Field
The application relates to the field of quantum secret communication, in particular to a system and a method for distributing a singlet half-quantum key.
Background
Currently, with the use of computers and the internet in the communication field, the encryption requirement for communication data is gradually increasing. In the data encryption means, some encryption means depending on the complexity of calculation still have certain possibility of being deciphered, while the quantum cryptography is based on the hessian-based inaccurate measurement principle and the unknown quantum state unclonable principle, so that the requirements of a one-time-pad encryption system can be theoretically met, and the method has theoretical unconditional security.
In 1984, bennett and Brassard proposed a first quantum key distribution protocol, after which both parties to the quantum key distribution protocol were often defined as Alice and Bob ends, both having the ability to manipulate quanta, e.g. to complete the preparation and measurement of qubits on an arbitrary basis. Until 2007, boyer et al proposed the concept of a half-quantum key distribution protocol and a four-state protocol based on the previous quantum key distribution protocol, which reduced the requirements of the quantum key distribution protocol, and the Bob end only needed to possess the ability to prepare the quantum state of the Z-base form and directly transfer the quantum bits.
In 2009, zou et al proposed a singlet half quantum key distribution protocol for half quantum key distribution, and the specific step flow of the protocol is as follows: and preparing a photon with the quantum state of |++ > at the Alice end, sending the photon to the Bob end, randomly selecting the 'resending photon after measuring by using the Z base' or the 'returning photon without any operation', randomly selecting the Z base or the X base by the photon sent back by the Bob end by the Alice end to measure, and finally simultaneously disclosing the operation selection by Alice and the Bob, wherein if the Z base is selected by the Bob end and the Z base is also selected by the Alice end, the quantum bit at the position can be used as a code, and if the returning photon without any operation is selected by the Bob end and the X base is selected by the Alice end, the quantum bit at the position can be used for detecting eavesdropping.
In the current implementation method, as the implementation method of the singlet half quantum key distribution has a certain defect in design, a receiving end is required to regenerate new photons according to the result obtained by measuring photons and send the new photons to a sending end, the operation is complex, and potential safety hazards of information leakage caused by marking attack exist, so that the current implementation method is not safe enough and is difficult to have practical application feasibility.
Disclosure of Invention
The embodiment of the application aims to provide a singlet half-quantum key distribution system and a method, which adopt a selective modulation mode to realize a singlet half-quantum key distribution protocol, solve the problem of unreasonable design of a protocol system in the prior art, simplify the operation of a receiving end, realize a stable singlet half-quantum key distribution protocol double-path experiment system and have extremely high safety and practical application feasibility.
In a first aspect, an embodiment of the present application provides a singlet half quantum key distribution system, including a transmitting end and a receiving end, where the transmitting end includes a signal light unit, an optical transmission unit, a phase modulator unit, and a detector unit, where the signal light unit, the optical transmission unit, and the phase modulator unit are sequentially connected, and the detector unit is connected with the phase modulator unit and the optical transmission unit, and the phase modulator unit is an anisometric arm interferometer;
the receiving end comprises an intensity modulator unit, the intensity modulator unit is connected with the unequal arm interferometer, and the intensity modulator unit is an interference loop;
the interference loop is used for loading voltage to the received light pulse group sent by the unequal arm interferometer, obtaining a processed light pulse group, and sending the processed light pulse group to the unequal arm interferometer.
In the implementation process, the singlet half quantum key distribution system of the embodiment of the application adopts the interference loop as the intensity modulator unit of the receiving end and is matched with the anisometric arm interferometer as the phase modulator unit, so that the system is more reasonable in receiving end design compared with the prior art, can realize the singlet half quantum key distribution protocol in a selective modulation mode, solves the problem of unreasonable design of the protocol system of the prior art, and has extremely high safety and practical application feasibility.
Further, the interference loop comprises a polarization beam splitter and an intensity modulator, wherein the polarization beam splitter is connected with the unequal arm interferometer through a quantum channel, and two ends of the intensity modulator are respectively connected with the polarization beam splitter.
In the implementation process, the interference loop of the combination of the polarization beam splitter and the intensity modulator is adopted, so that the operation of a receiving end on a transmitted light pulse group in the single-state half-quantum key distribution protocol can be effectively realized, the single-state half-quantum key distribution protocol is realized by adopting a selective modulation mode, the problem of unreasonable design of a protocol system in the prior art is solved, and the operation of the receiving end is simplified.
Further, the anisometric arm interferometer comprises a first beam splitter, a second beam splitter, a short arm subunit and a long arm subunit;
the first beam splitter is connected with the optical transmission unit, the first beam splitter is respectively connected with the long arm subunit and the short arm subunit, the long arm subunit and the short arm subunit are respectively connected with the second beam splitter, and the second beam splitter is connected with the interference loop through a quantum channel.
In the implementation process, the non-equal arm interferometer comprises a long-arm subunit and a short-arm subunit, and because the non-equal arm interferometer comprises the two subunits with different lengths, the optical paths of the two subunits are different, and therefore under the cooperation of the first beam splitter, an optical pulse signal received by the non-equal arm interferometer from the optical transmission unit can be emitted into two optical pulses in front of and behind, and the preparation operation needed by a sending end in a single-state half quantum key distribution protocol is realized.
Further, the long arm subunit includes a second polarizer and an optical fiber attenuator connected, the second polarizer is connected with the first beam splitter, and the optical fiber attenuator is connected with the second beam splitter;
the short arm subunit includes a phase modulator and a first polarizer connected, the phase modulator being connected to the first beam splitter, the first polarizer being connected to the second beam splitter.
In the implementation process, one of the functions of the unequal arm interferometer is to realize the preparation of the optical pulse group through the different optical path lengths of the short arm subunit, wherein the short arm subunit comprises a phase modulator, the phase of the optical pulse incident to the short arm subunit can be loaded, and the long arm subunit comprises an optical fiber attenuator, so that the intensity loss of the optical pulse of the long arm subunit can be adjusted, the optical pulse of the long arm subunit and the optical pulse of the short arm subunit have the same intensity, and the modules of the long arm subunit and the short arm subunit form the supplement and perfect preparation problem of the optical pulse group.
Further, the signal light unit comprises a laser, an optical isolator and an optical attenuator which are sequentially connected, and the optical attenuator is connected with the optical transmission unit.
In the implementation process, the combination of the laser, the optical isolator and the optical attenuator is adopted, and the signal light unit can generate stable signal light and adjust the signal light to be at proper intensity, so that a stable and proper signal light foundation is provided for the operation of the subsequent unit.
Further, the optical transmission unit comprises an optical circulator connected with the signal light unit and the unequal arm interferometer.
In the implementation process, the optical circulator in the optical transmission unit can effectively transmit the signal light between the signal light unit and the non-equal arm interferometer.
Further, the detector unit comprises a first single photon detector and a second single photon detector, the first single photon detector is connected with the unequal arm interferometer, and the second single photon detector is connected with the light transmission unit.
In the implementation process, the detector unit is connected with the unequal arm interferometer and the optical transmission unit, so that two different optical pulse interference signal results can be obtained, and the content of the singlet half quantum key distribution protocol is reliably realized.
In a second aspect, an embodiment of the present application provides a method for distributing a singlet half quantum key, including:
the signal light unit generates light pulses and transmits the light pulses to the unequal arm interferometer through the light transmission unit;
the unequal arm interferometer processes the received light pulses to obtain a first pulse group, and sends the first pulse group to the interference loop;
the interference loop processes the received first pulse group to obtain a second pulse group, and sends the second pulse group to the unequal arm interferometer;
the unequal arm interferometer processes the received second pulse group to obtain a third pulse group, and sends the third pulse group to the optical transmission unit and the detector unit;
the detector unit receives a third pulse group and detects the third pulse group to obtain a detection result;
and the singlet half quantum key distribution system obtains a security key according to the detection result, the processing of the received light pulse by the unequal arm interferometer and the processing of the received first pulse group by the interference loop.
In the implementation process, the method for distributing the singlet half quantum key adopts the interference loop as the intensity modulator unit of the receiving end and is matched with the anisometric arm interferometer serving as the phase modulator unit, compared with the prior art, the method can realize the singlet half quantum key distribution protocol in a selective modulation mode, simplifies the operation of the receiving end and has extremely high safety and practical application feasibility.
Further, the anisometric arm interferometer processes the received light pulses to obtain a first set of pulses comprising:
the received signal pulses are separated into first and second light pulses by a difference in length of the long and short arm subunits in the anisometric arm interferometer, the first and second light pulses comprising the first set of pulses.
In the implementation process, the optical path difference value of the long and short arm subunits in the anisometric interferometer is utilized, so that the process of preparing and sending preset quantum states by the sending end in the singlet half quantum key distribution protocol can be better realized.
Further, the interference loop processes the received first pulse group to obtain a second pulse group, including:
the interference loop takes the received first pulse group as the second pulse group;
or, the interference loop performs voltage interference operation on the first pulse of the first pulse group to obtain the second pulse group;
or, the interference loop performs voltage interference operation on the second pulse of the first pulse group to obtain the second pulse group.
In the implementation process, the interference loop is adopted as the receiving end, so that the modulation operation of the receiving end on the optical pulse sent by the sending end is realized, the single-state half-quantum key distribution protocol can be realized in a selective modulation mode, the problem of unreasonable design of a protocol system in the prior art is reasonably solved, the operation of the receiving end is simplified, and the stable double-path experimental system of the single-state half-quantum key distribution protocol is realized.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a singlet half quantum key distribution system according to a first embodiment of the present application;
fig. 2 is a schematic structural diagram of a signal light unit according to an embodiment of the present disclosure;
fig. 3 is a schematic structural diagram of a phase modulator unit according to a first embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of an intensity modulator unit according to a first embodiment of the present disclosure;
fig. 5 is a flow chart of a method for distributing a singlet half quantum key according to a second embodiment of the present application.
Detailed Description
The following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.
In the present application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are used primarily to better describe the present application and its embodiments and are not intended to limit the indicated device, element or component to a particular orientation or to be constructed and operated in a particular orientation.
Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate.
Furthermore, the terms "mounted," "configured," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or a point connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish between different devices, elements, or components (the particular species and configurations may be the same or different), and are not used to indicate or imply the relative importance and number of devices, elements, or components indicated. Unless otherwise indicated, the meaning of "a plurality" is two or more.
Example 1
Referring to fig. 1, fig. 1 is a block diagram of a singlet half quantum key distribution system according to an embodiment of the present application.
The singlet half quantum key distribution system comprises a transmitting end and a receiving end, wherein the transmitting end comprises a signal light unit 1, an optical transmission unit 2, a phase modulator unit 3 and a detector unit 4, the signal light unit 1, the optical transmission unit 2 and the phase modulator unit 3 are sequentially connected, the phase modulator unit 3 is connected with the receiving end, the detector unit 4 is connected with the phase modulator unit 3 and the optical transmission unit 2, and the phase modulator unit 4 is an unequal arm interferometer;
the receiving end comprises an intensity modulator unit 5, the intensity modulator unit 5 is connected with the non-equal arm interferometer, and the intensity modulator unit 5 is an interference loop;
the interference loop is used for loading voltage to the received light pulse group sent by the unequal arm interferometer, obtaining a processed light pulse group, and sending the processed light pulse group to the unequal arm interferometer.
In the present embodiment, the signal light unit 1 can provide a stable signal light output; the optical transmission unit 2 is used for effectively transmitting the signal light between the signal light unit and the unequal arm interferometer; the non-equal arm interferometer can realize the encoding process of time phase in the singlet half quantum key distribution protocol; the detector unit 4 can detect and obtain the interference result of the signal light pulse; the interference loop is used for selecting and operating the light pulse in the realization of the singlet half quantum key distribution protocol.
The sending end can also be called as an Alice sending end or an Alice end, and the receiving end can also be called as a Bob receiving end or a Bob end; the singlet half quantum key distribution system has a bidirectional channel, and channels along a signal light unit 1, an optical transmission unit 2, an unequal arm interferometer and an interference loop are channels sent from a sending end to a receiving end and are forward channels; the channels along the interference loop, the anisometric arm interferometer, the optical transmission unit 2 and the detector unit 4 are the channels sent from the receiving end to the transmitting end, and are the back channels.
The interference loop processes the voltage applied to the received optical pulse group, and one option is to directly send the optical pulse group to the unequal arm interferometer through the interference loop without applying the voltage to the optical pulse group, and the option can be defined as CTRL operation of the receiving end; another option is to apply a voltage to the optical pulse group and send the optical pulse group after the voltage application to the anisometric arm interferometer, which can be defined as SIFT operation at the receiving end.
The SIFT operation of the receiving end is realized through the interference loop, so that new light pulses can be transmitted to the transmitting end without being manufactured by the receiving end, the original light pulses subjected to voltage loading treatment are transmitted to the transmitting end, the operation is simplified, meanwhile, the problem of information leakage caused by marking attack in the process of manufacturing the new light pulses can be avoided, and the safety of the system and the feasibility of practical application are improved.
Optionally, the non-equal arm interferometer may be a non-equal arm mach-zehnder interferometer, and the interference loop may be a sagnac interference loop.
According to the singlet half quantum key distribution system, the interference loop is adopted as the intensity modulator unit of the receiving end, and is matched with the unequal arm interferometer serving as the phase modulator unit, so that the system is more reasonable in receiving end design compared with the prior art, the singlet half quantum key distribution protocol can be realized in a selective modulation mode, the problem that the design of a protocol system in the prior art is unreasonable is solved, and the system has extremely high safety and practical application feasibility.
Referring to fig. 1 and 2, fig. 2 is a schematic structural diagram of a signal light unit of the present application, where the signal light unit 1 includes a laser 101, an optical isolator 102, and an optical attenuator 103, and the laser 101, the optical isolator 102, and the optical attenuator 103 are sequentially connected.
Wherein the laser 101 is used for generating stable signal light; the optical isolator 102 is used for preventing backward transmission light generated in the optical path from generating adverse effects on the light source and the optical path system, namely isolating the backward transmission light and avoiding interference of the backward transmission light; the optical attenuator 103 is used to adjust the output signal light to a suitable intensity, where a suitable intensity means that the light intensity is within a threshold of the detector when the signal light finally reaches the detector of the detector unit.
Referring to fig. 1, the optical transmission unit 2 comprises an optical circulator, wherein the optical circulator has three ports, a first port of the optical circulator is connected to the optical attenuator 103, a second port of the optical circulator is connected to the phase modulator unit 3, and a third port of the optical circulator is connected to the detector unit 4;
the optical circulator functions to transmit signal light as an optical pulse to the phase modulator unit 3 connected to the second port and transmit an optical pulse returned from the phase modulator unit 3 to the detector unit 4 connected to the third port upon receiving the signal light generated by the signal light unit 1.
Referring to fig. 1 and 3, where fig. 3 is a schematic diagram of a phase modulator unit of the present application, and phase modulator unit 3 is a non-equal arm interferometer, where the non-equal arm interferometer includes a first beam splitter 105, a second beam splitter 110, a long arm subunit, and a short arm subunit, and the first beam splitter 105 has four ports, where a first port of the first beam splitter 105 is connected to a second port of the optical circulator, a second port of the first beam splitter 105 is connected to one end of the long arm subunit, a third port of the first beam splitter 105 is connected to one end of the short arm subunit, and a fourth port of the first beam splitter 105 is connected to the detector unit 4; the second beam splitter 110 has three ports, the other end of the long arm subunit is connected to the first port of the second beam splitter 110, the other end of the short arm subunit is connected to the second port of the second beam splitter 110, and the third port of the second beam splitter 110 is connected to the interference loop of the receiving end through a quantum channel.
The first beam splitter 105 is configured to split the received light pulse into a first light pulse and a second light pulse, and to output the first light pulse from the second port and the third port of the first beam splitter 105 to the long-arm subunit and the short-arm subunit.
In this embodiment, the short-arm subunit comprises a phase modulator 106 and a first polarizer 107 connected, where the phase modulator 106 is connected to the third port of the first beam splitter 105, the first polarizer 107 is connected to the second port of the second beam splitter 110, and the phase modulator 106 is configured to load the phase of the received optical pulse; the function of the first polarizer 107 is to adjust the polarization mode of the returned light pulse to reach maximum output power when the light pulse is incident on the phase modulator 106 when the short arm subunit receives the light pulse returned from the second beam splitter 110 in the back channel.
In this embodiment, the long-arm subunit includes a second polarizer 108 and an optical fiber attenuator 109 that are connected, where the second polarizer 108 is connected to the second port of the first beam splitter 105, the optical fiber attenuator 109 is connected to the first port of the second beam splitter 110, and the function of the second polarizer 108 is to adjust, in a back channel, when the long-arm subunit receives an optical pulse returned from the optical fiber attenuator 109, the polarization mode of the returned optical pulse, so that when the optical pulse is incident on the first beam splitter 105, a preset interference contrast can be achieved; the function of the fiber attenuator 109 is to adjust the loss of the light pulses in the long arm subunit so that the light pulses in the long arm subunit have the same intensity as the light pulses in the short arm subunit.
The second beam splitter can emit the first light pulse and the second light pulse from the third port, and send the first light pulse and the second light pulse to the interference loop through the quantum channel, and the first light pulse and the second light pulse can be emitted from the port in tandem due to the arm length difference of the long-arm subunit and the short-arm subunit, so that the first light pulse and the second light pulse can be considered to be combined to obtain the first pulse group.
In this embodiment, when the phase modulator 106 does not apply a phase voltage to the optical pulse, then the Z-basis vector in the time-phase code corresponds to the X-basis vector in the time-phase code when the phase modulator selects to apply two voltages, namely 0 or vpi, to the optical pulse; where V pi is the half-wave voltage of the phase modulator.
Alternatively, the phase modulator 106 may load the optical pulse with a phase of 0 or pi.
Optionally, first beam splitter 105 and second beam splitter 110 each have a splitting ratio of 1:1.
Referring to fig. 1, the detector unit 4 includes a first single photon detector 111 and a second single photon detector 112, the first single photon detector 111 being connected to a third port of the optical circulator, the second single photon detector 112 being connected to a fourth port of the first beam splitter 105.
Referring to fig. 1 and fig. 4, fig. 4 is a schematic structural diagram of an intensity modulator unit of the present application, and the intensity modulator unit 5 is an interference loop, including a polarization beam splitter 201 and an intensity modulator 202, where the polarization beam splitter 201 is connected to the second beam splitter 202 through a quantum channel, and two ends of the intensity modulator 202 are respectively connected to the polarization beam splitter 201.
Wherein the intensity modulator 202 is configured to generate a selection of equal probabilities, to choose whether to modulate the received first pulse group of applied voltages, and if not, the intensity modulator 202 is not operated to send the first pulse group back to the second beam splitter 110 via the polarizing beam splitter 201 in the original order, and if selected to modulate, to generate a new selection of equal probabilities, to reduce the intensity of the first or second light pulses to 0, i.e. to randomly reserve one light pulse of the first pulse group, and finally to send the reserved light pulse as a second pulse group to the second beam splitter 110 via the polarizing beam splitter 201.
Optionally, the intensity modulator 202 and the polarization beam splitter 201 are connected by polarization maintaining fibers, and the lengths of the polarization maintaining fibers connected should be the same.
Optionally, in the singlet half quantum key distribution system according to the embodiments of the present application, a connection manner adopted by each unit may be optical fiber connection, where an optical fiber may be a single-mode optical fiber.
In the singlet half quantum key distribution system in the embodiment of the present application, the process of determining the key refers to the related content of the singlet half quantum key distribution method described below, and no further description is given here.
Example two
Referring to fig. 1 and fig. 5, fig. 5 is a schematic flow chart of a method for distributing a singlet half quantum key according to an embodiment of the present application, where the method for distributing a singlet half quantum key according to the embodiment of the present application includes:
step S110, the signal light unit 1 generates light pulse and transmits the light pulse to the non-equal arm interferometer through the light transmission unit 2;
step S120, the unequal arm interferometer processes the received light pulse to obtain a first pulse group, and sends the first pulse group to the interference loop;
step S130, the interference loop processes the received first pulse group to obtain a second pulse group, and sends the second pulse group to the unequal arm interferometer;
step S140, the non-equal arm interferometer processes the received second pulse group to obtain a third pulse group, and sends the third pulse group to the optical transmission unit 2 and the detector unit 4;
step S150, the detector unit 4 receives the third pulse group and detects the third pulse group to obtain a detection result;
in step S160, the singlet half quantum key distribution system obtains the security key according to the detection result, the processing of the received light pulse by the anisometric interferometer, and the processing of the received first pulse group by the interference loop.
According to the method for distributing the singlet half quantum key, the interference loop is adopted as the intensity modulator unit of the receiving end, and the interference loop is matched with the anisometric arm interferometer serving as the phase modulator unit.
As an optional implementation manner, step S120, the interference loop processes the received first pulse set to obtain a second pulse set, which may include:
the received signal pulses are divided into first and second light pulses by the difference in length between the long and short arm subunits in the anisometric arm interferometer, the first and second light pulses forming a first pulse group.
Wherein when the first pulse set exits the third port of the second beam splitter 110 of the non-equal arm interferometer, no phase difference should exist, at this time, the first pulse group can correspond to time the +++ state of the phase-encoded X-basis vector, phase encoded X basis vector in the +++ state.
As an optional implementation, step S130, the interference loop processes the received first pulse group to obtain a second pulse group, which may include:
step S131, the interference loop takes the received first pulse group as a second pulse group;
or, step S132, the interference loop performs voltage interference operation on the first pulse of the first pulse group to obtain a second pulse group;
or, in step S133, the interference loop performs a voltage intervention operation on the second pulse of the first pulse group, to obtain the second pulse group.
Step S131 may be defined as a CTRL operation of interference loop selection, step S132 and step S133 may be defined as a SIFT operation of interference loop selection, in which the voltage intervening operation may reduce the intensity of the selected light pulse in the first pulse group to 0, and the resulting second pulse group may also have different definitions according to the selected light pulse, if the operation performed by the interference loop is the CTRL operation, the returned second pulse group may be a |++ > state of time phase coding, and if the operation performed by the interference loop is the SIFT operation, the |0> state or the |1> state of corresponding time phase coding may be defined according to a preset rule, for example: the second pulse group obtained by the operation corresponding to the step S132 in the SIFT operation corresponds to the |0> state of the time phase code; the second pulse group obtained in the SIFT operation corresponding to the operation of step S133 corresponds to the |1> state of the time phase code.
When the anisometric arm interferometer receives the second pulse group, the second pulse group input to the second beam splitter 110 will split the second pulse group first, and the second pulse group beam split into the short arm subunit will receive a random selection of the phase modulator, and select whether to apply a voltage to perform a phase modulation of 0 or pi, and the second pulse group beam split into the long arm subunit will perform an intensity adjustment.
If the operation performed by the interference loop is CTRL operation, the first light pulse and the second light pulse exist in the second pulse group, and since the difference between the first two pulses is generated based on the arm length difference between the short arm subunit and the long arm subunit, when the second pulse group passes through the short arm subunit and the long arm subunit and is combined by the first beam splitter 105, the beam splitting of the second light pulse passing through the short arm subunit interferes with the beam splitting of the first light pulse passing through the long arm subunit, so as to obtain three light pulses on three equidistant time slots, namely, the third pulse group.
If the operation performed by the interference loop is SIFT operation, the second pulse group here has only the first or second light pulse, and the light pulses are combined by the first beam splitter 105 to obtain three light pulses on three equidistant time slots, namely, the third pulse group, and the three light pulses include one null pulse. If the SIFT operation performed by the interference loop reduces the light intensity of the first previous pulse to 0, namely the null pulse, the first pulse in the third pulse group is the null pulse, and if the SIFT operation performed by the receiving end of the interference loop reduces the light intensity of the second subsequent pulse to 0, namely the null pulse, the third pulse in the third pulse group is the null pulse.
If the interference loop carries out CTRL operation, the result detected by the detector unit is different according to the phase modulation of the second pulse group by the phase modulator; for example, in the case that the phase modulator is loaded with phase 0, when the third pulse group reaches the first single photon detector 111, the first single photon detector 111 may obtain a single photon count corresponding to the interference constructive pattern at a preset time slot position, and when the third pulse group reaches the second single photon detector 112, the second single photon detector 112 may obtain a single photon count corresponding to the interference destructive pattern at a preset time slot position; and if the phase modulator is loaded with the phase pi, the result is opposite, the first single photon detector 111 can obtain the single photon count corresponding to the interference cancellation pattern at the preset time slot position, and the second single photon detector 112 can obtain the single photon count corresponding to the interference constructive pattern at the preset time slot position, where the single photon counts at two positions are the detection results obtained by the detector units.
The three equidistant time slots from front to back are set as t00, t01 and t02, if the operation of the interference loop is CTRL operation, the preset time slot is the t01 position, the single photon count corresponding to interference can be obtained, and if the operation of the interference loop is SIFT operation, only one light pulse exists at the t01 position, and no interference occurs.
After the detection result is obtained, the sending end can judge the selection of the intensity modulation of the receiving end, namely the interference loop, through the counting on different time slots, and the selection of the loading phase voltage corresponding to the sending end is transmitted to the receiving end through a public channel.
The acquired detection result, the processing of the received light pulse by the non-equal arm interferometer and the processing of the received first pulse group by the interference loop are judged by the singlet half-quantum key distribution system according to the singlet half-quantum key distribution protocol, and the method specifically comprises the following steps:
when the interference loop processes the received first pulse group into the SIFT operation, if the transmitting end adopts the Z-base vector measurement, that is, the first single photon detector and the second single photon detector detect the empty pulse at the t00 position or the t02 position of the time slot, the code can be formed according to the measurement result, wherein: if the SIFT operation and measurement result of the interference loop is in the state of |0>, then code 0 can be formed; if the SIFT operation and measurement of the interferometric loop is in the |1> state, then code 1 can be formed.
When the interference loop processes the received first pulse group into SIFT operation, if the transmitting end adopts X-base vector measurement, the bit code is abandoned no matter the measurement result is in the I+ state or the I- -.
When the interference loop processes the received first pulse group to be CTRL operation, if the transmitting end adopts X-base vector measurement, that is, the interference constructive and destructive phenomena of the preset position of the time slot are detected through the first single photon detector and the second single photon detector, whether the system is eavesdropped or not can be monitored according to the measurement result, and if the transmitting end adopts Z-base vector measurement, the bit code is abandoned.
The rest of the content of the singlet half quantum key distribution system in the embodiment of the present application may refer to the specific content of the first embodiment, and will not be described herein.
In all the embodiments, the terms "large" and "small" are relative terms, "more" and "less" are relative terms, "upper" and "lower" are relative terms, and the description of such relative terms is not repeated herein.
It should be appreciated that reference throughout this specification to "in this embodiment," "in an embodiment of the application," or "as an alternative" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. Thus, the appearances of the phrases "in this embodiment," "in this application embodiment," or "as an alternative embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Those skilled in the art will also appreciate that the embodiments described in the specification are all alternative embodiments and that the acts and modules referred to are not necessarily required in the present application.
In various embodiments of the present application, it should be understood that the size of the sequence numbers of the above processes does not mean that the execution sequence of the processes is necessarily sequential, and the execution sequence of the processes should be determined by the functions and internal logic thereof, and should not constitute any limitation on the implementation process of the embodiments of the present application.
The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present application, and the changes and substitutions are intended to be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A singlet half quantum key distribution system is characterized by comprising a transmitting end and a receiving end,
the transmitting end comprises a signal light unit, an optical transmission unit, a phase modulator unit and a detector unit, wherein the signal light unit, the optical transmission unit and the phase modulator unit are sequentially connected, the detector unit is connected with the phase modulator unit and the optical transmission unit, and the phase modulator unit is an unequal arm interferometer;
the receiving end comprises an intensity modulator unit, the intensity modulator unit is connected with the unequal arm interferometer, and the intensity modulator unit is an interference loop;
the interference loop is used for loading voltage to the received light pulse group sent by the unequal arm interferometer, obtaining a processed light pulse group, and sending the processed light pulse group to the unequal arm interferometer.
2. The singlet half quantum key distribution system of claim 1 wherein the first quantum key distribution system comprises a first quantum key,
the interference loop comprises a polarization beam splitter and an intensity modulator, wherein the polarization beam splitter is connected with the unequal arm interferometer through a quantum channel, and two ends of the intensity modulator are respectively connected with the polarization beam splitter.
3. The singlet half quantum key distribution system of claim 1 wherein the first quantum key distribution system comprises a first quantum key,
the anisometric arm interferometer includes a first beam splitter, a second beam splitter, a short arm subunit and a long arm subunit,
the first beam splitter is connected with the optical transmission unit, the first beam splitter is respectively connected with the long arm subunit and the short arm subunit, the long arm subunit and the short arm subunit are respectively connected with the second beam splitter, and the second beam splitter is connected with the interference loop through a quantum channel.
4. The singlet half quantum key distribution system according to claim 3 wherein,
the long-arm subunit comprises a second polarizer and an optical fiber attenuator which are connected, wherein the second polarizer is connected with the first beam splitter, and the optical fiber attenuator is connected with the second beam splitter;
the short arm subunit includes a phase modulator and a first polarizer connected, the phase modulator being connected to the first beam splitter, the first polarizer being connected to the second beam splitter.
5. The singlet half quantum key distribution system of claim 1 wherein the first quantum key distribution system comprises a first quantum key,
the signal light unit comprises a laser, an optical isolator and an optical attenuator which are sequentially connected, and the optical attenuator is connected with the optical transmission unit.
6. The singlet half quantum key distribution system of claim 1 wherein the first quantum key distribution system comprises a first quantum key,
the optical transmission unit comprises an optical circulator, and the optical circulator is connected with the signal optical unit and the unequal arm interferometer.
7. The singlet half quantum key distribution system of claim 1 wherein the first quantum key distribution system comprises a first quantum key,
the detector unit comprises a first single photon detector and a second single photon detector, wherein the first single photon detector is connected with the unequal arm interferometer, and the second single photon detector is connected with the optical transmission unit.
8. A method of singlet half quantum key distribution, characterized in that it is based on the singlet half quantum key distribution system according to any one of claims 1 to 7, the method comprising:
the signal light unit generates light pulses and transmits the light pulses to the unequal arm interferometer through the light transmission unit;
the unequal arm interferometer processes the received light pulses to obtain a first pulse group, and sends the first pulse group to the interference loop;
the interference loop processes the received first pulse group to obtain a second pulse group, and sends the second pulse group to the unequal arm interferometer;
the unequal arm interferometer processes the received second pulse group to obtain a third pulse group, and sends the third pulse group to the optical transmission unit and the detector unit;
the detector unit receives a third pulse group and detects the third pulse group to obtain a detection result;
and the singlet half quantum key distribution system obtains a security key according to the detection result, the processing of the received light pulse by the unequal arm interferometer and the processing of the received first pulse group by the interference loop.
9. The method of claim 8, wherein the non-equal arm interferometer processes the received light pulses to obtain a first set of pulses, comprising:
and dividing the received signal pulse into a first light pulse and a second light pulse by the length difference of a long arm subunit and a short arm subunit in the unequal arm interferometer, wherein the first light pulse and the second light pulse form the first pulse group.
10. The method of claim 8, wherein the interference loop processes the received first set of pulses to obtain a second set of pulses, comprising:
the interference loop takes the received first pulse group as the second pulse group;
or, the interference loop performs voltage interference operation on the first pulse of the first pulse group to obtain the second pulse group;
or, the interference loop performs voltage interference operation on the second pulse of the first pulse group to obtain the second pulse group.
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