CN112737775A - Transmitting end chip and method for discrete variable quantum key distribution - Google Patents

Transmitting end chip and method for discrete variable quantum key distribution Download PDF

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CN112737775A
CN112737775A CN202011591251.3A CN202011591251A CN112737775A CN 112737775 A CN112737775 A CN 112737775A CN 202011591251 A CN202011591251 A CN 202011591251A CN 112737775 A CN112737775 A CN 112737775A
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phase
light
modulator
phase modulator
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CN112737775B (en
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钱懿
胡晓
肖希
王磊
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Wuhan Research Institute of Posts and Telecommunications Co Ltd
Wuhan Optical Valley Information Optoelectronic Innovation Center Co Ltd
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Wuhan Research Institute of Posts and Telecommunications Co Ltd
Wuhan Optical Valley Information Optoelectronic Innovation Center Co Ltd
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    • 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
    • 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
    • H04L9/0819—Key transport or distribution, i.e. key establishment techniques where one party creates or otherwise obtains a secret value, and securely transfers it to the other(s)
    • 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
    • H04L9/0858—Details about key distillation or coding, e.g. reconciliation, error correction, privacy amplification, polarisation coding or phase coding

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Abstract

The invention discloses a transmitting end chip and a method for discrete variable quantum key distribution, and relates to the field of quantum key distribution. The transmitting end chip comprises a pulse laser, a first intensity modulator and a second intensity modulator which are connected in sequence; the first phase modulator and the second phase modulator are connected with the second intensity modulator; a first 1 x 2 beam splitter connected to the first phase modulator; a second 1 x 2 beam splitter connected to the second phase modulator; the delay waveguide and the first variable optical attenuator are connected with the first 1 multiplied by 2 beam splitter; the second variable optical attenuator and the third variable optical attenuator are connected with the second 1 multiplied by 2 beam splitter; a polarization rotation combiner connected with the first variable optical attenuator and the second variable optical attenuator, a 2 × 1 50 polarization rotation combiner connected with the delay waveguide and the third variable optical attenuator: 50 beam splitter. The invention can generate two quantum states of polarization state encoding DV-QKD and time-phase encoding DV-QKD, and only needs one design and production scheme.

Description

Transmitting end chip and method for discrete variable quantum key distribution
Technical Field
The invention relates to the field of quantum key distribution, in particular to a transmitting end chip and a method for discrete variable quantum key distribution.
Background
QKD (Quantum Key Distribution) is a technique for transmitting and establishing secret symmetric random numbers in a channel between two communicating parties by using the Quantum physical principle. The technology can be combined with the existing symmetric key encryption equipment to realize quantum secret communication. Among the QKD schemes, DV-QKD (Discrete Variable-Quantum Key Distribution) technology represented by the BB84 protocol is most widely used.
The binary quantum states of a typical single physical carrier can be represented by vectors on the sphere of a Bloch sphere (Bloch sphere) as shown in FIG. 1. The BB84 protocol needs a QKD transmitting end, and can accurately generate quantum states of 6 intersection points which correspond to the Bloch spherical surface and are respectively intersected with the Z axis, the X axis and the Y axis. Two points where the Z-axis and the sphere intersect are mapped in an actual physical system, and correspond to two mutually orthogonal states in a certain physical degree of freedom, such as a TE mode (transition electric mode) and a TM mode (transition Magnetic mode) in a Polarization (Polarization) state, or two non-overlapping Time-position (Time-Bin) modes of short pulses, and the corresponding DV-QKD implementations are respectively referred to as Polarization state coding and Time-Phase (Phase) coding.
However, the general polarization encoding DV-QKD has a large difference from the time-phase encoding DV-QKD in optical implementation, and the polarization encoding DV-QKD and the time-phase encoding DV-QKD of the reported integrated optical chip platform have different chip configurations. From a mass production perspective, two design and production schemes are generally required, resulting in higher design and production costs.
Disclosure of Invention
The purpose of the present application is to overcome the above-mentioned drawbacks of the background art, and to provide a transmitting end chip and a method for discrete variable quantum key distribution, which can generate two quantum states, namely, polarization state encoding DV-QKD and time-phase encoding DV-QKD, and only needs one design and production scheme, thereby effectively reducing the design and production costs.
In a first aspect, a transmitting-end chip for discrete variable quantum key distribution is provided, including:
the pulse laser, the first intensity modulator and the second intensity modulator are connected in sequence;
the first phase modulator and the second phase modulator are respectively connected with the second intensity modulator;
a first 1 x 2 beam splitter connected to the first phase modulator, a second 1 x 2 beam splitter connected to the second phase modulator;
the delay waveguide and the first variable optical attenuator are respectively connected with the first 1 multiplied by 2 beam splitter, and the second variable optical attenuator and the third variable optical attenuator are respectively connected with the second 1 multiplied by 2 beam splitter;
the polarization rotation synthesizer is respectively connected with the first variable optical attenuator and the second variable optical attenuator, and the output port of the polarization rotation synthesizer is used as a first external optical fiber coupling port of the transmitting end chip;
2 × 1 50 connected to the delay waveguide and the third variable optical attenuator, respectively: 50 beam splitter, the output port of which is used as the second external optical fiber coupling port of the transmitting end chip,
the transmitting end chip generates two quantum states of polarization state encoding DV-QKD and time-phase encoding DV-QKD.
In some embodiments, the pulse laser generates pulsed light with a period T, the first intensity modulator finely adjusts the light intensity of the pulsed light pulse by pulse, and the second intensity modulator outputs the input light to its two output ports at an adjustable ratio of light intensity distribution: a port A and a port B;
the first phase modulator increases the phase factor of the light field entering from the A port
Figure BDA0002868687620000031
Then, the output is output to the output port C of the device; the second phase modulator increases the phase factor of the light field entering from the port B
Figure BDA0002868687620000032
Then, the output is output to an output port D of the device;
the first 1 x 2 beam splitter outputs the light input from the port C to its two output ports at a pre-designed light intensity distribution ratio: ports E and F; the second 1 × 2 beam splitter outputs the optical power of the light input from the D port to its two output ports at a pre-designed light intensity distribution ratio: a port G and a port H;
the first variable optical attenuator attenuates the light input from the port F by an adjustable attenuation percentage and outputs the light to an output port I of the first variable optical attenuator; the second variable optical attenuator attenuates the light input from the G port by an adjustable attenuation percentage and outputs the light to an output port J of the second variable optical attenuator; the polarization rotation synthesizer outputs light input from the I port to a K port, namely a first external optical fiber coupling port, of an output port of the polarization rotation synthesizer, rotates the polarization direction of light input from the J port by 90 degrees and outputs the light to the K port, and light input from the I port and the J port respectively form TE mode energy components and TM mode energy components of the polarization state of the light output to the external optical fiber;
the delay waveguide prolongs the light propagation time from the port E to the port L of the output port of the delay waveguide according to a preset delay value relative to the light propagation time from the port H to the port M of the output port of the third variable optical attenuator; the third variable optical attenuator attenuates the light input to the port H by an adjustable attenuation percentage and outputs the light to the port M; 2 × 1 50: the 50 splitter couples half of the optical power input at the L port to a 2 x 1 50: and an output port N of the 50 beam splitters, namely a second external optical fiber coupling port N, and couples half of the optical power input by the port M to the port N.
In some embodiments, when the transmitting-end chip generates a polarization state physical degree of freedom quantum state, the K port and the N port are open and closed, and the internal devices required for generating different polarization state physical degree of freedom quantum states operate as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
producing physical freedom quantum states of polarization states
Figure BDA0002868687620000041
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000042
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000043
And satisfy
Figure BDA0002868687620000044
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000045
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000046
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000047
And satisfy
Figure BDA0002868687620000048
Producing objects in a polarisation stateQuantum state of physical degree of freedom
Figure BDA0002868687620000049
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000410
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200000411
And satisfy
Figure BDA00028686876200000412
Producing physical freedom quantum states of polarization states
Figure BDA00028686876200000413
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000414
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000051
And satisfy
Figure BDA0002868687620000052
In some embodiments, when the transmitting-end chip generates time-phase physical degree of freedom quantum states, the K port and the N port are closed and open, and the internal devices required for generating different time-phase physical degree of freedom quantum states operate as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000053
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000054
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000055
And satisfy
Figure BDA0002868687620000056
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000057
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000058
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000059
And satisfy
Figure BDA00028686876200000510
Generating time-phase physical degree of freedom quantum states
Figure BDA00028686876200000511
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000061
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000062
And satisfy
Figure BDA0002868687620000063
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000064
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000065
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000066
And satisfy
Figure BDA0002868687620000067
In some embodiments, the state switching frequency of the second intensity modulator is 1/T, and the phase change switching frequency of the first phase modulator and the second phase modulator is 1/T.
In some embodiments, the ratio of the light intensity of the light from port C to port E to the light intensity of the light from port C to port F is equal to the ratio of the light intensity of the light from port D to port H to the light intensity of the light from port D to port C.
In some embodiments, the optical power distribution ratio of the F-port to the E-port is close to or equal to the optical power distribution ratio of the G-port to the H-port.
In some embodiments, the difference between the light propagation time from port E to port L and the light propagation time from port H to port M is no more than one-half of the pulse period T of the pulsed laser.
In a second aspect, a method for generating two quantum states, namely polarization state encoding DV-QKD and time-phase encoding DV-QKD, based on the transmitting-end chip comprises the following steps:
the pulse laser produces the pulsed light that the cycle is T, and first intensity modulator carries out the light intensity fine adjustment of pulse one by one to the pulsed light, and the light that second intensity modulator will input is with the light intensity distribution ratio of adjustable proportion, exports two delivery outlets of itself: a port A and a port B;
the first phase modulator increases the phase factor of the light field entering from the A port
Figure BDA0002868687620000068
Then, the output is output to the output port C of the device; the second phase modulator increases the phase factor of the light field entering from the port B
Figure BDA0002868687620000069
Then, the output is output to an output port D of the device;
the first 1 x 2 beam splitter outputs the light input from the port C to its two output ports at a pre-designed light intensity distribution ratio: ports E and F; the second 1 × 2 beam splitter outputs the optical power of the light input from the D port to its two output ports at a pre-designed light intensity distribution ratio: a port G and a port H;
the first variable optical attenuator attenuates the light input from the port F by an adjustable attenuation percentage and outputs the light to an output port I of the first variable optical attenuator; the second variable optical attenuator attenuates the light input from the G port by an adjustable attenuation percentage and outputs the light to an output port J of the second variable optical attenuator; the polarization rotation synthesizer outputs light input from the I port to a K port, namely a first external optical fiber coupling port, of an output port of the polarization rotation synthesizer, rotates the polarization direction of light input from the J port by 90 degrees and outputs the light to the K port, and light input from the I port and the J port respectively form TE mode energy components and TM mode energy components of the polarization state of the light output to the external optical fiber;
the delay waveguide prolongs the light propagation time from the port E to the port L of the output port of the delay waveguide according to a preset delay value relative to the light propagation time from the port H to the port M of the output port of the third variable optical attenuator; the third variable optical attenuator attenuates the light input to the port H by an adjustable attenuation percentage and outputs the light to the port M; 2 × 1 50: the 50 splitter couples half of the optical power input at the L port to a 2 x 1 50: and an output port N of the 50 beam splitters, namely a second external optical fiber coupling port N, and couples half of the optical power input by the port M to the port N.
In some embodiments, further comprising the steps of:
when the transmitting end chip generates a polarization state physical degree of freedom quantum state, the state of the K port external coupling port is open, the state of the N port external coupling port is closed, and the working modes of internal devices required by correspondingly generating different polarization state physical degree of freedom quantum states are as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
producing physical freedom quantum states of polarization states
Figure BDA0002868687620000081
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulatorLoading a phase factor on an optical field propagating through it
Figure BDA0002868687620000082
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000083
And satisfy
Figure BDA0002868687620000084
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000085
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000086
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000087
And satisfy
Figure BDA0002868687620000088
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000089
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000810
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200000811
And satisfy
Figure BDA00028686876200000812
Producing physical freedom quantum states of polarization states
Figure BDA00028686876200000813
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000814
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200000815
And satisfy
Figure BDA00028686876200000816
When the transmitting end chip generates a time-phase physical degree of freedom quantum state, the state of the K port external coupling port is closed, the state of the N port external coupling port is opened, and the working modes of internal devices required by correspondingly generating different time-phase physical degree of freedom quantum states are as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000091
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000092
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000093
And satisfy
Figure BDA0002868687620000094
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000095
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000096
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000097
And satisfy
Figure BDA0002868687620000098
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000099
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000910
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200000911
And satisfy
Figure BDA00028686876200000912
Generating time-phase physical degree of freedom quantum states
Figure BDA00028686876200000913
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200000914
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200000915
And satisfy
Figure BDA00028686876200000916
Compared with the prior art, the method has the advantages that:
the DV-QKD transmitting-end chip with the switchable polarization encoding freedom degree and the switchable time-phase encoding freedom degree is realized by passively switching the optical path and the passive device in the chip based on the shared active optical element, two quantum states of the polarization state encoding DV-QKD and the time-phase encoding DV-QKD can be generated, only one design and production scheme is needed, and design and production cost can be effectively reduced. When the QKD technology is deployed in a large scale, the requirements of a plurality of equipment manufacturers on DV-QKD transmitting-end chips can be met, and design and production cost is saved.
Drawings
FIG. 1 is a schematic diagram of an arbitrary vector expression of a Bloch sphere and vector expressions of the intersection of the X-axis, Y-axis, Z-axis and the sphere.
Fig. 2 is a schematic structural diagram of a switchable encoding physical degree of freedom transmitting-side chip for DV-QKD in the embodiment of the present invention.
Detailed Description
Reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the specific embodiments, it will be understood that they are not intended to limit the invention to the embodiments described. On the contrary, it is intended to cover alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. It should be noted that the method steps described herein may be implemented by any functional block or functional arrangement, and that any functional block or functional arrangement may be implemented as a physical entity or a logical entity, or a combination of both.
In order that those skilled in the art will better understand the present invention, the following detailed description of the invention is provided in conjunction with the accompanying drawings and the detailed description of the invention.
Note that: the example to be described next is only a specific example, and does not limit the embodiments of the present invention necessarily to the following specific steps, values, conditions, data, orders, and the like. Those skilled in the art can, upon reading this specification, utilize the concepts of the present invention to construct more embodiments than those specifically described herein.
Referring to fig. 2, an embodiment of the present application provides a transmitting-end chip for discrete variable quantum key distribution (DV-QKD), including:
the pulse laser, the first intensity modulator and the second intensity modulator are connected in sequence, and for convenience of the following description, a first output port of the second intensity modulator is named as an A port, and a second output port of the second intensity modulator is named as a B port;
the first phase modulator is connected with the first output port A of the second intensity modulator, and the output port of the first phase modulator is named as a port C;
the second phase modulator is connected with a second output port B of the second intensity modulator, and an output port of the second phase modulator is named as a port D;
the first 1 x 2 beam splitter connected with the output port C of the first phase modulator names the first output port of the first 1 x 2 beam splitter as port E and the second output port as port F;
the second 1 x 2 beam splitter is connected with the output port D of the second phase modulator, the first output port of the second 1 x 2 beam splitter is named as a port G, and the second output port is named as a port H;
the first variable optical attenuator is connected with a second output port F of the first 1 multiplied by 2 beam splitter, and an output port of the first variable optical attenuator is named as a port I;
the second variable optical attenuator is connected with the first output port G of the second 1 multiplied by 2 beam splitter, and the output port of the second variable optical attenuator is named as a port J;
the output port of the polarization rotation synthesizer is named as a port K, the port K of the output port of the polarization rotation synthesizer is connected with an external optical fiber, and the port K is used as a first external optical fiber coupling port of the transmitting end chip;
the delay waveguide is connected with a first output port E of the first 1X 2 beam splitter, and an output port of the delay waveguide is named as an L port;
a third variable optical attenuator connected with a second output port H of the second 1 multiplied by 2 beam splitter, wherein an output port of the third variable optical attenuator is named as an M port;
and 2 × 1 50 connected to the output port L of the delay waveguide and the output port M of the third variable optical attenuator: 50 beam splitter, 2 × 1 50: the output port of the 50 beam splitter is named as N port, 2 × 1 50: and an output port N of the 50 beam splitters is connected with an external optical fiber, and the port N is used as a second external optical fiber coupling port of the transmitting end chip.
In some embodiments, the first intensity modulator in the present application is preferably a 1 × 1 optical switch, the second intensity modulator is preferably a 1 × 2 optical switch, and the polarization rotating combiner is preferably a 2D grating.
The transmitting end chip for DV-QKD can generate different physical freedom states, and the functions of the specific devices are as follows:
a pulsed laser for: pulsed light of period T is generated.
A first intensity modulator to: the pulsed light entering the first intensity modulator is finely adjusted in light intensity pulse by pulse.
A second intensity modulator to: and outputting the light input into the second intensity modulator to a first output port A and a second output port B of the second intensity modulator according to the light intensity distribution ratio with adjustable proportion.
It should be noted that: the optical power value input to the second intensity modulator minus the inherent loss value of the second intensity modulator is equal to the optical power value at port A plus the optical power value at port B, and the energy conservation law is satisfied.
A first phase modulator to: adding the phase factor to the light field entering from the first output port A of the second intensity modulator
Figure BDA0002868687620000121
And then output to the output port C of the first phase modulator.
A second phase modulator to: adding the phase factor to the light field entering from the second output port B of the second intensity modulator
Figure BDA0002868687620000122
And then output to the output port D of the second phase modulator.
A first 1 x 2 beam splitter for: and outputting the light input from the output port C of the first phase modulator to the first output port E and the second output port F of the first 1X 2 beam splitter according to a preset light intensity distribution ratio.
It should be noted that: the value of the optical power input to the first 1 × 2 beam splitter minus the inherent loss value of the first 1 × 2 beam splitter is equal to the value of the optical power at the first output port E of the first 1 × 2 beam splitter plus the value of the optical power at the second output port F of the first 1 × 2 beam splitter, and the energy conservation law is satisfied.
A second 1 x 2 beam splitter for: and outputting the optical power of the light input from the output port D of the second phase modulator to the first output port G of the second 1 x 2 beam splitter and the second output port H of the second 1 x 2 beam splitter according to a preset light intensity distribution ratio.
It should be noted that: the value of the optical power input to the second 1 × 2 beam splitter minus the inherent loss value of the second 1 × 2 beam splitter is equal to the value of the optical power at the E port of the first output port of the first 1 × 2 beam splitter plus the value of the optical power at the F port of the second output port of the first 1 × 2 beam splitter, and the energy conservation law is satisfied.
A first variable optical attenuator for: the light input from the second output port F of the first 1 × 2 beam splitter is attenuated by an adjustable attenuation percentage and then output to the output port I of the first variable optical attenuator.
A second variable optical attenuator for: the light input from the first output port G of the second 1 × 2 beam splitter is attenuated by an adjustable attenuation percentage and then output to the output port J of the second variable optical attenuator.
A polarization rotating combiner for: the light input from the output port I of the first variable optical attenuator is output to the output port K of the polarization rotation synthesizer, namely the first external optical fiber coupling port, the polarization direction of the light input from the output port J of the second variable optical attenuator is rotated by 90 degrees, and then the light is output to the output port K of the polarization rotation synthesizer, namely the first external optical fiber coupling port K of the transmitting end chip, so that the light input from the I port and the light input from the J port respectively form TE mode energy components and TM mode energy components of the polarization state of the light output to the external optical fiber.
A time delay waveguide for: and according to a pre-designed delay value of the light propagation time from the second output port H of the second 1X 2 beam splitter to the output port M of the third variable optical attenuator, prolonging the light propagation time from the first output port E of the first 1X 2 beam splitter to the output port L of the delay waveguide.
A third variable optical attenuator for: the light input to the second output port H of the second 1 × 2 beam splitter is attenuated by an adjustable attenuation percentage and then output to the output port M of the third variable optical attenuator.
2 × 1 50: a 50 beam splitter for: half of the optical power input from the output port L of the delay waveguide is coupled to a 2 × 1 50: and 50, an output port N of the beam splitter, namely a second external optical fiber coupling port N of the transmitting-end chip, and couples half of the optical power input from an output port M of the third variable optical attenuator to the output port N.
Referring to tables 1 and 2, table 1 describes the device operation modes corresponding to the quantum states required for DV-QKD to generate the polarization state physical degree of freedom, and table 2 describes the device operation modes corresponding to the quantum states required for DV-QKD to generate the time-phase physical degree of freedom. In practical applications, the two physical degrees of freedom referred to in tables 1 and 2 are generally alternatives according to the requirements of the corresponding DV-QKD system.
TABLE 1 operation of devices corresponding to the quantum states required for DV-QKD producing polarization state physical degree of freedom
Figure BDA0002868687620000141
Figure BDA0002868687620000151
From table 1 it can be seen that: when DV-QKD generates polarization state physical freedom degree quantum state, the output port K of the polarization rotation synthesizer is open to the external coupling port, 50 of 2 multiplied by 1: the output port N of the 50 beam splitter is closed to the external coupling port, and the working modes of internal devices required for correspondingly generating different polarization state physical freedom degree quantum states are as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to distribute the optical power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the B port to distribute the light power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Physics of generation of polarization stateDegree of freedom quantum state
Figure BDA0002868687620000152
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000161
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000162
And satisfy
Figure BDA0002868687620000163
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000164
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000165
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000166
And satisfy
Figure BDA0002868687620000167
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000168
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000169
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200001610
And satisfy
Figure BDA00028686876200001611
Producing physical freedom quantum states of polarization states
Figure BDA00028686876200001612
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200001613
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200001614
And satisfy
Figure BDA00028686876200001615
TABLE 2 operation of devices corresponding to the quantum states required to produce DV-QKD for time-phase physical degrees of freedom
Figure BDA00028686876200001616
Figure BDA0002868687620000171
From table 2 it can be seen that: when DV-QKD generates time-phase physical freedom quantum state, the output port K of the polarization rotation synthesizer is closed to the external coupling port, 2 x 1 50: the output port N of the 50 beam splitter is open at an external coupling port, and the working modes of internal devices required for generating different time-phase physical freedom quantum states are as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to distribute the optical power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the B port to distribute the light power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000172
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000181
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000182
And satisfy
Figure BDA0002868687620000183
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000184
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000185
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000186
And satisfy
Figure BDA0002868687620000187
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000188
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000189
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200001810
And satisfy
Figure BDA00028686876200001811
Generating time-phase physical degree of freedom quantum states
Figure BDA00028686876200001812
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200001813
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200001814
And satisfy
Figure BDA00028686876200001815
In practical applications, the following points need to be noted:
1. the state switching frequency of the second intensity modulator connected with the output port of the first intensity modulator is 1/T.
2. The phase change switching frequency of the first phase modulator and the second phase modulator which are respectively connected with the first output port A and the second output port B of the second intensity modulator is 1/T.
3. The ratio of the light intensity of the output port C of the first phase modulator to the first output port E of the first 1 x 2 beam splitter to the light intensity of the output port C of the first phase modulator to the second output port F of the first 1 x 2 beam splitter is equal to the ratio of the light intensity of the output port D of the second phase modulator to the second output port H of the second 1 x 2 beam splitter to the light intensity of the output port D of the second phase modulator to the output port C of the first phase modulator.
4. The optical power distribution ratio of the second output port F of the first 1 × 2 beam splitter to the first output port E of the first 1 × 2 beam splitter is close to or equal to the optical power distribution ratio of the first output port G of the second 1 × 2 beam splitter to the second output port H of the second 1 × 2 beam splitter.
5. The difference between the light propagation time from the first output port E of the first 1 x 2 beam splitter to the output port L of the delay waveguide and the light propagation time from the second output port H of the second 1 x 2 beam splitter to the output port M of the third variable optical attenuator is not more than one half of the pulse period T of the pulse laser.
6. Output port K of the polarization rotation combiner connected to the external optical fiber (first external optical fiber coupling port of the transmitting end chip) and 50 of 2 × 1: the output port N of the 50 beam splitter (the second external fiber coupling port of the transmitting end chip) may be connected to a 2 × 1 optical switch, and the 2 × 1 optical switch may be switched manually or controlled automatically.
The DV-QKD transmitting terminal chip with the switchable polarization encoding freedom degree and the switchable time-phase encoding freedom degree is realized by passively switching the optical path and the passive device in the chip based on the shared active optical element, two quantum states of the polarization encoding DV-QKD and the time-phase encoding DV-QKD can be generated, only one design and production scheme is needed, and design and production cost can be effectively reduced. When the QKD technology is deployed in a large scale, the requirements of a plurality of equipment manufacturers on DV-QKD transmitting-end chips can be met, and design and production cost is saved.
The embodiment of the application provides a method for generating two quantum states of polarization state coding DV-QKD and time-phase coding DV-QKD based on the transmitting end chip, which comprises the following steps:
the pulse laser generates pulse light with a period of T, the first intensity modulator finely adjusts the light intensity of the pulse light entering the first intensity modulator one by one, and the second intensity modulator outputs the light input into the second intensity modulator to a first output port A and a second output port B of the second intensity modulator according to a light intensity distribution ratio with an adjustable proportion; it should be noted that: the optical power value input to the second intensity modulator subtracts the inherent loss value of the second intensity modulator, is equal to the optical power value of the port A plus the optical power value of the port B, and meets the law of energy conservation;
the first phase modulator increases the phase factor of the light field entering from the first output port A of the second intensity modulator
Figure BDA0002868687620000201
Then, the signal is output to an output port C of the first phase modulator; the second phase modulator increases the phase factor of the light field entering from the second output port B of the second intensity modulator
Figure BDA0002868687620000202
Then, the signal is output to an output port D of a second phase modulator;
the first 1 x 2 beam splitter outputs the light input from the output port C of the first phase modulator to the first output port E and the second output port F of the first 1 x 2 beam splitter according to a pre-designed light intensity distribution ratio; note that: the value of the optical power input into the first 1 × 2 beam splitter minus the inherent loss value of the first 1 × 2 beam splitter is equal to the value of the optical power at the first output port E of the first 1 × 2 beam splitter plus the value of the optical power at the second output port F of the first 1 × 2 beam splitter, and the energy conservation law is satisfied;
the second 1 × 2 beam splitter outputs the optical power of the light input from the output port D of the second phase modulator to the first output port G of the second 1 × 2 beam splitter and the second output port H of the second 1 × 2 beam splitter at a pre-designed light intensity distribution ratio; note that: the value of the optical power input into the second 1 x 2 beam splitter minus the inherent loss value of the second 1 x 2 beam splitter is equal to the value of the optical power at the first output port E of the first 1 x 2 beam splitter plus the value of the optical power at the second output port F of the first 1 x 2 beam splitter, and the energy conservation law is satisfied;
the first variable optical attenuator attenuates the light input from the second output port F of the first 1 multiplied by 2 beam splitter by an adjustable attenuation percentage and outputs the light to the output port I of the first variable optical attenuator; the second variable optical attenuator attenuates the light input from the first output port G of the second 1 multiplied by 2 beam splitter by an adjustable attenuation percentage and outputs the light to an output port J of the second variable optical attenuator; the polarization rotation synthesizer outputs light input from an output port I of the first variable optical attenuator to an output port K of the polarization rotation synthesizer, namely a first external optical fiber coupling port, rotates the polarization direction of light input from an output port J of the second variable optical attenuator by 90 degrees, and outputs the light to the output port K of the polarization rotation synthesizer, namely a first external optical fiber coupling port K of the transmitting end chip, so that the light input from the I port and the light input from the J port respectively form a TE mode energy component and a TM mode energy component of the polarization state of the light output to the external optical fiber;
the delay waveguide prolongs the light propagation time from the first output port E of the first 1X 2 beam splitter to the output port L of the delay waveguide according to a preset delay value relative to the light propagation time from the second output port H of the second 1X 2 beam splitter to the output port M of the third variable optical attenuator; the third variable optical attenuator attenuates the light input to the second output port H of the second 1 × 2 beam splitter by an adjustable attenuation percentage and outputs the light to the output port M of the third variable optical attenuator; 2 × 1 50: the 50 splitter couples half of the optical power input at the output port L of the delay waveguide to a 2 x 1 50: and 50, an output port N of the beam splitter, namely a second external optical fiber coupling port N of the transmitting-end chip, and couples half of the optical power input from an output port M of the third variable optical attenuator to the output port N.
Table 1 above describes the operation modes of the devices corresponding to the quantum states required for generating DV-QKD with the polarization state physical degree of freedom, and table 2 describes the operation modes of the devices corresponding to the quantum states required for generating DV-QKD with the time-phase physical degree of freedom. In practical applications, the two physical degrees of freedom referred to in tables 1 and 2 are generally alternatives according to the requirements of the corresponding DV-QKD system.
From table 1 it can be seen that: when DV-QKD generates polarization state physical freedom degree quantum state, the output port K of the polarization rotation synthesizer is open to the external coupling port, 50 of 2 multiplied by 1: the output port N of the 50 beam splitter is closed to the external coupling port, and the working modes of internal devices required for correspondingly generating different polarization state physical freedom degree quantum states are as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to distribute the optical power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the B port to distribute the light power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000221
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000222
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000223
And satisfy
Figure BDA0002868687620000224
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000225
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000226
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000227
And satisfy
Figure BDA0002868687620000228
Producing physical freedom quantum states of polarization states
Figure BDA0002868687620000229
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA00028686876200002210
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200002211
And satisfy
Figure BDA00028686876200002212
Producing physical freedom quantum states of polarization states
Figure BDA00028686876200002213
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000231
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000232
And satisfy
Figure BDA0002868687620000233
From table 2 it can be seen that: when DV-QKD generates time-phase physical freedom quantum state, the output port K of the polarization rotation synthesizer is closed to the external coupling port, 2 x 1 50: the output port N of the 50 beam splitter is open at an external coupling port, and the working modes of internal devices required for generating different time-phase physical freedom quantum states are as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to distribute the optical power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the B port to distribute the light power in a maximized mode, and the first phase modulator and the second phase modulator do not need to load phase factors on a propagating light field and can maintain the voltage value applied by the loaded phase factors.
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000234
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000235
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000236
And satisfy
Figure BDA0002868687620000237
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000238
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000239
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA00028686876200002310
And satisfy
Figure BDA00028686876200002311
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000241
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000242
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000243
And satisfy
Figure BDA0002868687620000244
Generating time-phase physical degree of freedom quantum states
Figure BDA0002868687620000245
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure BDA0002868687620000246
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure BDA0002868687620000247
And satisfy
Figure BDA0002868687620000248
In practical applications, the following points need to be noted:
1. the state switching frequency of the second intensity modulator connected with the output port of the first intensity modulator is 1/T.
2. The phase change switching frequency of the first phase modulator and the second phase modulator which are respectively connected with the first output port A and the second output port B of the second intensity modulator is 1/T.
3. The ratio of the light intensity of the output port C of the first phase modulator to the first output port E of the first 1 x 2 beam splitter to the light intensity of the output port C of the first phase modulator to the second output port F of the first 1 x 2 beam splitter is equal to the ratio of the light intensity of the output port D of the second phase modulator to the second output port H of the second 1 x 2 beam splitter to the light intensity of the output port D of the second phase modulator to the output port C of the first phase modulator.
4. The optical power distribution ratio of the second output port F of the first 1 × 2 beam splitter to the first output port E of the first 1 × 2 beam splitter is close to or equal to the optical power distribution ratio of the first output port G of the second 1 × 2 beam splitter to the second output port H of the second 1 × 2 beam splitter.
5. The difference between the light propagation time from the first output port E of the first 1 x 2 beam splitter to the output port L of the delay waveguide and the light propagation time from the second output port H of the second 1 x 2 beam splitter to the output port M of the third variable optical attenuator is not more than one half of the pulse period T of the pulse laser.
6. Output port K of the polarization rotation combiner connected to the external optical fiber (first external optical fiber coupling port of the transmitting end chip) and 50 of 2 × 1: the output port N of the 50 beam splitter (the second external fiber coupling port of the transmitting end chip) may be connected to a 2 × 1 optical switch, and the 2 × 1 optical switch may be switched manually or controlled automatically.
The embodiment of the application is based on the shared active optical element, two quantum states of the polarization state code DV-QKD and the time-phase code DV-QKD are generated in a mode of passively switching the optical path and the passive device in the chip, only one design and production scheme is needed, and design and production cost can be effectively reduced. When the QKD technology is deployed in a large scale, the requirements of a plurality of equipment manufacturers on DV-QKD transmitting-end chips can be met, and design and production cost is saved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (10)

1. A transmit-side chip for discrete variable quantum key distribution, comprising:
the pulse laser, the first intensity modulator and the second intensity modulator are connected in sequence;
the first phase modulator and the second phase modulator are respectively connected with the second intensity modulator;
a first 1 x 2 beam splitter connected to the first phase modulator, a second 1 x 2 beam splitter connected to the second phase modulator;
the delay waveguide and the first variable optical attenuator are respectively connected with the first 1 multiplied by 2 beam splitter, and the second variable optical attenuator and the third variable optical attenuator are respectively connected with the second 1 multiplied by 2 beam splitter;
the polarization rotation synthesizer is respectively connected with the first variable optical attenuator and the second variable optical attenuator, and the output port of the polarization rotation synthesizer is used as a first external optical fiber coupling port of the transmitting end chip;
2 × 1 50 connected to the delay waveguide and the third variable optical attenuator, respectively: 50 beam splitter, the output port of which is used as the second external optical fiber coupling port of the transmitting end chip,
the transmitting end chip generates two quantum states of polarization state encoding DV-QKD and time-phase encoding DV-QKD.
2. The transmitting-side chip according to claim 1, wherein:
the pulse laser produces the pulsed light that the cycle is T, and first intensity modulator carries out the light intensity fine adjustment of pulse one by one to the pulsed light, and the light that second intensity modulator will input is with the light intensity distribution ratio of adjustable proportion, exports two delivery outlets of itself: a port A and a port B;
the first phase modulator increases the phase factor of the light field entering from the A port
Figure FDA0002868687610000011
Then, the output is output to the output port C of the device; the second phase modulator increases the phase factor of the light field entering from the port B
Figure FDA0002868687610000012
Then, the output is output to an output port D of the device;
the first 1 x 2 beam splitter outputs the light input from the port C to its two output ports at a pre-designed light intensity distribution ratio: ports E and F; the second 1 × 2 beam splitter outputs the optical power of the light input from the D port to its two output ports at a pre-designed light intensity distribution ratio: a port G and a port H;
the first variable optical attenuator attenuates the light input from the port F by an adjustable attenuation percentage and outputs the light to an output port I of the first variable optical attenuator; the second variable optical attenuator attenuates the light input from the G port by an adjustable attenuation percentage and outputs the light to an output port J of the second variable optical attenuator; the polarization rotation synthesizer outputs light input from the I port to a K port, namely a first external optical fiber coupling port, of an output port of the polarization rotation synthesizer, rotates the polarization direction of light input from the J port by 90 degrees and outputs the light to the K port, and light input from the I port and the J port respectively form TE mode energy components and TM mode energy components of the polarization state of the light output to the external optical fiber;
the delay waveguide prolongs the light propagation time from the port E to the port L of the output port of the delay waveguide according to a preset delay value relative to the light propagation time from the port H to the port M of the output port of the third variable optical attenuator; the third variable optical attenuator attenuates the light input to the port H by an adjustable attenuation percentage and outputs the light to the port M; 2 × 1 50: the 50 splitter couples half of the optical power input at the L port to a 2 x 1 50: and an output port N of the 50 beam splitters, namely a second external optical fiber coupling port N, and couples half of the optical power input by the port M to the port N.
3. The transmitting-side chip according to claim 2, wherein: when the transmitting end chip generates a polarization state physical degree of freedom quantum state, the state of the K port external coupling port is open, the state of the N port external coupling port is closed, and the working modes of internal devices required by correspondingly generating different polarization state physical degree of freedom quantum states are as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
producing physical freedom quantum states of polarization states
Figure FDA0002868687610000021
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000031
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000032
And satisfy
Figure FDA0002868687610000033
Producing physical freedom quantum states of polarization states
Figure FDA0002868687610000034
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000035
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000036
And satisfy
Figure FDA0002868687610000037
Producing physical freedom quantum states of polarization states
Figure FDA0002868687610000038
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000039
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000310
And satisfy
Figure FDA00028686876100000311
Producing physical freedom quantum states of polarization states
Figure FDA00028686876100000312
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA00028686876100000313
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000314
And satisfy
Figure FDA00028686876100000315
4. The transmitting-side chip according to claim 2, wherein: when the transmitting end chip generates a time-phase physical degree of freedom quantum state, the state of the K port external coupling port is closed, the state of the N port external coupling port is opened, and the working modes of internal devices required by correspondingly generating different time-phase physical degree of freedom quantum states are as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000041
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000042
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000043
And satisfy
Figure FDA0002868687610000044
Generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000045
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000046
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000047
And satisfy
Figure FDA0002868687610000048
Generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000049
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA00028686876100000410
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000411
And satisfy
Figure FDA00028686876100000412
Generating time-phase physical degree of freedom quantum states
Figure FDA00028686876100000413
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA00028686876100000414
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000415
And satisfy
Figure FDA00028686876100000416
5. The transmitting-side chip according to claim 2, wherein: the state switching frequency of the second intensity modulator is 1/T, and the phase change switching frequency of the first phase modulator and the second phase modulator is 1/T.
6. The transmitting-side chip according to claim 2, wherein: the ratio of the light intensity from the port C to the port E to the light intensity from the port C to the port F is equal to the ratio of the light intensity from the port D to the port H to the light intensity from the port D to the port C.
7. The transmitting-side chip according to claim 2, wherein: and the optical power distribution ratio of the port F to the port E is close to or equal to the optical power distribution ratio of the port G to the port H.
8. The transmitting-side chip according to claim 2, wherein: the difference between the light propagation time from the port E to the port L and the light propagation time from the port H to the port M does not exceed one half of the pulse period T of the pulse laser.
9. A method for generating two quantum states of polarization state encoding DV-QKD and time-phase encoding DV-QKD based on the transmitting-side chip of claim 1, comprising the steps of:
the pulse laser produces the pulsed light that the cycle is T, and first intensity modulator carries out the light intensity fine adjustment of pulse one by one to the pulsed light, and the light that second intensity modulator will input is with the light intensity distribution ratio of adjustable proportion, exports two delivery outlets of itself: a port A and a port B;
the first phase modulator increases the phase factor of the light field entering from the A port
Figure FDA0002868687610000051
Then, the output is output to the output port C of the device; the second phase modulator increases the phase factor of the light field entering from the port B
Figure FDA0002868687610000052
Then, the output is output to an output port D of the device;
the first 1 x 2 beam splitter outputs the light input from the port C to its two output ports at a pre-designed light intensity distribution ratio: ports E and F; the second 1 × 2 beam splitter outputs the optical power of the light input from the D port to its two output ports at a pre-designed light intensity distribution ratio: a port G and a port H;
the first variable optical attenuator attenuates the light input from the port F by an adjustable attenuation percentage and outputs the light to an output port I of the first variable optical attenuator; the second variable optical attenuator attenuates the light input from the G port by an adjustable attenuation percentage and outputs the light to an output port J of the second variable optical attenuator; the polarization rotation synthesizer outputs light input from the I port to a K port, namely a first external optical fiber coupling port, of an output port of the polarization rotation synthesizer, rotates the polarization direction of light input from the J port by 90 degrees and outputs the light to the K port, and light input from the I port and the J port respectively form TE mode energy components and TM mode energy components of the polarization state of the light output to the external optical fiber;
the delay waveguide prolongs the light propagation time from the port E to the port L of the output port of the delay waveguide according to a preset delay value relative to the light propagation time from the port H to the port M of the output port of the third variable optical attenuator; the third variable optical attenuator attenuates the light input to the port H by an adjustable attenuation percentage and outputs the light to the port M; 2 × 1 50: the 50 splitter couples half of the optical power input at the L port to a 2 x 1 50: and an output port N of the 50 beam splitters, namely a second external optical fiber coupling port N, and couples half of the optical power input by the port M to the port N.
10. The method of claim 9, further comprising the steps of:
when the transmitting end chip generates a polarization state physical degree of freedom quantum state, the state of the K port external coupling port is open, the state of the N port external coupling port is closed, and the working modes of internal devices required by correspondingly generating different polarization state physical degree of freedom quantum states are as follows:
generating a polarization state physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a polarization state physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
producing physical freedom quantum states of polarization states
Figure FDA0002868687610000061
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000062
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000063
And satisfy
Figure FDA0002868687610000064
Producing physical freedom quantum states of polarization states
Figure FDA0002868687610000065
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000071
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000072
And satisfy
Figure FDA0002868687610000073
GeneratingPhysical degree of freedom quantum state of polarization state
Figure FDA0002868687610000074
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000075
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000076
And satisfy
Figure FDA0002868687610000077
Producing physical freedom quantum states of polarization states
Figure FDA0002868687610000078
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000079
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000710
And satisfy
Figure FDA00028686876100000711
When the transmitting end chip generates a time-phase physical degree of freedom quantum state, the state of the K port external coupling port is closed, the state of the N port external coupling port is opened, and the working modes of internal devices required by correspondingly generating different time-phase physical degree of freedom quantum states are as follows:
generating a time-phase physical degree of freedom quantum state |0 >: the second intensity modulator enables the A port to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating a time-phase physical degree of freedom quantum state |1 >: the second intensity modulator enables the port B to maximally distribute light power, and the first phase modulator and the second phase modulator do not need to load phase factors on a transmitted light field and maintain the voltage value applied by the loaded phase factors;
generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000081
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000082
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000083
And satisfy
Figure FDA0002868687610000084
Generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000085
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA0002868687610000086
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA0002868687610000087
And satisfy
Figure FDA0002868687610000088
Generating time-phase physical degree of freedom quantum states
Figure FDA0002868687610000089
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA00028686876100000810
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000811
And satisfy
Figure FDA00028686876100000812
Generating time-phase physical degree of freedom quantum states
Figure FDA00028686876100000813
The second intensity modulator makes the A port and the B port distribute light power in equal proportion, and the first phase modulator loads phase factors on a light field propagating through the first phase modulator
Figure FDA00028686876100000814
Second phase modulator loading phase factor loads phase factor for optical field propagating through it
Figure FDA00028686876100000815
And satisfy
Figure FDA00028686876100000816
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