CN114401089B - Adjustable time delay interferometer and quantum key distribution system - Google Patents
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Abstract
An adjustable delay interferometer comprises a first beam splitter BS1, a second beam splitter BS2, a polarization light path selection module POSM and a polarization rotation module PRM, wherein an input port of the first beam splitter BS1 is used as an input port of the interferometer, a second output port of the first beam splitter BS1 is connected with a first port of a polarization light path selection module POSM, and a fourth port of a polarization light path selection module POSM is connected with a second input port of the second beam splitter BS2 to form an unequal arm Mach-Zehnder interferometer; the invention also discloses a quantum key distribution system, which comprises a polarization light path selection module POSM and a polarization rotation module PRM which form an adjustable delay loop ADL with a basic delay of T. Compared with the prior art, the invention can effectively realize large-scale delay adjustment through polarization selection, can meet the randomness and high length of delay selection, and can optimize the L value to maximize the key rate of the protocol. The adjustable delay interferometer has simple structure and stable performance, and can ensure the wide application of RRDPS-QKD protocol.
Description
Technical Field
The invention relates to the technical field of quantum phase encoding, in particular to an adjustable delay interferometer and a quantum key distribution system.
Background
The quantum key distribution protocol (quantum key distribution, QKD) can provide unconditionally secure key distribution for both parties in remote communications, with information theory security guaranteed by the basic principles of quantum mechanics. Wherein the hessian-burg uncertainty principle ensures that all eavesdropping actions will cause the change of the quantum state transmitted in the channel, thereby generating bit errors. The information quantity of the original secret key obtained by the eavesdropper is estimated according to the error code, so that the safety of the communication process is ensured, and the furthest transmission distance of the two communication parties is reached. Signal perturbation is thus a necessary monitoring factor in all existing quantum key distribution protocols to constrain potential information leakage. The Round-robin differential phase quantum key distribution protocol (Round-robin-DIFFERENTIAL PHASE SHIFT QKD, RRDPS-QKD), which cuts off the link between phase errors and bit errors and does not require estimation of phase errors by monitoring the bit errors of channel disturbances, is in principle very robust to channel disturbances of large data block pulses and is therefore called high fault-tolerant quantum key distribution protocol. However, the RRDPS-QKD protocol places high demands on the receiving means of the device. The receiving-side interferometer needs to have multiple delays, and the number of pulse delays that it can accommodate directly determines the key rate, fault tolerance and security of the protocol. The number of selectable delays and the maximum amount of delay for the receive-side interferometer of the prior art are determined so that the maximum value that can be reached by the pulse loop-back length L of the RRDPS-QKD protocol is fixed. A prior art receiving-side interferometer is shown in fig. 1, and this approach uses 4 kinds of delay interferometers, and uses 1×4bs to randomly select different delay paths. However, the passively selected unidirectional adjustable delay interference device consumes a large number of single photon detectors, has a small delay selection range, has a maximum L value of only 5, and has no obvious improvement on tolerance to error codes.
Since the maximum amount of delay of the interferometer in the prior art is determined, i.e. the L value is fixed, the fixed L value cannot be used to optimize the key rate of the protocol. In addition, the interferometer for realizing various time delays in the prior art has a huge and complex structure, increases the complexity and cost of the system and reduces the practicability of the protocol.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides an adjustable delay interferometer and a quantum key distribution system, which are used for solving the technical defects that the maximum delay amount of the interferometer in the prior art is determined, namely, an L value is fixed, the fixed L value cannot be used for optimizing the key rate of a protocol, and the interferometer has a huge and complex structure.
The invention provides an adjustable delay interferometer and a quantum key distribution system, which are as follows:
the technical scheme of the invention is realized as follows:
The adjustable time delay interferometer comprises a first beam splitter BS1, a second beam splitter BS2, a polarization light path selection module POSM and a polarization rotation module PRM, wherein the first beam splitter BS1 comprises an input port, a first output port and a second output port, the second beam splitter BS2 comprises a first input port, a second input port, a first output port and a second output port, the input port of the first beam splitter BS1 is used as the input port of the interferometer, the first output port of the first beam splitter BS1 is directly connected with the first input port of the second beam splitter BS2 through an optical fiber, the second output port of the first beam splitter BS1 is connected with the first port of the polarization light path selection module POSM, and the fourth port of the polarization light path selection module POSM is connected with the second input port of the second beam splitter BS2 to form the unequal arm Mach-Zehnder interferometer; the first output port and the second output port of the second beam splitter BS2 are respectively used as two output ports of the interferometer, the second port and the third port of the polarization light path selection module POSM are respectively connected with the first port and the second port of the polarization rotation module PRM, the polarization light path selection module POSM and the polarization rotation module PRM form an adjustable delay loop ADL with a basic delay of T, and are positioned on a long arm of the interferometer, and are used for changing the time of the photons circulating in the interferometer by modulating the polarization state of the photons, so that the delay of the interferometer is N times of T.
Preferably, the structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a first polarization beam splitter PBS1, the polarization rotation module PRM includes a first optical switch OS1 and a second optical switch OS2, and a first port, a second port, a third port, and a fourth port of the first polarization beam splitter PBS1 are respectively used as a first port, a second port, a third port, and a fourth port of the polarization light path selection module POSM, where polarization maintaining fibers of the fourth port are welded at 90 °; the second port of the first optical switch OS1 and the second port of the second optical switch OS2 are connected after being welded by 90 ° optical fibers to form a path a, the third port of the first optical switch OS1 and the third port of the second optical switch OS2 are directly connected to form a path b, the lengths of the path a and the path b are the same, the first port of the first optical switch OS1 and the first port of the second optical switch OS2 are respectively used as the second port and the first port of the polarization rotation module PRM, and the loop formed by the polarization light path selection module POSM and the polarization rotation module PRM is basically delayed to be T.
Preferably, the structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a second polarization beam splitter PBS2, the polarization rotation module PRM includes a first circulator CIR1, a third polarization beam splitter PBS3, and a first phase modulator PM1, and a first port, a second port, a third port, and a fourth port of the second polarization beam splitter PBS1 are respectively used as a first port, a second port, a third port, and a fourth port of the polarization light path selection module POSM, where polarization maintaining fibers L1 of the fourth port are welded at 90 °; the first port and the third port of the first circulator CIR1 are respectively used as a second port and a first port of the polarization rotation module PRM, and the second port of the first circulator CIR1 is connected with the first port of the third polarization beam splitter PBS3 through 45-degree fusion welding of a polarization maintaining optical fiber; the second port and the third port of the third polarization beam splitter PBS3 are connected through the first phase modulator PM1 and the polarization maintaining fiber to form a sagnac loop, the basic delay of a loop formed by the polarization light path selection module POSM and the polarization rotation module PRM is T, the length Lc of the loop structure formed by the first circulator CIR1 and the second polarization beam splitter PBS2, the length L1 of the optical fiber between the first circulator CIR1 and the third polarization beam splitter PBS3 and the length Ls of the sagnac loop are 2 times, and the pulse propagation time corresponding to the length formed by the length Ls of the sagnac loop, namely t= (lc+2l1+ls)/c, wherein c is the propagation speed of light in the optical fiber.
Preferably, the structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a second circulator CIR2 and a fourth polarization beam splitter PBS4, the polarization rotation module PRM includes a fifth polarization beam splitter PBS5, a second phase modulator PM2 and a reflecting mirror M, a first port and a third port of the second circulator CIR2 are respectively used as a first port and a fourth port of the polarization light path selection module POSM, and a second port and a third port of the fourth polarization beam splitter PBS3 are respectively used as a second port and a third port of the polarization light path selection module POSM; the second port of the second circulator CIR2 is connected with the first port of the fourth polarization beam splitter PBS4 through an optical fiber L2; the first port of the fifth polarization beam splitter PBS5 and the port of the mirror M are respectively used as a first port and a second port of the PRM; the second port of the fourth polarization beam splitter PBS4 is connected with the first port of the fifth polarization beam splitter PBS5 through 45-degree fusion welding of the polarization maintaining optical fiber L3; the second port and the third port of the fifth polarization beam splitter PBS5 are connected through a second phase modulator PM2 and a polarization maintaining fiber to form a Sagnac loop; the third port of the fourth polarization beam splitter PBS4 is connected to a mirror M via an optical fiber L4.
The invention also provides a quantum key distribution system, which comprises a transmitting end Alice and a receiving end Bob, wherein the receiving end Bob comprises any one of the adjustable delay interferometers, the transmitting end Alice comprises a laser LD, an intensity modulator IM, a phase modulator PM and an attenuator ATT which are sequentially connected, the transmitting end Alice is connected with an input port of the adjustable delay interferometer of the receiving end Bob through an optical fiber channel, and two output ports of the adjustable delay interferometer are respectively connected with a single photon detector SPD.
Compared with the prior art, the invention has the following beneficial effects:
The adjustable delay interferometer and the quantum key distribution system effectively realize large-scale delay adjustment through polarization selection, can meet the randomness and high length of delay selection, and can optimize the L value to maximize the key rate of a protocol. The adjustable delay interferometer has simple structure and stable performance, and can ensure the wide application of RRDPS-QKD protocol.
Drawings
FIG. 1 is a schematic diagram of a prior art receiving-end interferometer;
FIG. 2 is a schematic diagram of an adjustable delay interferometer of the present invention;
FIG. 3 is a schematic diagram of a first embodiment of an adjustable delay loop of the present invention;
FIG. 4 is a schematic diagram of a second embodiment of an adjustable delay loop of the present invention;
FIG. 5 is a schematic diagram of a third embodiment of an adjustable delay loop of the present invention;
fig. 6 is a schematic diagram of a quantum key distribution system of the present invention.
Detailed Description
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.
As shown in fig. 2, an adjustable delay interferometer includes a first beam splitter BS1, a second beam splitter BS2, a polarization optical path selection module POSM and a polarization rotation module PRM, where the first beam splitter BS1 includes an input port, a first output port, and a second output port, the second beam splitter BS2 includes a first input port, a second input port, a first output port, and a second output port, the input port of the first beam splitter BS1 is used as the input port of the interferometer, the first output port of the first beam splitter BS1 is directly connected with the first input port of the second beam splitter BS2 through an optical fiber, the second output port of the first beam splitter BS1 is connected with the first port of the polarization optical path selection module POSM, and the fourth port of the polarization optical path selection module POSM is connected with the second input port of the second beam splitter BS2, so as to form an unequal arm mach-zehnder interferometer; the first output port and the second output port of the second beam splitter BS2 are respectively used as two output ports of the interferometer, the second port and the third port of the polarization light path selection module POSM are respectively connected with the first port and the second port of the polarization rotation module PRM, the polarization light path selection module POSM and the polarization rotation module PRM form an adjustable delay loop ADL with a basic delay of T, and are positioned on a long arm of the interferometer, and are used for changing the time of the photons circulating in the interferometer by modulating the polarization state of the photons, so that the delay of the interferometer is N times of T.
The specific delay adjustment process is as follows:
The optical pulse enters the unequal arm Mach-Zehnder interferometer from the input port of the first beam splitter BS1, is split by the first beam splitter BS1 into sub-pulses P1 and P2 of the same amplitude and polarization, wherein the short arm of the P1 walk interferometer reaches the second beam splitter BS2, the long arm of the P2 walk interferometer enters from the first port POSM, and is looped back to propagate in an adjustable delay loop ADL consisting of POSM and PRM. The polarization state of P2 is switched to be horizontal or vertical polarization through the PRM, so that the number of turns N of P2 propagating in the adjustable delay loop is adjusted, and the delay of P2 is N x T. Finally, P2 exits from the fourth port POSM and then reaches the second beam splitter BS2, delayed by N x T from the time P1 reaches the second beam splitter BS 2.
As shown in fig. 3, an embodiment of the adjustable delay loop of the present invention is as follows:
The structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a first polarization beam splitter PBS1, the polarization rotation module PRM includes a first optical switch OS1 and a second optical switch OS2, and a first port, a second port, a third port, and a fourth port of the first polarization beam splitter PBS1 are respectively used as a first port, a second port, a third port, and a fourth port of the polarization light path selection module POSM, where polarization maintaining fibers of the fourth port are welded at 90 °; the second port of the first optical switch OS1 and the second port of the second optical switch OS2 are connected after being welded by 90 ° optical fibers to form a path a, the third port of the first optical switch OS1 and the third port of the second optical switch OS2 are directly connected to form a path b, the lengths of the path a and the path b are the same, the first port of the first optical switch OS1 and the first port of the second optical switch OS2 are respectively used as the second port and the first port of the polarization rotation module PRM, and the loop formed by the polarization light path selection module POSM and the polarization rotation module PRM is basically delayed to be T.
An embodiment one delay adjustment process includes:
The light pulse P2 of horizontal polarization state H enters from the first port POSM and propagates counter-clockwise within the adjustable delay loop. P2 is first transmitted by PBS1 and exits the third port of POSM into OS1. When the states of OS1 and OS2 are controlled to make P2 travel path a, the polarization state of P2 becomes vertical polarization V, the second port entering PBS1 after OS2 is transmitted, and finally the polarization state after passing through the 90 ° fusion point becomes horizontal polarization H, at this time, P2 propagates only one turn in the adjustable delay loop, and the delay amount is T. When the states of OS1 and OS2 are controlled to make P2 travel path b, the polarization state of P2 is still horizontal polarization H, the P2 is reflected by the second port of the PBS1 after passing through OS2, and becomes vertical polarization V to propagate in the adjustable delay loop in the counterclockwise direction again, at this time, when the states of OS1 and OS2 are controlled to make P2 travel path b, P2 arrives at PBS1 again, the P2 is transmitted from the second port of PBS1 due to the vertical polarization V, and finally becomes horizontal polarization H after passing through the 90 ° fusion point, at this time, P2 propagates 2 turns in the adjustable delay loop, and the delay amount is 2T. And when N >2, the states of the OS1 and the OS2 are controlled so that the P2 propagates the first circle and the N-th circle of time path b in the adjustable delay loop, and the delay of the P2 can be adjusted to be N x T when the P2-th circle to the N-1-th circle of time path a. The following table is the relationship between the delay amount of P2 and the number of turns it propagates in the adjustable delay loop and the path each turn takes in the PRM:
。
as shown in fig. 4, a second embodiment of the adjustable delay loop of the present invention:
The structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a second polarization beam splitter PBS2, the polarization rotation module PRM includes a first circulator CIR1, a third polarization beam splitter PBS3, and a first phase modulator PM1, and a first port, a second port, a third port, and a fourth port of the second polarization beam splitter PBS1 are respectively used as a first port, a second port, a third port, and a fourth port of the polarization light path selection module POSM, where polarization maintaining fibers L1 of the fourth port are welded at 90 °; the first port and the third port of the first circulator CIR1 are respectively used as a second port and a first port of the polarization rotation module PRM, and the second port of the first circulator CIR1 is connected with the first port of the third polarization beam splitter PBS3 through 45-degree fusion welding of a polarization maintaining optical fiber; the second port and the third port of the third polarization beam splitter PBS3 are connected through the first phase modulator PM1 and the polarization maintaining fiber to form a sagnac loop, the basic delay of a loop formed by the polarization light path selection module POSM and the polarization rotation module PRM is T, the length Lc of the loop structure formed by the first circulator CIR1 and the second polarization beam splitter PBS2, the length L1 of the optical fiber between the first circulator CIR1 and the third polarization beam splitter PBS3 and the length Ls of the sagnac loop are 2 times, and the pulse propagation time corresponding to the length formed by the length Ls of the sagnac loop, namely t= (lc+2l1+ls)/c, wherein c is the propagation speed of light in the optical fiber.
The second delay adjustment process of the embodiment includes:
The light pulse P2 of horizontal polarization state H enters from the first port POSM and propagates counter-clockwise within the adjustable delay loop. P2 is first transmitted by PBS1 and exits the third port of POSM into the PRM for polarization rotation. First from the first port of CIR1, and out from the second port, the polarization state becomes 45 linear polarization after 45 polarization rotation. The 45 polarization state can be written as Wherein the H component is in a horizontal polarization state and propagates along the slow axis(s) of the polarization-maintaining fiber; the V component is in a vertical polarization state and propagates along the fast axis (f) of the polarization maintaining fiber. P2 enters from the first port of PBS3, the H component is transmitted out from the second port of PBS3, propagates in the counterclockwise direction within the Sagnac loop, and is denoted as pulse P21; the V component is reflected off the third port of PBS3 and propagates in a clockwise direction within the sagnac loop, denoted as pulse P22. Wherein P21 modulates phase/>, when passing through PM1P22 is phase-not modulated when passing through PM1, and is synthesized into a beam of light pulse P2' when respectively returning to PBS3 again, and after 45-degree polarization rotation, the polarization state becomes/>。
When modulating phaseWhen the polarization state of P2' becomes vertical polarization V, when the signal reaches CIR1, the signal enters the third port from the second port, then is transmitted from the second port to the fourth port of PBS2, and finally exits from the fourth port of POSM after 90 ° polarization rotation, the polarization state is horizontal polarization H, and the time delay is t=t= (lc+2l1+ls)/c, which is equivalent to 1 turn of propagation in the adjustable delay loop.
When modulating phaseWhen the polarization state of P2' becomes horizontal polarization H, the light enters the third port from the second port when the light reaches CIR1, then is reflected from the second port of PBS2 to the third port, and enters the PRM again for polarization rotation. When modulating phase/>When the polarization state of P2' becomes vertical polarization V, when the signal reaches CIR1, the signal enters the third port from the second port, then is transmitted from the second port to the fourth port of PBS2, and finally exits from the fourth port of POSM after 90 ° polarization rotation, the polarization state is horizontal polarization H, and the time delay is t=2t=2 (lc+2l1+ls)/c, which is equivalent to 2 times of propagation in an adjustable delay loop.
By analogy when N >2, by adjusting the phaseAnd enabling the polarization of the second port entering the PBS2 to be horizontal polarization H when the P2 propagates from the first circle to the N-1 th circle in the adjustable delay loop, enabling the polarization of the second port entering the PBS2 to be vertical polarization V when the P2 propagates from the N-1 th circle, and adjusting the delay of the P2 to be N T. The following table is the delay amount of P2 and the number of turns of the delay loop and the PM1 modulation phase/>, of each turnIs the relation of:
。
as shown in fig. 5, an embodiment of the adjustable delay loop of the present invention is three:
The structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a second circulator CIR2 and a fourth polarization beam splitter PBS4, the polarization rotation module PRM includes a fifth polarization beam splitter PBS5, a second phase modulator PM2 and a reflecting mirror M, a first port and a third port of the second circulator CIR2 are respectively used as a first port and a fourth port of the polarization light path selection module POSM, and a second port and a third port of the fourth polarization beam splitter PBS3 are respectively used as a second port and a third port of the polarization light path selection module POSM; the second port of the second circulator CIR2 is connected with the first port of the fourth polarization beam splitter PBS4 through an optical fiber L2; the first port of the fifth polarization beam splitter PBS5 and the port of the mirror M are respectively used as a first port and a second port of the PRM; the second port of the fourth polarization beam splitter PBS4 is connected with the first port of the fifth polarization beam splitter PBS5 through 45-degree fusion welding of the polarization maintaining optical fiber L3; the second port and the third port of the fifth polarization beam splitter PBS5 are connected through a second phase modulator PM2 and a polarization maintaining fiber to form a Sagnac loop; the third port of the fourth polarization beam splitter PBS4 is connected to a mirror M via an optical fiber L4.
The second delay adjustment process of the embodiment includes:
Light pulse P2 of horizontal polarization state H enters from the first port POSM, first from the first port to the second port of CIR2, and is transmitted from the first port of PBS4 to the first port of PBS5, after 45 ° polarization rotation, the polarization state changes to 45 ° linear polarization. Wherein the H component is transmitted out of the second port of PBS5, propagates in a counterclockwise direction within the Sagnac loop, denoted as pulse P21; the V component is reflected off the third port of PBS5 and propagates in a clockwise direction within the sagnac loop, denoted as pulse P22. Wherein P21 modulates phase when passing through PM2 P22 is phase-not modulated when passing through PM2, and is synthesized into a beam of light pulse P2' when respectively returning to PBS5 again, and after 45 DEG polarization rotation, the polarization state becomes/>。
When modulating phaseWhen the polarization state of P2' becomes horizontal polarization H, it is directly transmitted when reaching PBS4, enters the first port from the second port, is output via CIR2, and finally exits from the fourth port POSM, the polarization state is horizontal polarization H, and the time delay experienced is t= (2l2+2l3+ls)/c.
When modulating phaseWhen the polarization state of P2' becomes vertical polarization V, the light reflected from the second port enters the third port when reaching the PBS4, then the light is reflected by the reflector M and returns to the third port of the PBS4, the polarization state becomes horizontal polarization H after being reflected to the second port, and the light enters the PRM again for polarization rotation. When modulating phase/>When the polarization state of P2' becomes horizontal polarization H, the light is directly transmitted when reaching PBS4, enters the first port from the second port, is output through CIR2, finally exits from the fourth port POSM, the polarization state is horizontal polarization H, and the time delay is t= [2L2+2 (2L3+Ls) +2L4]/c.
Analogize to when N >2, P2 modulates the phase from the first time to the N-1 th time in the Sagnac loopNth modulation phase/>The delay of P2 can be adjusted to be t= [2L2+N (2L3+Ls) +2 (N-1) L4]/c. The following table is the delay amount of P2 and the number of turns of the delay loop and the PM1 modulation phase/>, of each turnIs the relation of:
，
the delay amount can be matched with the pulse period by setting the length of each optical fiber.
As shown in fig. 6, the invention further provides a quantum key distribution system, which comprises a transmitting end Alice and a receiving end Bob, wherein the receiving end Bob comprises any one of the adjustable delay interferometers, the transmitting end Alice comprises a laser LD, an intensity modulator IM, a phase modulator PM and an attenuator ATT which are sequentially connected, the transmitting end Alice is connected with an input port of the adjustable delay interferometer of the receiving end Bob through an optical fiber channel, and two output ports of the adjustable delay interferometer are respectively connected with a single photon detector SPD.
By integrating the embodiments of the invention, the adjustable delay interferometer and the quantum key distribution system can effectively realize large-scale delay adjustment through polarization selection, can meet the randomness and high length of delay selection, and can optimize the L value to maximize the key rate of a protocol. The adjustable delay interferometer has simple structure and stable performance, and can ensure the wide application of RRDPS-QKD protocol.
Claims (2)
1. The adjustable time delay interferometer is characterized by comprising a first beam splitter BS1, a second beam splitter BS2, a polarization light path selection module POSM and a polarization rotation module PRM, wherein the first beam splitter BS1 comprises an input port, a first output port and a second output port, the second beam splitter BS2 comprises a first input port, a second input port, a first output port and a second output port, the input port of the first beam splitter BS1 is used as the input port of the interferometer, the first output port of the first beam splitter BS1 is directly connected with the first input port of the second beam splitter BS2 through an optical fiber, the second output port of the first beam splitter BS1 is connected with the first port of the polarization light path selection module POSM, and the fourth port of the polarization light path selection module POSM is connected with the second input port of the second beam splitter BS2 to form the unequal arm Mach-Zehnder interferometer; the first output port and the second output port of the second beam splitter BS2 are respectively used as two output ports of the interferometer, the second port and the third port of the polarization light path selection module POSM are respectively connected with the first port and the second port of the polarization rotation module PRM, the polarization light path selection module POSM and the polarization rotation module PRM form an adjustable delay loop ADL with a basic delay of T, and are positioned on a long arm of the interferometer, and are used for changing the time of the photon circulating in the interferometer by modulating the polarization state of the photon, so as to adjust the delay of the interferometer to be N times of T, and the structure of the adjustable delay loop ADL is as follows: the polarization light path selection module POSM is a second polarization beam splitter PBS2, the polarization rotation module PRM includes a first circulator CIR1, a third polarization beam splitter PBS3, and a first phase modulator PM1, and a first port, a second port, a third port, and a fourth port of the second polarization beam splitter PBS2 are respectively used as a first port, a second port, a third port, and a fourth port of the polarization light path selection module POSM, where polarization maintaining fibers L1 of the fourth port are welded at 90 °; the first port and the third port of the first circulator CIR1 are respectively used as a second port and a first port of the polarization rotation module PRM, and the second port of the first circulator CIR1 is connected with the first port of the third polarization beam splitter PBS3 through 45-degree fusion welding of a polarization maintaining optical fiber; the second port and the third port of the third polarization beam splitter PBS3 are connected through the first phase modulator PM1 and the polarization maintaining fiber to form a sagnac loop, the basic delay of a loop formed by the polarization light path selection module POSM and the polarization rotation module PRM is T, the length Lc of the loop structure formed by the first circulator CIR1 and the second polarization beam splitter PBS2, the length L1 of the optical fiber between the first circulator CIR1 and the third polarization beam splitter PBS3 and the length Ls of the sagnac loop are 2 times, and the pulse propagation time corresponding to the length formed by the length Ls of the sagnac loop, namely t= (lc+2l1+ls)/c, wherein c is the propagation speed of light in the optical fiber.
2. The quantum key distribution system comprises a transmitting end Alice and a receiving end Bob, wherein the receiving end Bob comprises an adjustable delay interferometer according to claim 1, and the quantum key distribution system is characterized in that the transmitting end Alice comprises a laser LD, an intensity modulator IM, a phase modulator PM and an attenuator ATT which are sequentially connected, the transmitting end Alice is connected with an input port of the adjustable delay interferometer of the receiving end Bob through a fiber channel, and two output ports of the adjustable delay interferometer are respectively connected with a single photon detector SPD.
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| CN114697021A (en) * | 2022-03-17 | 2022-07-01 | 银川产业技术研究院 | Light quantum coding and decoding device and quantum key distribution system |
| CN114460692B (en) * | 2022-04-12 | 2022-07-01 | 浙江九州量子信息技术股份有限公司 | Polarization-independent light path adjusting device |
| CN114584224B (en) * | 2022-04-28 | 2022-08-05 | 杭州慧明量子通信技术有限公司 | Quantum key distribution phase encoding device |
| CN114579082B (en) * | 2022-05-06 | 2022-07-19 | 北京中科国光量子科技有限公司 | Quantum random number generator based on laser phase noise |
| CN115883089B (en) * | 2023-01-29 | 2023-06-16 | 北京中科国光量子科技有限公司 | Polarization selective phase modulation interferometer, quantum key distribution device, system and network |
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