CN103199994B - The Active phase compensate method of Combisweep and device - Google Patents
The Active phase compensate method of Combisweep and device Download PDFInfo
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Abstract
The present invention discloses a kind of Active phase compensate method and device of Combisweep, be specially and add an adapter ring at Alice end, the ring that adapter ring is held with Alice and Bob is respectively interfered, scanning obtains the interference curve of Alice end and Bob end respectively, thus obtain the phase drift parameter of phase-modulator, more respectively Active phase compensate is carried out to Alice and Bob end.In the present invention, Alice and Bob only needs to carry out single pass respectively, shortens sweep time, and improves the fail safe of system.The present invention also reduces time of phasescan and complexity and independent scan for realizing Alice and Bob end avoids phase place to remap attack or side channel analysis.
Description
Technical Field
The invention relates to the field of quantum key distribution, in particular to an active phase compensation method and device for joint scanning.
Background
Phase drift is an inherent problem of phase-encoded Quantum Key Distribution (QKD) systems and is one of the important factors affecting the practical performance of QKD systems. Compensation scheme for single phase scanning active phase: it is assumed that the voltage loaded by the phase modulator at Alice and the modulated phase are linear, so that only the interference curve at Bob is scanned. In practical devices the voltage applied by the phase modulator and the phase modulated are not linear, so an active phase compensation scheme of the four-phase scanning method is proposed. However, the four-phase scanning method needs to scan the interference curve at the Bob end for 4 times, which increases the time and complexity of phase scanning, and needs Bob to transmit the scanning result to Alice through a public channel, so that Eve can acquire the phase scanning information, and provides possibility for implementing phase remapping attack or side channel attack, which causes related security problems.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention firstly provides an active phase compensation method of combined scanning, which shortens the scanning time while improving the system safety.
In order to realize the purpose, the technical scheme is as follows:
an intermediate ring is added at an Alice end and is an MZ interference ring or an FM interference ring, the intermediate ring interferes with rings at the Alice end and a Bob end respectively, interference curves of the Alice end and the Bob end are obtained through scanning, so that phase drift parameters of a phase modulator are obtained, and then the Alice end and the Bob end are subjected to active phase compensation respectively.
And respectively converting the phase shift of the Alice end and the Bob end relative to the intermediate ring, and comparing the phase shift of the Alice end and the Bob end with the intermediate ring to obtain phase shift parameters of the Alice end and the Bob end. At this time, the phase scanning of the Alice end is completely completed locally, and the phase scanning does not pass through a long-range optical fiber, Eve cannot acquire any information about the phase scanning of the Alice end or change the quantum state sent by the Alice end, under the condition, the quantum state sent by the Alice end is a pairwise orthogonal quantum state, and the known phase remapping attack cannot be implemented.
Preferably, the scanning process of the Alice terminal is as follows:
s11, scanning the phase modulation voltage of a PMA (phase modulator) at the Alice end from Vmin to Vmax by step size delta V, wherein Vmin is the minimum phase modulation voltage, and Vmax is the maximum phase modulation voltage;
s12, waiting for N synchronous pulses at each voltage value Vi, accumulating the counts of the single-photon detectors to obtain a count Ci, and obtaining a group of data { Vi, Ci }, wherein a curve formed by the data group { Vi, Ci } is a single-photon interference curve of an Alice end;
s13, obtaining half-wave voltage V of the phase modulator at the Alice end according to the single-photon interference curve at the Alice endπ,aAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is applieda,0,Va,π,
The Bob end scanning process comprises the following steps:
s21, scanning phase modulation voltage of the Bob-end phase modulator PMB to V 'max from V' min by step size delta V, wherein V 'min is minimum phase modulation voltage, and V' max is maximum phase modulation voltage;
s22, waiting for M synchronous pulses at each voltage value V 'i, accumulating the counts of the single-photon detectors to obtain a count C' i, and obtaining a group of data { V 'i, C' i }, wherein a curve formed by the data group { V 'i, C' i } is a single-photon interference curve at a Bob end;
s23, obtaining half-wave voltage V of the phase modulator at the Bob end according to the single-photon interference curve at the Bob endπ,bAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is appliedb,0,Vb,π,
Preferably, Vmin to Vmax cover at least a phase range of 2 pi in said step S11; the step S21 is executed such that V 'min to V' max cover at least a phase range of 2 pi.
Preferably, the Alice end active phase compensation method is as follows:
selecting a point voltage with phase difference pi as a reference voltage V from a single photon interference curve of an Alice terminalref,aAnd then:
wherein,for the inherent phase difference of the intermediate ring caused by the length difference,is the inherent phase difference of the Alice-side interference ring,then it is a random phase drift;
the modulation voltage working point of the phase modulation of the Alice terminal is as follows:
the voltage loaded by the phase modulator at the Alice terminal is Va,iThe phase difference is:
the Bob end active phase compensation mode is as follows:
selecting a point voltage with phase difference pi as a reference voltage V from a single photon interference curve at Bob endref,bThen, then
Wherein,for the inherent phase difference of the intermediate ring caused by the length difference,is the inherent phase difference of the Bob-end interference ring,then it is a random phase drift;
the modulation voltage working point of the phase modulation at the end Bob is as follows:
the voltage applied to the phase modulator at Bob end is Vb,jThe phase difference is:
the invention also provides a compensation device for realizing the method, which is used for realizing automatic compensation, reducing the time and complexity of phase scanning and realizing the independent scanning of Alice and Bob ends to avoid phase remapping attack or side channel attack.
The specific implementation scheme is as follows:
a device applied to an active phase compensation method of combined scanning comprises an Alice end and a Bob end connected with the Alice end, wherein an intermediate ring is added to the Alice end and is an MZ interference ring or an FM interference ring, the intermediate ring is used for interfering with the Alice end and the Bob end respectively, interference curves of the Alice end and the Bob end are obtained through scanning respectively, accordingly, phase drift parameters of a phase modulator are obtained, and then active phase compensation is carried out on the Alice end and the Bob end respectively.
Preferably, the jointly scanned active phase compensation device is based on a dual MZ system, the intermediate ring is an MZ interference ring,
the Alice end comprises a first laser, a second laser, a phase modulator PMA, a delay ring DL1, an isolator ISO1, an isolator ISO2, couplers C1-C2, a single-photon detector SPD3 and an intermediate ring; the intermediate ring comprises couplers C3, C4 and a delay ring DL 3;
the first laser is respectively connected with a phase modulator PMA and a delay ring DL1 through a coupler C1, the phase modulator PMA and the delay ring DL1 are connected in parallel, the phase modulator PMA and the delay ring DL1 are respectively connected with two input ends of a coupler C2, one output end of the coupler C2 is connected with one input end of a coupler C3, the other output end of the coupler C2 is connected with the input end of an isolator ISO1, the output end of the isolator ISO1 is connected with one output end of the coupler C3, the coupler C3 is connected with the coupler C4 through an MZ interference ring, one output end of the coupler C4 is connected with a single photon detector SPD3, one input end of the coupler C4 is connected with the output end of the isolator ISO2, and the second laser is connected with the input end of the ISO 2;
the Bob end comprises a phase modulator PMB, a delay ring DL2, couplers C5 and C6, single-photon detectors SPD1 and SPD2, an output end of the coupler C5 is connected with an input end of the coupler C6 through the phase modulator PMB, and an output end of the coupler C6 is connected with the single-photon detector SPD 1; the other output end of the coupler C5 is connected with the other input end of the coupler C6 through a delay loop DL2, and the other output end of the coupler C6 is connected with the single-photon detector SPD 2;
the Alice end is connected with the Bob end through a long-range optical fiber; the long-range optical fiber is connected with the output end of the isolator ISO 1.
The scanning process of the Alice terminal is as follows: the optical pulse emitted by the first laser is divided into two pulses by the coupler C1, one short circuit enters the coupler C2 through the phase modulator PMA, the other short circuit enters the coupler C2 through the delay ring DL1, the two long circuits enter the coupler C2, the two long circuits enter the coupler C3 in tandem, the two long circuits pass the coupler C3 and then are divided into 4 pulses, and the pulses respectively pass through the long-arm optical fiber and the short-arm optical fiber of the intermediate ring. The pulse of the first-arm optical fiber and the pulse of the second-arm optical fiber interfere with the pulse of the first-arm optical fiber and the pulse of the second-arm optical fiber at C4, and a single-photon interference curve is detected by a photon detector SPD 3.
Bob end scanning process: the optical pulse emitted by the second laser is divided into two pulses by a coupler C4, enters a C3 after passing through an intermediate ring, enters a long-range optical fiber in tandem, reaches the Bob end, is divided into 4 pulses by a coupler C5, is interfered at a coupler C6 after passing through a phase modulator PMB and a delay ring DL2 respectively, and is detected by an SPD1 and an SPD 2.
Preferably, the active phase compensation device of the joint scan is based on a dual FM system, the intermediate ring is an FM interference ring,
the Alice end comprises Faraday mirrors FM 1-FM 2, a first laser, a second laser, a phase modulator PMA, a coupler BS1, a circulator CIR 1-CIR 2, a delay ring DL1, a single-photon detector SPD and an intermediate ring, wherein the intermediate ring comprises a delay ring DL2, a coupler BS2 and Faraday mirrors FM 3-FM 4;
laser emitted by a first laser enters a coupler BS1 and is divided into two pulses, the two pulses respectively travel through a long arm and a short arm, the two pulses are reflected by a Faraday mirror FM1 and a Faraday mirror FM2 to the other end of the coupler BS1 and enter a first port of a circulator CIR1, the two pulses enter a middle ring through a second port of a circulator CIR1, and the two pulses are divided into 4 pulses after passing through a coupler BS2 and are respectively reflected by a Faraday mirror FM3 and a Faraday mirror FM4 to a coupler BS 2; two pulses of a long arm and a short arm are interfered at a coupler BS2, and a single-photon interference curve is detected by a single-photon detector SPD; so as to obtain the phase drift parameter of the Alice terminal
The Bob end comprises Faraday mirrors FM 5-FM 6, a phase modulator PMB, a coupler BS3, a delay ring DL3, a photon detector SPD1 and a circulator CIR3, laser emitted by the second laser enters the coupler BS2 through the circulator CIR2 and is divided into two pulses which respectively go away from a long arm and a short arm of the coupler BS2, and then the two pulses are reflected back to the coupler BS2 by the Faraday mirror FM3 and the Faraday mirror FM4 to enter a second port of the circulator CIR1 in a front-and-back manner and enter a long-range optical fiber through a tail end port; the long-range optical fiber enters a first port of a Bob end circulator CIR3, enters a coupler BS3 through a second port and is divided into 4 pulses, and a Faraday mirror FM5 and a Faraday mirror FM6 are respectively reflected back to the coupler BS 3; similarly, two pulses of the long arm and the short arm are interfered at the coupler BS3, a single-photon interference curve is obtained by SPD1, and phase drift parameters of the Bob end are obtained.
Preferably, the circulator is a three-port open-loop circulator, that is, the optical path is input by the first port and output by the second port, and the input by the second port and output by the third port; the end port is a third port.
Compared with the prior art, the invention has the beneficial effects that: the invention carries out active phase compensation by adding an interference intermediate ring at the Alice end. Compared with the existing active compensation scheme, the scheme has the following improvements:
1. the Alice end and the Bob end respectively interfere with the intermediate ring to obtain working voltage points distributed by respective keys, and the phase scanning process of the Alice end is completely completed locally, so that the transmission of a phase scanning result in a public channel is avoided, Eve cannot acquire phase scanning information, and the safety of the system is improved.
2. The phase scanning process of the Alice end is completely completed locally, photons do not pass through the long-range optical fiber in the scanning process, the phenomenon that the quantum state sent by the Alice is changed in the phase scanning process by Eve is avoided, and phase remapping attack and possible deformation of the phase remapping attack are prevented.
3. Alice and Bob only need to scan once respectively to obtain respective interference curves to obtain respective voltage working points, so that the scanning complexity is reduced, the scanning time is shortened, and the duty ratio of information is increased.
4. The premise of scanning only once is that the modulation curve of the phase modulator is assumed to be linear, and in a real device, the modulation curve is not linear. The problem of non-linearity of the modulation curve of the phase modulator can be considered in two aspects. On one hand, the problem of non-linearity of a modulation curve of a phase modulator is solved, and although the modulation curve cannot be completely linear in an actual device, the linearity of the lithium niobate phase modulator which is commonly used at present can meet the requirement of QKD (quantum key distribution), and the influence on key distribution is small. Another aspect is the problem with the variation of the half-wave voltage of the phase modulator over time. Through experimental observation, the half-wave voltage of the phase modulator can change after being used for a long time, and the accuracy of the loading phase is influenced. In the scheme, the half-wave voltage of the phase modulator at the end of Alice and Bob is obtained through the scanning result, and the half-wave voltage of the phase modulator is reflected in real time, so that the problem of the change of the half-wave voltage is well solved.
Drawings
FIG. 1 is a schematic diagram of the scanning of Alice side in a dual MZ system according to the present invention.
FIG. 2 is a schematic diagram of a Bob end structure applied to a dual MZ system.
FIG. 3 is a schematic diagram of an Alice terminal structure applied to an FM system according to the present invention.
Fig. 4 is a schematic structural diagram of Bob end of the FM system.
Detailed Description
The present invention will be further described with reference to the accompanying drawings, but the embodiments of the present invention are not limited thereto.
Example one
Fig. 1 and 2 are schematic diagrams illustrating scanning of an Alice terminal when the present invention is applied to a dual MZ system; and adding an intermediate ring at the Alice end, interfering with the rings at the Alice end and the Bob end respectively to obtain phase drift parameters of the phase modulators at the Alice end and the Bob end, and then compensating respectively. The Alice end comprises a first laser, a second laser, a phase modulator PMA, a delay ring DL1, an isolator ISO1, an isolator ISO2, couplers C1-C2, a single-photon detector SPD3 and an intermediate ring; the intermediate ring comprises couplers C3, C4 and a delay ring DL 3;
the first laser is respectively connected with a phase modulator PMA and a delay ring DL1 through a coupler C1, the phase modulator PMA and the delay ring DL1 are connected in parallel, the phase modulator PMA and the delay ring DL1 are respectively connected with two input ends of a coupler C2, one output end of the coupler C2 is connected with one input end of a coupler C3, the other output end of the coupler C2 is connected with the input end of an isolator ISO1, the output end of the isolator ISO1 is connected with one output end of the coupler C3, the coupler C3 is connected with the coupler C4 through an MZ interference ring, one output end of the coupler C4 is connected with a single photon detector SPD3, one input end of the coupler C4 is connected with the output end of the isolator ISO2, and the second laser is connected with the input end of the ISO 2;
the Bob end comprises a phase modulator PMB, a delay ring DL2, couplers C5 and C6, single-photon detectors SPD1 and SPD2, an output end of the coupler C5 is connected with an input end of the coupler C6 through the phase modulator PMB, and an output end of the coupler C6 is connected with the single-photon detector SPD 1; the other output end of the coupler C5 is connected with the other input end of the coupler C6 through a delay loop DL2, and the other output end of the coupler C6 is connected with the single-photon detector SPD 2;
the Alice end is connected with the Bob end through a long-range optical fiber; the long-range optical fiber is connected with the output end of the isolator ISO 1.
Assuming that the phase difference of the intermediate ring is constant over a certain time range, Alice and Bob only need to do phase scanning with the intermediate ring, respectively. The parameters of the phase drift are respectively determined, and the phase difference during interference is determined by the phase difference loaded by the phase modulators at Alice and Bob. Therefore, the phase scanning process of the Alice end is completely completed locally, the long-range optical fiber is not passed, Eve cannot acquire any information about the phase scanning of the Alice end or change the quantum state sent by the Alice end, under the condition, the quantum state sent by the Alice end is pairwise orthogonal quantum state, and the known phase remapping attack cannot be implemented.
In the scheme of the embodiment, the scanning processes of Alice and Bob are performed in closely spaced time, and the result obtained by the scheme is not the phase drift of every two rings but the working point of key distribution, so that the result obtained by scanning is independent of the phase drift of the third ring.
The following describes the scanning and compensation process of the MZ system as an example.
First, scanning process
The scanning process of the Alice terminal is as follows:
1. scanning the phase modulation voltage of the phase modulator PMA at the Alice end from Vmin to Vmax by step size delta V, wherein the phase range of 2 pi at least is covered from Vmin to Vmax.
2. And waiting for N synchronous pulses at each voltage value Vi, accumulating the counts of the single-photon detectors to obtain a count Ci, and obtaining a group of data { Vi, Ci }, wherein the curve is a single-photon interference curve.
3. The half-wave voltage V of the phase modulator at the Alice end can be obtained according to the curveπ,aAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is applieda,0,Va,π,
The scanning process at the Bob end is similar to that at the Alice end, except that when Bob scans, light emitted from a laser2 at the Alice end enters the long-range optical fiber after passing through the intermediate ring, and then interferes at the Bob end. Obtaining the interference curve of the Bob terminal after the steps of 1, 2 and 3, and obtaining the half-wave voltage V of the phase modulator at the Bob terminalπ,bAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is appliedb,0,Vb,π,
Second, phase drift compensation
1. Active phase compensation of Alice terminal
The interference curve of the single photon can be obtained in both scanning processes, taking the scanning of the Alice end as an example. In the single photon interference curve, the difference between the voltage corresponding to the maximum counting point and the voltage corresponding to the minimum counting point is the half-wave voltage V of the compensated Alice-end phase modulatorπ,aSelecting a point voltage with a phase difference of pi as a reference voltage Vref,aThen the following holds:
wherein,for the inherent phase difference of the intermediate ring caused by the length difference,is the inherent phase difference of the Alice-side interference ring,then there is a random phase drift.
The modulation voltage working point of the phase modulation of the Alice terminal is as follows:
the voltage loaded by the phase modulator at the Alice terminal is Va,iThe phase difference is:
2. bob-end active phase compensation
The point voltage with the phase difference of pi is also selected as the reference voltage Vref,bThen, then
In the same way, we can derive the modulation voltage operating point of the phase modulator at Bob:
the voltage applied to the phase modulator at Bob end is Vb,jThe phase difference is:
when the inherent phase difference of the intermediate ring is assumed to be kept constant within a certain time range, and the inherent phase difference of the Alice and Bob end interference rings is equal, the phase drift is compensated.
Example two
As shown in fig. 3 and 4, the Alice terminal comprises faraday mirrors FM 1-FM 2, first and second lasers, a phase modulator PMA, couplers BS 1-BS 2, circulators CIR 1-CIR 2, a delay loop DL1, a single photon detector SPD and an intermediate loop, wherein the intermediate loop comprises a delay loop DL2 and faraday mirrors FM 3-FM 4; laser emitted by a first laser enters a coupler BS1 and is divided into two pulses, the two pulses respectively travel through a long arm and a short arm, the two pulses are reflected by a Faraday mirror FM1 and a Faraday mirror FM2 to the other end of the coupler BS1 and enter a first port of a circulator CIR1, the two pulses enter a middle ring through a second port of a circulator CIR1, and the two pulses are divided into 4 pulses after passing through a coupler BS2 and are respectively reflected by a Faraday mirror FM3 and a Faraday mirror FM4 to a coupler BS 2; two pulses of a long arm and a short arm are interfered at a coupler BS2, and a single-photon interference curve is detected by a single-photon detector SPD; so as to obtain the phase drift parameter of the Alice terminal
The Bob end comprises Faraday mirrors FM 5-FM 6, a phase modulator PMB, a coupler BS3, a delay ring DL3, a photon detector SPD1, a SPD2 and a circulator CIR3, laser emitted by the second laser enters the coupler BS2 through the circulator CIR2 and is divided into two pulses which respectively go away from a long arm and a short arm of the coupler BS2, and then the two pulses are reflected back to the coupler BS2 by the Faraday mirrors FM3 and FM4 to enter a second port of the circulator CIR1 after being in tandem and enter a long-range optical fiber through a terminal port; the long-range optical fiber enters a first port of a Bob end circulator CIR3, enters a coupler BS3 through a second port and is divided into 4 pulses, and a Faraday mirror FM5 and a Faraday mirror FM6 are respectively reflected back to the coupler BS 3; similarly, two pulses of the long arm and the short arm are interfered at the coupler BS3, and a single-photon interference curve is obtained by SPD1 or SPD2 to obtain phase drift parameters of Bob end.
In this embodiment, the circulator is a three-port open-loop circulator, that is, the optical path is input by the first port and output by the second port, and the input by the second port and output by the third port; the end port is a third port.
The scanning and compensating process in the FM system of the invention is consistent with the MZ system.
The joint scanning active phase compensation scheme adopted by the invention has the following advantages:
1. the phase drift parameters can be obtained by respectively scanning Alice and Bob once, so that the scanning time is shortened, the scanning complexity is reduced, and the information duty ratio of the system is improved.
2. In both single-phase and four-phase scanning methods, Bob needs to inform Alice of the phase scanning result through a classical channel, which gives Eve the possibility to obtain phase information from it, resulting in an opportunity to influence or change the phase compensation result. In the scheme, the scanning results of Alice and Bob are completely obtained respectively, the classical information transmission between the Alice and Bob does not relate to the phase scanning result, and Eve cannot acquire the relevant information of the phase scanning from a public channel, so that the safety of the system is improved.
3. The scanning of the Alice side is completely completed locally, and an eavesdropper cannot acquire any information about the phase scanning of the Alice side or change the quantum state sent by Alice. Therefore, 4 quantum states sent by Alice end are orthogonal pairwise, which completely accords with the standard of BB84 protocol, the known phase remapping attack and possible deformation thereof lose the physical basis, and therefore the implementation can not be realized, and the safety of the system is improved.
The above-described embodiments of the present invention do not limit the scope of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and scope of the present invention shall be included in the protection scope of the claims of the present invention.
Claims (8)
1. A scanning-combined active phase compensation method is characterized in that an intermediate ring is added at an Alice end and is an MZ interference ring or an FM interference ring, the intermediate ring interferes with rings at the Alice end and a Bob end respectively, interference curves at the Alice end and the Bob end are obtained through scanning, so that phase drift parameters of a phase modulator are obtained, and then active phase compensation is carried out on the Alice end and the Bob end respectively.
2. The method of active phase compensation for joint scanning of claim 1,
the scanning process of the Alice terminal is as follows:
s11, scanning the phase modulation voltage of a PMA (phase modulator) at the Alice end from Vmin to Vmax by step size delta V, wherein Vmin is the minimum phase modulation voltage, and Vmax is the maximum phase modulation voltage;
s12, waiting for N synchronous pulses at each voltage value Vi, accumulating the counts of the single-photon detectors to obtain a count Ci, and obtaining a group of data { Vi, Ci }, wherein a curve formed by the data group { Vi, Ci } is a single-photon interference curve of an Alice end;
s13, obtaining half-wave voltage V of the phase modulator at the Alice end according to the single-photon interference curve at the Alice endπ,aAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is applieda,0,Va,π,
The Bob end scanning process comprises the following steps:
s21, scanning phase modulation voltage of the Bob-end phase modulator PMB to V 'max from V' min by step size delta V, wherein V 'min is minimum phase modulation voltage, and V' max is maximum phase modulation voltage;
s22, waiting for M synchronous pulses at each voltage value V 'i, accumulating the counts of the single-photon detectors to obtain a count C' i, and obtaining a group of data { V 'i, C' i }, wherein a curve formed by the data group { V 'i, C' i } is a single-photon interference curve at a Bob end;
s23, obtaining half-wave voltage V of the phase modulator at the Bob end according to the single-photon interference curve at the Bob endπ,bAnd a voltage V when a phase of 0, pi/2, pi, 3 pi/2 is appliedb,0,Vb,π,
3. The active phase compensation method of joint scan according to claim 2, wherein Vmin to Vmax in step S11 covers at least a phase range of 2 pi; the step S21 is executed such that V 'min to V' max cover at least a phase range of 2 pi.
4. Active phase compensation method of joint scanning according to claim 2 or 3,
the active phase compensation mode of the Alice terminal is as follows:
selecting a point voltage with phase difference pi as a reference voltage V from a single photon interference curve of an Alice terminalref,aAnd then:
wherein,for the inherent phase difference of the intermediate ring caused by the length difference,is the inherent phase difference of the Alice-side interference ring,then it is a random phase drift;
the modulation voltage working point of the phase modulation of the Alice terminal is as follows:
the voltage loaded by the phase modulator at the Alice terminal is Va,iThe phase difference is:
wherein the value of i is 0, or a combination thereof,1，2，3；
the Bob end active phase compensation mode is as follows:
selecting a point voltage with phase difference pi as a reference voltage V from a single photon interference curve at Bob endref,bThen, then
Wherein,for the inherent phase difference of the intermediate ring caused by the length difference,is the inherent phase difference of the Bob-end interference ring,then it is a random phase drift;
the modulation voltage working point of the phase modulation at the end Bob is as follows:
the voltage applied to the phase modulator at Bob end is Vb,jThe phase difference is:
wherein j is 0, 1, 2, 3.
5. A device applied to an active phase compensation method of joint scanning comprises an Alice end and a Bob end connected with the Alice end, and is characterized in that an intermediate ring is added to the Alice end, the intermediate ring is an MZ interference ring or an FM interference ring, the intermediate ring is used for interfering with the Alice end and the Bob end respectively, interference curves of the Alice end and the Bob end are obtained through scanning respectively, phase drift parameters of a phase modulator are obtained, and then the Alice end and the Bob end are subjected to active phase compensation respectively.
6. The apparatus of claim 5, wherein the jointly scanned active phase compensation apparatus is based on a dual MZ system, wherein the intermediate ring is a MZ interference ring,
the Alice end comprises a first laser, a second laser, a phase modulator PMA, a delay ring DL1, an isolator ISO1, an isolator ISO2, couplers C1-C2, a single-photon detector SPD3 and an intermediate ring; the intermediate ring comprises couplers C3, C4 and a delay ring DL 3;
the first laser is respectively connected with a phase modulator PMA and a delay ring DL1 through a coupler C1, the phase modulator PMA and the delay ring DL1 are connected in parallel, the phase modulator PMA and the delay ring DL1 are respectively connected with two input ends of a coupler C2, one output end of the coupler C2 is connected with one input end of a coupler C3, the other output end of the coupler C2 is connected with the input end of an isolator ISO1, the output end of the isolator ISO1 is connected with one output end of the coupler C3, the coupler C3 is connected with the coupler C4 through an MZ interference ring, one output end of the coupler C4 is connected with a single photon detector SPD3, one input end of the coupler C4 is connected with the output end of the isolator ISO2, and the second laser is connected with the input end of the ISO 2;
the Bob end comprises a phase modulator PMB, a delay ring DL2, couplers C5 and C6, single-photon detectors SPD1 and SPD2, an output end of the coupler C5 is connected with an input end of the coupler C6 through the phase modulator PMB, and an output end of the coupler C6 is connected with the single-photon detector SPD 1; the other output end of the coupler C5 is connected with the other input end of the coupler C6 through a delay loop DL2, and the other output end of the coupler C6 is connected with the single-photon detector SPD 2;
the Alice end is connected with the Bob end through a long-range optical fiber; the long-range optical fiber is connected with the output end of the isolator ISO 1.
7. The apparatus of claim 5, wherein the jointly scanned active phase compensation apparatus is based on a dual FM system, the intermediate ring is an FM interference ring,
the Alice end comprises Faraday mirrors FM 1-FM 2, a first laser, a second laser, a phase modulator PMA, a coupler BS1, a circulator CIR 1-CIR 2, a delay ring DL1, a single-photon detector SPD and an intermediate ring, wherein the intermediate ring comprises a delay ring DL2, a coupler BS2 and Faraday mirrors FM 3-FM 4;
laser emitted by the first laser enters the coupler BS1 and is divided into two pulses, the two pulses respectively travel through a long arm and a short arm, the two pulses are reflected by a Faraday mirror FM1 and a Faraday mirror FM2 to the other end of the coupler BS1 and enter a first port of a circulator CIR1, the two pulses enter a middle ring through a second port of a circulator CIR1, and the two pulses are divided into 4 pulses after passing through a coupler BS2 and are respectively reflected by a Faraday mirror FM3 and a Faraday mirror FM4 to the coupler BS 2; two pulses of a long arm and a short arm are interfered at a coupler BS2, and a single-photon interference curve is detected by a single-photon detector SPD;
the Bob end comprises Faraday mirrors FM 5-FM 6, a phase modulator PMB, a coupler BS3, a delay ring DL3, a photon detector SPD1 and a circulator CIR3, laser emitted by the second laser enters the coupler BS2 through the circulator CIR2 and is divided into two pulses which respectively go away from a long arm and a short arm of the coupler BS2, and then the two pulses are reflected back to the coupler BS2 by the Faraday mirror FM3 and the Faraday mirror FM4 to enter a second port of the circulator CIR1 in a front-and-back manner and enter a long-range optical fiber through a tail end port; the long-range optical fiber enters a first port of a Bob end circulator CIR3, enters a coupler BS3 through a second port and is divided into 4 pulses, and a Faraday mirror FM5 and a Faraday mirror FM6 are respectively reflected back to the coupler BS 3; similarly, two pulses of the long arm followed by the short arm and the short arm followed by the short arm interfere at the coupler BS3, and a single-photon interference curve is obtained by the SPD 1.
8. The apparatus of claim 7, wherein the circulator is a three-port open-loop circulator, i.e., an optical path is routed from a first port input to a second port output, and from the second port input to a third port output; the end port is a third port.
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| CN105959113B (en) * | 2016-07-06 | 2018-11-30 | 洛阳师范学院 | For preventing the quantum key distribution method of detector side channel attack |
| CN108242996B (en) * | 2016-12-23 | 2020-11-17 | 华为技术有限公司 | Quantum key distribution method and device |
| CN106656491B (en) * | 2016-12-30 | 2019-08-09 | 北京信息科学技术研究院 | The compensation method of half-wave voltage of phase modulator in a kind of quantum key dispatching system |
| CN107631814B (en) * | 2017-09-14 | 2020-09-01 | 电子科技大学 | Optical self-coherent sensing optical path structure, frequency shift change detection method and sensing device |
| CN108540284B (en) * | 2018-06-01 | 2020-11-20 | 北京大学 | Continuous variable quantum key distribution post-processing heterodyne detection phase compensation method |
| CN112653521B (en) * | 2019-10-11 | 2022-08-19 | 科大国盾量子技术股份有限公司 | Phase encoding QKD system and phase compensation device and method thereof |
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