High-speed time-phase encoding device, method and quantum communication system

Abstract

The application provides a high-speed time-phase encoding device, a method and a quantum communication system. The device comprises an unequal-arm interferometer, an interferometer, an optical transmission unit, a first phase modulator and a first driver. The unequal-arm interferometer processes a light beam based on a first optical coupler, a second optical coupler, a first transmission light path and a second transmission light path. The interferometer splits an input light pulse into two sub-light pulses based on the second optical coupler and a third transmission light path. The first phase modulator receives a modulation signal applied by the first driver, and phase-modulates the two sub-light pulses to form a phase difference between the two sub-light pulses. The application meets the requirement of encoding quantum states according to various quantum communication protocols, and can prepare two-group or three-group time-phase quantum states.

Description

Technical Field

[0001] The present invention relates to the field of quantum communication and optical quantum encoding and decoding technology, and in particular to a high-speed time phase encoding device, method and quantum communication system. Background Art

[0002] Quantum communication is an important branch of quantum information science. Quantum communication is a communication technology that uses quantum bits as carriers to interact with information. It can break through the limits of classical information technology in terms of ensuring information security, and therefore has high application value in many fields.

[0003] The physical implementation of quantum communication systems, such as quantum key distribution and direct quantum communication, requires encoding and decoding quantum states. Quantum communication systems using different protocols have different requirements for quantum state encoding and decoding. A key challenge in quantum communication applications is how to integrate multiple quantum communication protocols into a single optical quantum encoding and decoding device, flexibly addressing the requirements for multiple quantum state encoding and decoding.

[0004] To accommodate the needs of various communication protocols, the encoding device must be capable of encoding three base six states, generating corresponding time-phase coded quantum states based on the protocol requirements. Time-phase encoding, which employs both time and phase basis vectors, offers advantages such as robustness to environmental disturbances and efficient coding. It has gained significant attention in the industry and has become a key coding method for quantum communications.

[0005] Therefore, how to achieve high-speed and stable time-phase quantum state encoding that is compatible with multiple protocols is an unresolved problem in quantum communication applications. Summary of the Invention

[0006] The present application provides a high-speed time phase encoding device, method and quantum communication system to solve the technical problems mentioned in the prior art.

[0007] According to a first aspect of the present application, a high-speed temporal phase encoding device is provided, comprising: an unequal-arm interferometer, an interferometer, an optical transmission unit, a first phase modulator, and a first driver.

[0008] The unequal-arm interferometer includes: a first optical coupler, a second optical coupler, a first transmission optical path, and a second transmission optical path having an optical path length unequal to that of the first transmission optical path; the first optical coupler includes three ports, namely, port A, port B, and port C; the second optical coupler includes four ports, namely, port D, port E, port F, and port G; the first transmission optical path connects port B of the first optical coupler and port D of the second optical coupler; the second transmission optical path connects port C of the first optical coupler and port E of the second optical coupler;

[0009] The interferometer includes: a second optical coupler and a third transmission optical path, wherein port G and port F of the second optical coupler are connected via the third transmission optical path, and the second optical coupler is used to split the optical pulse input to the interferometer into two sub-optical pulses;

[0010] The first phase modulator is disposed on the third transmission optical path. The first phase modulator includes three ports, namely, port L, port M, and electrical port N. Port L and port M are, respectively, a forward input optical port and a reverse input optical port of the first phase modulator. The electrical port N is connected to the first driver and is configured to receive a modulation signal applied by the first driver. After being applied with a high-frequency modulation signal having a frequency higher than a specified threshold, the first phase modulator enters a non-reciprocal state. A ratio of a modulation efficiency of one of the two optical sub-pulses inputted from the forward input optical port to a modulation efficiency of the one of the optical sub-pulses inputted from the reverse input optical port is greater than a preset threshold.

[0011] The optical transmission unit is arranged on the first transmission optical path. One of the optical transmission unit and the first optical coupler serves as the optical input end of the high-speed time phase encoding device, and the other serves as the optical output end of the high-speed time phase encoding device.

[0012] In some implementations, the optical transmission unit includes three ports, namely port X, port Y, and port Z; port Z and port Y of the optical transmission unit are respectively connected to the first optical coupler port B and the second optical coupler port D through the first transmission optical path;

[0013] When the optical transmission unit serves as the optical input end of the high-speed time phase encoding device, the optical signal input from port X of the optical transmission unit is output from port Y after passing through the optical transmission unit, and the optical signal input from port Y of the optical transmission unit is output from port Z after passing through the optical transmission unit; when the optical transmission unit serves as the optical output end of the high-speed time phase encoding device, the optical signal input from port Z of the optical transmission unit is output from port Y after passing through the optical transmission unit, and the optical signal input from port Y of the optical transmission unit is output from port X after passing through the optical transmission unit.

[0014] In some implementations, when the optical transmission unit port X is the optical output port of the high-speed time phase encoding device, and the first optical coupler port A is the optical input port of the high-speed time phase encoding device,

[0015] The first optical coupler splits an optical pulse input through port A into two optical pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is input into the second optical coupler through the first transmission optical route via the second optical coupler port D, and is output from the second optical coupler port G and port F; the second optical pulse is input into the second optical coupler through the second transmission optical route via the second optical coupler port E, and is output from the second optical coupler port G and port F; the first reflected sub-optical pulse output from the first optical pulse through the second optical coupler port G and the second reflected sub-optical pulse output from the second optical coupler port G and the second optical pulse are output from the second optical coupler port F. The second-path transmitted sub-optical pulse outputted from the coupler port G constitutes a third-path optical pulse, which is transmitted counterclockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port F; the first-path transmitted sub-optical pulse outputted from the first-path optical pulse through the second optical coupler port F and the second-path reflected sub-optical pulse outputted from the second optical coupler port F constitute a fourth-path optical pulse, which is transmitted clockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port G; the third-path optical pulse and the fourth-path optical pulse both contain optical pulses of two consecutive time slots within one pulse cycle;

[0016] The first phase modulator performs phase modulation on the third path optical pulse input from the forward input optical port, or performs phase modulation on one of the two time slots of the third path optical pulse;

[0017] The second optical coupler combines the third optical pulse and the fourth optical pulse after passing through the first phase modulator, and outputs them from the second optical coupler port D to the optical transmission unit port Y, and then outputs them through the optical transmission unit port X.

[0018] In some implementations, when the optical transmission unit port X is the optical input port of the high-speed time phase encoding device and the first optical coupler port A is the optical output port of the high-speed time phase encoding device,

[0019] An optical pulse is input through the optical transmission unit port X, output from the optical transmission unit port Y to the second optical coupler port D, and split by the second optical coupler into two optical pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is output from the second optical coupler port G, transmitted counterclockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port F; the second optical pulse is output from the second optical coupler port F, transmitted clockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port G;

[0020] The first phase modulator performs phase modulation on the first path of optical pulses input from the forward input optical port;

[0021] The second optical coupler combines the first optical pulse and the second optical pulse after passing through the first phase modulator, and outputs them through port D and port E of the second optical coupler. The optical pulse output from port D is output to port Y of the optical transmission unit, and output to port B of the first optical coupler through port Z of the optical transmission unit; the optical pulse output from port E is output to port C of the first optical coupler; the two optical pulses input into the first optical coupler from ports B and C of the first optical coupler are combined and output from port A of the first optical coupler.

[0022] In some implementations, the first phase modulator modulates one of the two time slots of the third-path optical sub-pulse by 0° or 180°.

[0023] In some implementations, the two paths of sub-light pulses pass through the first phase modulator simultaneously.

[0024] In some implementations, the first phase modulator randomly modulates one of the two optical sub-pulses input from the forward input optical port by 0°, 90°, 180°, or 270°.

[0025] In some implementations, the apparatus further includes: a second phase modulator and a second driver,

[0026] The second phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator;

[0027] The second phase modulator includes three ports, namely port L', port M' and electrical port N', port L' and port M' are respectively the forward input optical port and reverse input optical port of the second phase modulator; port L' and port M' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path, or port M' and port L' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path; the electrical port N' of the second phase modulator is connected to the second driver; the modulation signal applied by the second driver is received through the electrical port N', and the second phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

[0028] In some implementations, the apparatus further includes: a third phase modulator and a third driver,

[0029] The third phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator and the second phase modulator;

[0030] The third phase modulator includes three ports, namely port L", port M", and port N", port L" and port M" are the forward input optical port and reverse input optical port of the third phase modulator, respectively. The electrical port N" of the third phase modulator is connected to the third driver and receives the modulation signal applied by the third driver through the electrical port N", and the third phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

[0031] In some implementations, the apparatus further includes: a second phase modulator and a second driver,

[0032] The second phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator;

[0033] The second phase modulator includes three ports, namely port L', port M' and electrical port N', port L' and port M' are respectively the forward input optical port and reverse input optical port of the second phase modulator; port L' and port M' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path, or port M' and port L' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path; the electrical port N' of the second phase modulator is connected to the second driver; the modulation signal applied by the second driver is received through the electrical port N', and the second phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

[0034] In some implementations, the optical transmission unit is an optical coupler or an optical circulator.

[0035] In some implementations, the apparatus further includes: an attenuator,

[0036] The attenuator is arranged in the first transmission optical path or the second transmission optical path, and is used to adjust the loss of the two arms of the unequal-arm interferometer.

[0037] In some implementations, the first transmission optical path, the second transmission optical path, and / or the third transmission optical path are polarization-maintaining optical fibers.

[0038] In some implementations, the second optical coupler port G and port F are both coupled to the slow axis of the polarization-maintaining fiber of the third transmission optical path, or are both coupled to the fast axis of the polarization-maintaining fiber of the third transmission optical path.

[0039] In some implementations, the first optical coupler and / or the second optical coupler is a polarization-maintaining fiber coupler.

[0040] According to a second aspect of the present application, a high-speed time phase encoding method is provided, which uses any of the high-speed time phase encoding devices described above to implement high-speed time phase encoding.

[0041] According to a third aspect of the present application, a quantum communication system is provided, comprising the high-speed time phase encoding device described in any one of the above items.

[0042] In summary, the high-speed time phase encoding device, method, and quantum communication system provided by this application have at least the following beneficial effects:

[0043] The high-speed time phase encoding device of the present application includes an unequal-arm interferometer, an interferometer, an optical transmission unit, a first phase modulator and a first driver, wherein the unequal-arm interferometer processes the light beam based on the first optical coupler, the second optical coupler, the first transmission optical path and the second transmission optical path; the interferometer splits the light pulse input to the interferometer into two sub-light pulses based on the second optical coupler and the third transmission optical path; the first phase modulator receives the modulation signal applied by the first driver, phase-modulates the two sub-light pulses, and forms a phase difference between the two sub-light pulses. The high-speed time phase encoding device, method and quantum communication system of the present application apply a high-frequency modulation signal to the first phase modulator arranged in the interferometer optical path structure, so that the first phase modulator has non-reciprocal phase modulation for the forward and reverse input optical pulses, so that the first phase modulator can effectively phase modulate the forward input optical pulse, but cannot effectively phase modulate the reverse input optical pulse; therefore, when the forward transmitted optical pulse and the reverse transmitted optical pulse both pass through the high-frequency modulated phase modulator, the forward transmitted optical pulse obtains phase modulation, and the reverse transmitted optical pulse does not, forming a phase difference between the two optical pulses, which can realize 10GHz or higher time phase quantum state encoding and decoding.

[0044] In addition, in the interferometer optical path, the optical paths through which the clockwise and counterclockwise optical pulses are transmitted are exactly the same, and they have a self-compensation function for environmental interference. They can compensate for the phase drift caused by the optical path and phase modulator caused by environmental changes. No temperature control measures or active phase supplementation are required, and they have the advantages of high anti-interference stability.

[0045] In addition, the present application can achieve stable modulation of two groups of basis four polarization states, and can also achieve encoding of time phase quantum states such as three groups of basis six polarization states or three groups of basis four polarization states, thereby achieving compatibility with the quantum state encoding requirements of multiple quantum communication protocols.

[0046] Therefore, the present application provides an implementation scheme for a high-speed stable time phase encoding device that is easy to implement and apply and is compatible with multiple quantum communication protocols. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without any creative work.

[0048] Figure 1 A framework diagram of a high-speed time phase encoding device provided in an embodiment of the present application;

[0049] Figure 2 A structural diagram of a first embodiment of a high-speed time phase encoding device provided in an embodiment of the present application;

[0050] Figure 3 This is a structural diagram of a second embodiment of a high-speed time phase encoding device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0051] In order to make the above and other features and advantages of the present application more clear, the present application is further described below with reference to the accompanying drawings. It should be understood that the specific embodiments given herein are for the purpose of explaining to those skilled in the art and are only exemplary and not restrictive.

[0052] In the following description, many specific details are set forth to provide a thorough understanding of the present application. However, it will be apparent to those skilled in the art that it is not necessary to adopt the specific details to practice the present application. In other cases, well-known steps or operations are not described in detail to avoid obscuring the present application.

[0053] It should be noted that the time phase encoding described in this application includes phase encoding, that is, the time phase encoding is an encoding composed of any combination of quantum states of the X phase basis, the Y phase basis, and the Z time basis.

[0054] Refer to the attached Figure 1 and attached Figure 2 As shown, the embodiment of the present application provides a first embodiment of a high-speed time phase encoding device, Figure 1 This is the framework diagram of the high-speed time phase encoding device, Figure 2 This is a structural diagram of a first embodiment of a high-speed temporal phase encoding device. The device includes: an unequal-arm interferometer 100, an interferometer 200, an optical transmission unit 203, a first phase modulator 207, and a first driver 208, all of which are connected via a transmission optical path. In some embodiments, the unequal-arm interferometer 100 includes: a first optical coupler 201, a second optical coupler 202, a first transmission optical path 204, and a second transmission optical path 205 having an optical path length unequal to that of the first transmission optical path 204. The first optical coupler 201 includes three ports, namely, port A, port B, and port C. The second optical coupler 202 includes four ports, namely, port D, port E, port F, and port G. The first transmission optical path 204 connects port B of the first optical coupler 201 and port D of the second optical coupler 202. The second transmission optical path 205 connects port C of the first optical coupler and port E of the second optical coupler 202.

[0055] In some embodiments, the interferometer 200 includes: a second optical coupler 202 and a third transmission optical path 206, wherein port G and port F of the second optical coupler 202 are connected via the third transmission optical path 206, and the second optical coupler 202 is used to split the optical pulse input to the interferometer 200 into two sub-optical pulses.

[0056] In some embodiments, the first phase modulator 207 is disposed on the third transmission optical path 206. The first phase modulator 207 includes three ports, namely, port L, port M, and electrical port N. Port L and port M are the forward input optical port and reverse input optical port of the first phase modulator 207, respectively. The electrical port N is connected to the first driver 208 and is configured to receive a modulation signal applied by the first driver 208. After being applied with a high-frequency modulation signal having a frequency greater than a specified threshold, the first phase modulator 207 enters a non-reciprocal state. The ratio of the modulation efficiency of the optical sub-pulse inputted from the forward input optical port to the modulation efficiency of the optical sub-pulse inputted from the reverse input optical port is greater than a preset threshold. The preset threshold may be 10 decibels (dB). The high-frequency modulation signal is, for example, a modulation signal of not less than 10 GHz.

[0057] For example, when a 10GHz high-frequency modulation voltage is applied to the first phase modulator, the first phase modulator can effectively phase modulate the optical pulse transmitted in the forward direction, but cannot effectively phase modulate the optical pulse transmitted in the reverse direction. The difference in modulation efficiency between the two can be more than 100 times. At this time, it can be regarded as not modulating the phase of the optical pulse transmitted in the reverse direction.

[0058] In some embodiments, the optical transmission unit 203 is disposed on the first transmission optical path 204 .

[0059] One of the optical transmission unit 203 and the first optical coupler 201 serves as an optical input end of the high-speed temporal phase encoding device, and the other serves as an optical output end of the high-speed temporal phase encoding device.

[0060] In an exemplary embodiment, the unequal-arm interferometer 100 adopts a Mach-Zehnder interferometer optical path structure, and the optical transmission unit 203 includes three ports, namely port X, port Y, and port Z; port Z and port Y of the optical transmission unit 203 are respectively connected to port B of the first optical coupler 201 and port D of the second optical coupler 202 through the first transmission optical path 204;

[0061] When the optical transmission unit 203 serves as the optical input end of the high-speed time phase encoding device, the optical signal input from port X of the optical transmission unit 203 is output from port Y after passing through the optical transmission unit 203, and the optical signal input from port Y of the optical transmission unit 203 is output from port Z after passing through the optical transmission unit 203; when the optical transmission unit 203 serves as the optical output end of the high-speed time phase encoding device, the optical signal input from port Z of the optical transmission unit 203 is output from port Y after passing through the optical transmission unit 203, and the optical signal input from port Y of the optical transmission unit 203 is output from port X after passing through the optical transmission unit 203.

[0062] In an exemplary embodiment, when port X of the optical transmission unit 203 is the optical output port of the high-speed time phase encoding device and port A of the first optical coupler 201 is the optical input port of the high-speed time phase encoding device, the first optical coupler 201 splits an optical pulse input through port A into two optical sub-pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is input to the second optical coupler 202 through port D of the second optical coupler via the first transmission optical path 204, and is output from ports G and F of the second optical coupler 202; the second optical pulse is input to the second optical coupler 202 through port E of the second optical coupler 202 via the second transmission optical path 205, and is output from ports G and F of the second optical coupler 202; the first reflected sub-optical pulse of the first optical pulse output through port G of the second optical coupler 202 and the second transmitted sub-optical pulse of the second optical pulse output through port G of the second optical coupler 202 form a third optical pulse, which is transmitted along the third transmission optical path 206. After passing through the first phase modulator 207 in a counterclockwise direction, the optical pulse is transmitted to port F of the second optical coupler 202. The first transmitted sub-optical pulse of the first optical pulse output from port F of the second optical coupler 202 and the second reflected sub-optical pulse of the second optical pulse output from port F of the second optical coupler 202 form a fourth optical pulse, which is then transmitted clockwise along the third transmission optical path 206 through the first phase modulator 207 to port G of the second optical coupler 202. Both the third and fourth optical pulses contain optical pulses of two consecutive time slots within a pulse cycle. The first phase modulator 207 phase-modulates the third optical pulse input from the forward input optical port, or phase-modulates one of the two time slots of the third optical pulse. The second optical coupler 202 combines the third and fourth optical pulses after passing through the first phase modulator 207, and outputs the combined optical pulses from port D of the second optical coupler 202 to port Y of the optical transmission unit 203, and then outputs the combined pulses from port X of the optical transmission unit 203.

[0063] In some implementations, the first phase modulator 207 modulates one of the two time slots of the third path optical sub-pulse by 0° or 180°.

[0064] In an exemplary embodiment, when port X of the optical transmission unit 203 is the optical input port of the high-speed time phase encoding device and port A of the first optical coupler 201 is the optical output port of the high-speed time phase encoding device, an optical pulse is input through port X of the optical transmission unit 203, output from port Y of the optical transmission unit 203 to port D of the second optical coupler 202, and split by the second optical coupler 202 into two optical pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is output from port G of the second optical coupler 202, transmitted counterclockwise along the third transmission optical path 206 through the first phase modulator 207, and transmitted to port F of the second optical coupler 202; the second optical pulse is output from port F of the second optical coupler 202, transmitted clockwise along the third transmission optical path 206 through the first phase modulator 207, and transmitted to port G of the second optical coupler 202; the first phase modulator 207 modulates the first optical pulse input from the forward input optical port. The optical sub-pulses are phase modulated; the second optical coupler 202 combines the first optical pulse and the second optical pulse after passing through the first phase modulator 207, and outputs them through port D and port E of the second optical coupler 202. The optical pulse output from port D (an optical pulse formed by the interference of the portion of the first optical pulse transmitted by the second optical coupler 202 and the portion of the second optical pulse reflected by the second optical coupler 202) is output to port Y of the optical transmission unit 203, and is output to port B of the first optical coupler through port Z of the optical transmission unit 203; the optical pulse output from port E (an optical pulse formed by the interference of the portion of the first optical pulse reflected by the second optical coupler 202 and the portion of the second optical pulse transmitted by the second optical coupler 202) is output to port C of the first optical coupler 201; the two optical pulses input to the first optical coupler 201 through ports B and C of the first optical coupler 201 are combined and output from port A of the first optical coupler 201.

[0065] In one exemplary embodiment, after a high-frequency adjustment signal is applied to the first phase modulator, the first phase modulator can randomly modulate one of the two optical sub-pulses input from the forward input optical port by 0°, 90°, 180°, or 270° by randomly modulating the magnitude of the high-frequency modulation signal. In this case, the high-speed temporal phase encoding device can generate two time-encoded quantum states of the time basis Z and two phase-encoded quantum states of the phase basis Y. Furthermore, if one of the two time slots of the third optical pulse is randomly modulated by 0° or 180°, the high-speed temporal phase encoding device can generate two phase-encoded quantum states of the phase basis X.

[0066] In some embodiments, as Figure 3As shown, the device further includes: a second phase modulator 209 and a second driver 210. The second phase modulator 209 is arranged on the third transmission optical path 206 and is connected in series with the first phase modulator 207. The second phase modulator 209 includes three ports, namely, port L', port M' and electrical port N'. Port L' and port M' are respectively the forward input optical port and the reverse input optical port of the second phase modulator 209. Port L' and port M' are respectively connected to port F of the second optical coupler 202 and port M of the first phase modulator 207 through the third transmission optical path 206. The second phase modulator 209 is connected to the second optical coupler 202, or the port M' and the port L' are respectively connected to the port F of the second optical coupler 202 and the port M of the first phase modulator 207 through the third transmission optical path 206; the electrical port N' of the second phase modulator 209 is connected to the second driver 210; the modulation signal applied by the second driver 210 is received through the electrical port N', and the second phase modulator 209 is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold. By connecting the first phase modulator 207 and the second phase modulator 209 in series and performing combined modulation on the two-path optical pulses, the following effects can be achieved: when it is necessary to modulate two groups of four quantum states, the two phase modulators are combined for modulation, and each phase modulator can only modulate two phases, thereby reducing the difficulty of driving circuit design by digital modulation; when it is necessary to modulate three groups of six quantum states (for example, when port A of the first optical coupler 201 is used as the optical input port of the device), the two phase modulators are combined for modulation, which can reduce the number of phases modulated by a single phase modulator, reduce the difficulty of driving circuit design, and make it easier to achieve high-speed modulation.

[0067] In an exemplary embodiment, the two paths of sub-light pulses pass through the first phase modulator 207 or the second phase modulator 209 simultaneously.

[0068] In general, according to the different light beam input ports and output ports of the high-speed time phase encoding and decoding device of the present application, there can be two configuration methods: the first configuration method is to configure port X of the optical transmission unit 203 as the output port, and configure port A of the first optical coupler 201 as the input port; the second configuration method is to configure port X of the optical transmission unit 203 as the input port, and configure port A of the first optical coupler 201 as the output port.

[0069] For example, when the first configuration is used, by applying a high-frequency modulation signal (e.g., a 10 GHz high-frequency modulation signal) to the first phase modulator 207 and the second phase modulator 209 and randomly modulating the magnitude of the high-frequency modulation signal, the first phase modulator 207 can be controlled to randomly modulate the third optical pulse by 0° or 180°, and the second phase modulator 209 can be controlled to randomly modulate the fourth optical pulse by 0° or 90°. In this case, the high-speed time-phase encoding and decoding device of the present application can generate two time-encoded quantum states of the time basis Z and two phase-encoded quantum states of the phase basis Y. In addition, by controlling the first phase modulator 207 to randomly modulate one of the two time slots of the third optical pulse by 0° or 180°, and controlling the second phase modulator 209 to randomly modulate one of the two time slots of the fourth optical pulse by 0° or 180°, the high-speed time-phase encoding and decoding device of the present application can generate two phase-encoded quantum states of the phase basis X.

[0070] For example, when the second configuration is used, by applying a high-frequency modulation signal (e.g., a 10 GHz high-frequency modulation signal) to the first phase modulator 207 and the second phase modulator 209 and randomly modulating the magnitude of the high-frequency modulation signal, the first phase modulator 207 can be controlled to randomly modulate the first optical pulse by 0° or 180°, and the second phase modulator 209 can be controlled to randomly modulate the second optical pulse by 0° or 90°. In this case, the high-speed time-phase encoding and decoding device of the present application can generate two time-encoded quantum states of the time basis Z and two phase-encoded quantum states of the phase basis Y.

[0071] When port X of the optical transmission unit 203 is the optical output port of the high-speed time phase encoding device, and port A of the first optical coupler 201 is the optical input port of the high-speed time phase encoding device, the device may further include: a third phase modulator and a third driver, the third phase modulator being arranged on the third transmission optical path and connected in series with the first phase modulator and the second phase modulator; the third phase modulator includes three ports, namely port L", port M", and port N", port L" and port M", respectively, the forward input optical port and reverse input optical port of the third phase modulator; the electrical port N' of the third phase modulator is connected to the third driver, and receives the modulation signal applied by the third driver through the electrical port N", the third phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal having a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold. By combining the first phase modulator 207, the second phase modulator 209, and the third phase modulator for modulation, each phase modulator can modulate only two phases, and realize the generation of three groups of six quantum states in a digital modulation manner, thereby reducing the difficulty of driving circuit design. For example, by applying a high-frequency modulation signal, such as a 10GHz high-frequency modulation signal, to the three phase modulators, the magnitude of the high-frequency modulation signal can be randomly modulated to control the first phase modulator 207 to randomly modulate the third path optical pulse by 0° or 180°, control the second phase modulator 209 to randomly modulate the fourth path optical pulse by 0° or 90°, and control the third phase modulator to randomly modulate one of the two time slots of the fourth path optical pulse by 0° or 180°, thereby realizing the generation of three groups of six quantum states in a digital modulation manner (the first phase modulator 207 randomly modulates the third path optical pulse by 0° or 180°, the second phase modulator 209 modulates 0°, and the third phase modulator modulates 0°, which can generate a time basis Z basis. The first phase modulator 207 randomly modulates the third path optical pulse by 0° or 180°, the second phase modulator 209 modulates the fourth path optical pulse by 90°, and the third phase modulator modulates 0°, which can generate two phase-coded quantum states of the phase basis Y basis; the first phase modulator 207 modulates one of the two time slots of the third path optical pulse by 180°, the second phase modulator 209 modulates 0°, and the third phase modulator modulates 0°, or the first phase modulator 207 modulates 0°, the second phase modulator 209 modulates 0°, and the third phase modulator modulates one of the two time slots of the fourth path optical pulse by 180°, which can generate two phase-coded quantum states of the phase basis X basis).

[0072] In some embodiments, the three phase modulators are all connected in forward series, or two of the three phase modulators are connected in forward series and the other is connected in reverse series.

[0073] It should be noted that when each phase modulator of the present application is applied with a high-frequency modulation signal with a frequency higher than a specified threshold, the phase modulator may have multiple sub-optical pulses input from the forward input optical port and sub-optical pulses input from the reverse input optical port at the same time.

[0074] In some implementations, the optical transmission unit 203 may be an optical coupler or an optical circulator.

[0075] In some embodiments, the device may further include: an attenuator, which may be provided in the first transmission optical path or the second transmission optical path, and is used to adjust the loss of the two arms of the unequal-arm interferometer.

[0076] In some embodiments, the first transmission optical path, the second transmission optical path, and / or the third transmission optical path are polarization-maintaining optical fibers.

[0077] In some embodiments, when the third transmission optical path is a polarization-maintaining fiber, the second optical coupler port G and port F are both coupled to the slow axis of the polarization-maintaining fiber, or are both coupled to the fast axis of the polarization-maintaining fiber.

[0078] In some embodiments, the first optical coupler and / or the second optical coupler is a polarization-maintaining fiber coupler.

[0079] In some embodiments, the high-speed time phase encoding device can also be used to implement high-speed time phase decoding.

[0080] The high-speed time phase encoding device of the present application can realize the encoding of time phase quantum states such as two groups of basis four polarization states, three groups of basis six polarization states, or three groups of basis four polarization states, and can meet the quantum state encoding requirements of various quantum communication protocols.

[0081] In addition, the present application adopts two phase modulators connected in series to perform combined modulation of the phase modulators, which can reduce the types of modulation phases of a single phase modulator, thereby reducing the difficulty of implementing a single phase modulator driving circuit.

[0082] In this application, the optical paths through which the clockwise and counterclockwise optical pulses are transmitted are exactly the same, and they have a self-compensation function for environmental interference. They can automatically compensate for the phase drift of the optical path and phase modulator caused by environmental changes, without the need for temperature control measures or active phase compensation, and have the advantages of high anti-interference stability.

[0083] In summary, this application provides an implementation solution for a high-speed stable time phase encoding device that is easy to implement and apply and is compatible with multiple quantum communication protocols.

[0084] The embodiment of the present application also provides a high-speed time phase encoding method, which uses the high-speed time phase encoding device of the above embodiment to implement a high-speed time phase encoding operation.

[0085] According to the present application, a quantum communication system is provided, comprising the above-mentioned high-speed time phase encoding device.

[0086] The quantum communication system can be a discrete variable quantum communication system or a continuous variable quantum communication system. It should be understood that the specific features, operations, and details described herein with respect to the apparatus of the present application can also be similarly applied to the method and system of the present application, or vice versa. In addition, each step of the method of the present application can be performed by a corresponding component or unit of the apparatus or system of the present application.

[0087] The various technical features described above can be combined arbitrarily. Although not all possible combinations of these technical features are described, any combination of these technical features should be considered to be covered by this specification as long as such combination does not conflict.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-speed time phase encoding device, characterized in that: include: an unequal-arm interferometer, an interferometer, an optical transmission unit, a first phase modulator, and a first driver, The unequal-arm interferometer includes: a first optical coupler, a second optical coupler, a first transmission optical path, and a second transmission optical path having an optical path length unequal to that of the first transmission optical path; the first optical coupler includes three ports, namely, port A, port B, and port C; the second optical coupler includes four ports, namely, port D, port E, port F, and port G; the first transmission optical path connects port B of the first optical coupler and port D of the second optical coupler; the second transmission optical path connects port C of the first optical coupler and port E of the second optical coupler; The interferometer includes: a second optical coupler and a third transmission optical path, wherein port G and port F of the second optical coupler are connected via the third transmission optical path, and the second optical coupler is used to split the optical pulse input to the interferometer into two sub-optical pulses; The first phase modulator is disposed on the third transmission optical path. The first phase modulator includes three ports, namely, port L, port M, and electrical port N. Port L and port M are, respectively, a forward input optical port and a reverse input optical port of the first phase modulator. The electrical port N is connected to the first driver and is configured to receive a modulation signal applied by the first driver. After being applied with a high-frequency modulation signal having a frequency higher than a specified threshold, the first phase modulator enters a non-reciprocal state. A ratio of a modulation efficiency of one of the two optical sub-pulses inputted from the forward input optical port to a modulation efficiency of the one of the optical sub-pulses inputted from the reverse input optical port is greater than a preset threshold. The optical transmission unit is arranged on the first transmission optical path. One of the optical transmission unit and the first optical coupler serves as the optical input end of the high-speed time phase encoding device, and the other serves as the optical output end of the high-speed time phase encoding device.

2. The device according to claim 1, characterized in that The optical transmission unit comprises three ports, namely port X, port Y and port Z; port Z and port Y of the optical transmission unit are respectively connected to the first optical coupler port B and the second optical coupler port D through the first transmission optical path; When the optical transmission unit serves as the optical input end of the high-speed time phase encoding device, the optical signal input from port X of the optical transmission unit is output from port Y after passing through the optical transmission unit, and the optical signal input from port Y of the optical transmission unit is output from port Z after passing through the optical transmission unit; When the optical transmission unit serves as the optical output end of the high-speed time phase encoding device, the optical signal input from port Z of the optical transmission unit is output from port Y after passing through the optical transmission unit, and the optical signal input from port Y of the optical transmission unit is output from port X after passing through the optical transmission unit.

3. The device according to claim 2, characterized in that When the optical transmission unit port X is the optical output port of the high-speed time phase encoding device, and the first optical coupler port A is the optical input port of the high-speed time phase encoding device, The first optical coupler splits an optical pulse input through port A into two optical pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is input into the second optical coupler through the first transmission optical route via the second optical coupler port D, and is output from the second optical coupler port G and port F; the second optical pulse is input into the second optical coupler through the second transmission optical route via the second optical coupler port E, and is output from the second optical coupler port G and port F; the first reflected sub-optical pulse output from the first optical pulse through the second optical coupler port G and the second reflected sub-optical pulse output from the second optical coupler port G and the second optical pulse are output from the second optical coupler port F. The second-path transmitted sub-optical pulse outputted from the coupler port G constitutes a third-path optical pulse, which is transmitted counterclockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port F; the first-path transmitted sub-optical pulse outputted from the first-path optical pulse through the second optical coupler port F and the second-path reflected sub-optical pulse outputted from the second optical coupler port F constitute a fourth-path optical pulse, which is transmitted clockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port G; the third-path optical pulse and the fourth-path optical pulse both contain optical pulses of two consecutive time slots within one pulse cycle; The first phase modulator performs phase modulation on the third path optical pulse input from the forward input optical port, or performs phase modulation on one of the two time slots of the third path optical pulse; The second optical coupler combines the third optical pulse and the fourth optical pulse after passing through the first phase modulator, and outputs them from the second optical coupler port D to the optical transmission unit port Y, and then outputs them through the optical transmission unit port X.

4. The device according to claim 2, characterized in that When the optical transmission unit port X is the optical input port of the high-speed time phase encoding device and the first optical coupler port A is the optical output port of the high-speed time phase encoding device, An optical pulse is input through the optical transmission unit port X, output from the optical transmission unit port Y to the second optical coupler port D, and split by the second optical coupler into two optical pulses, namely a first optical pulse and a second optical pulse; the first optical pulse is output from the second optical coupler port G, transmitted counterclockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port F; the second optical pulse is output from the second optical coupler port F, transmitted clockwise along the third transmission optical path through the first phase modulator and then to the second optical coupler port G; The first phase modulator performs phase modulation on the first path of optical pulses input from the forward input optical port; The second optical coupler combines the first optical pulse and the second optical pulse after passing through the first phase modulator, and outputs the combined optical pulse through port D and port E of the second optical coupler. The optical pulse output from port D is output to port Y of the optical transmission unit, and is output to port B of the first optical coupler through port Z of the optical transmission unit; the optical pulse output from port E is output to port C of the first optical coupler. Two optical pulses input into the first optical coupler from port B and port C of the first optical coupler are combined and output from port A of the first optical coupler.

5. The device according to claim 3, characterized in that The first phase modulator modulates one of the two time slots of the third path optical pulse by 0° or 180°.

6. The device according to any one of claims 1 to 5, characterized in that The two paths of light pulses pass through the first phase modulator simultaneously.

7. The device according to any one of claims 1 to 5, characterized in that The first phase modulator randomly modulates one of the two optical sub-pulses input from the forward input optical port by 0°, 90°, 180° or 270°.

8. The device according to claim 3, characterized in that The device further comprises: a second phase modulator and a second driver, The second phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator; The second phase modulator includes three ports, namely port L', port M' and electrical port N', port L' and port M' are respectively the forward input optical port and reverse input optical port of the second phase modulator; port L' and port M' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path, or port M' and port L' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path; the electrical port N' of the second phase modulator is connected to the second driver; the modulation signal applied by the second driver is received through the electrical port N', and the second phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

9. The device according to claim 8, characterized in that The device further includes: a third phase modulator and a third driver, The third phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator and the second phase modulator; The third phase modulator includes three ports, namely port L", port M", and port N", port L" and port M" are the forward input optical port and reverse input optical port of the third phase modulator, respectively. The electrical port N" of the third phase modulator is connected to the third driver and receives the modulation signal applied by the third driver through the electrical port N", and the third phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

10. The device according to claim 4, characterized in that The device further comprises: a second phase modulator and a second driver, The second phase modulator is arranged on the third transmission optical path and is connected in series with the first phase modulator; The second phase modulator includes three ports, namely port L', port M' and electrical port N', port L' and port M' are respectively the forward input optical port and reverse input optical port of the second phase modulator; port L' and port M' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path, or port M' and port L' are respectively connected to the second optical coupler port F and the first phase modulator port M through the third transmission optical path; the electrical port N' of the second phase modulator is connected to the second driver; the modulation signal applied by the second driver is received through the electrical port N', and the second phase modulator is in a non-reciprocal state after being applied with a high-frequency modulation signal with a frequency higher than a specified threshold, and the ratio of the modulation efficiency of the optical pulse input from the forward input optical port to the modulation efficiency of the optical pulse input from the reverse input optical port is greater than a preset threshold.

11. The device according to any one of claims 1 to 5, characterized in that The optical transmission unit is an optical coupler or an optical circulator.

12. The device according to any one of claims 1 to 5, characterized in that The device further comprises: an attenuator, The attenuator is arranged in the first transmission optical path or the second transmission optical path, and is used to adjust the loss of the two arms of the unequal-arm interferometer.

13. The device according to claim 1, characterized in that The first transmission optical path, the second transmission optical path and / or the third transmission optical path are polarization-maintaining optical fibers.

14. The device according to claim 13, characterized in that The second optical coupler port G and port F are both coupled to the slow axis of the polarization-maintaining optical fiber of the third transmission optical path, or are both coupled to the fast axis of the polarization-maintaining optical fiber of the third transmission optical path.

15. The device according to claim 1, characterized in that The first optical coupler and / or the second optical coupler is a polarization-maintaining fiber coupler.

16. A high-speed time phase encoding method, characterized in that: The high-speed time phase encoding device according to any one of claims 1 to 15 is used to implement high-speed time phase encoding.

17. A quantum communication system, characterized in that: The high-speed time phase encoding device comprises the device described in any one of claims 1 to 15.

Images