Quantum state decoding device and quantum communication system

Abstract

The utility model provides a quantum state decoding device and a quantum communication system. The quantum state decoding device comprises a first optical switch, a polarization decoding unit, a time phase decoding unit and a second optical switch, the input port of the first optical switch is used for receiving one path of input optical pulse; one output port of the first optical switch is connected with the input port of the polarization decoding unit, and the output port of the polarization decoding unit is connected with the input port of the second optical switch; the other output port of the first optical switch is connected with the input port of the time phase decoding unit, and the output port of the time phase decoding unit is connected with the input port of the second optical switch. By the adoption of the scheme, the quantum state decoding device can be compatible with the polarization decoding mode and the time phase decoding mode, and the structure is simple.

Description

Technical Field

[0001] This application relates to the technical fields of quantum communication and optical quantum decoding, and in particular to a quantum state decoding device and a quantum communication system. Background Art

[0002] Quantum communication technology is a frontier and hot field that combines quantum physics and information science. Currently, its applications mainly include quantum key distribution and quantum direct communication. Based on physical principles such as the Heisenberg uncertainty relation and the quantum no-cloning theorem in quantum mechanics, quantum key distribution can securely share keys in real time between two communication parties, and quantum direct communication can achieve secure information transmission. Quantum communication can detect potential eavesdropping behaviors in communication channels and can be applied to fields with high-security information transmission requirements such as national defense, government affairs, finance, and power.

[0003] The physical implementation of a quantum communication system, such as the physical implementation of quantum key distribution and quantum direct communication, requires encoding and decoding of quantum states. Currently, practical quantum communication systems mainly use polarization encoding or time-phase encoding, and the corresponding decoding methods are polarization decoding and time-phase decoding. Existing quantum communication generally uses a decoding device with a single decoding method to decode a coded signal. Summary of the Utility Model

[0004] This application provides a quantum state decoding device and a quantum communication system to solve the above technical problems in the prior art.

[0005] According to the first aspect of this application, a quantum state decoding device is provided, including: a first optical switch, a polarization decoding unit, a time-phase decoding unit, and a second optical switch;

[0006] The first optical switch includes an input port and two output ports, namely a first port, a second port, and a third port. The first port is the input port of the quantum state decoding device and is used to receive an input optical pulse;

[0007] The polarization decoding unit includes an input port and at least one output port;

[0008] The time-phase decoding unit includes an input port and at least one output port;

[0009] The second optical switch includes at least two input ports and at least one output port, and the output port is the output port of the quantum state decoding device;

[0010] The second port of the first optical switch is connected to the input port of the polarization decoding unit, and the output port of the polarization decoding unit is connected to the input port of the second optical switch;

[0011] The third port of the first optical switch is connected to the input port of the time-phase decoding unit, and the output port of the time-phase decoding unit is connected to the input port of the second optical switch.

[0012] In some embodiments, the polarization decoding unit includes: a first optical splitter, a first polarization beam splitter, and a second polarization beam splitter;

[0013] The first optical splitter includes an input port and two output ports, and the input port of the first optical splitter is connected to the second port of the first optical switch;

[0014] The first polarization beam splitter includes an input port and two output ports, and the input port of the first polarization beam splitter is connected to one of the two output ports of the first optical splitter;

[0015] The second polarization beam splitter includes an input port and two output ports, and the input port of the second polarization beam splitter is connected to the other of the two output ports of the first optical splitter;

[0016] The output ports of the first polarization beam splitter and the output ports of the second polarization beam splitter are both connected to the input port of the second optical switch.

[0017] In some embodiments, the polarization decoding unit further includes: a second optical splitter and a third polarization beam splitter;

[0018] The second optical splitter includes an input port and two output ports. The input port of the second optical splitter is the input port of the polarization decoding unit, which is connected to the second port of the first optical switch. One of the two output ports of the second optical splitter is connected to the input port of the first optical splitter;

[0019] The third polarization beam splitter includes an input port and two output ports. The other of the two output ports of the second optical splitter is connected to the input port of the third polarization beam splitter, and the two output ports of the third polarization beam splitter are both connected to the input port of the second optical switch.

[0020] In some embodiments, the second optical splitter is a 1:2 optical splitter.

[0021] In some embodiments, the polarization decoding unit further includes: a quarter-wave plate and a half-wave plate;

[0022] The quarter-wave plate is disposed at the front end of any one of the polarization beam splitters;

[0023] The half-wave plate is disposed at the front end of the any one of the polarization beam splitters and is not disposed in front of the same polarization beam splitter as the quarter-wave plate.

[0024] In some embodiments, the polarization decoding unit further includes: a quarter-wave plate or a half-wave plate;

[0025] The quarter-wave plate or the half-wave plate is disposed at the front end of any one of the polarization beam splitters.

[0026] In some embodiments, the time-phase decoding unit is an unequal-arm Mach-Zehnder interferometer or an unequal-arm Michelson interferometer.

[0027] In some embodiments, the time-phase decoding unit further includes: a third optical beam splitter;

[0028] The third optical beam splitter includes an input port and two output ports. The input port of the third optical beam splitter is the input port of the time-phase decoding unit, and one of the two output ports of the third optical beam splitter is connected to the input port of the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer;

[0029] The other of the two output ports of the third optical beam splitter and the output port of the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer are both connected to the input port of the second optical switch.

[0030] In some embodiments, the time-phase decoding unit further includes: a fourth optical beam splitter;

[0031] The fourth optical beam splitter includes an input port and two output ports. The input port of the fourth optical beam splitter is connected to the other of the two output ports of the third optical beam splitter;

[0032] The two output ports of the fourth optical beam splitter are connected to the input port of the second optical switch.

[0033] In some embodiments, the two mirrors of the unequal-arm Michelson interferometer are 90° Faraday rotation mirrors or quarter-wave plate mirrors.

[0034] In some embodiments, the second optical switch is an 8×4 matrix optical switch.

[0035] According to a second aspect of the present application, there is provided a quantum communication system including the above-mentioned quantum state decoding device.

[0036] In summary, the quantum state decoding device and the quantum communication system provided by the present application have at least the following beneficial effects:

[0037] The quantum state decoding device provided by this application forms a first optical decoding branch through the transmission paths of a first optical switch, a polarization decoding unit, and a second optical switch, and forms a second optical decoding branch through the transmission paths of the first optical switch, a time-phase decoding unit, and a second optical switch. When an optical pulse is input to the first optical switch, it can output a polarization-decoded quantum state optical pulse through the first optical decoding branch where the polarization decoding unit is located, or output a time-phase decoded quantum state optical pulse through the second optical decoding branch where the time-phase decoding unit is located. Thus, a decoding device can be used for both polarization decoding and time-phase decoding, compatible with two decoding methods, and has a simple structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the specific embodiments of this application, the following will briefly introduce the drawings required for use in the specific embodiments in conjunction with the drawings. Obviously, the drawings in the following description are some embodiments of this application. For those skilled in the art, without creative efforts, other drawings or solutions can also be obtained based on these drawings.

[0039] Figure 1 It is a structural diagram of the quantum state decoding device in an embodiment of this application;

[0040] Figure 2 It is a structural diagram of the polarization decoding unit in an embodiment of this application;

[0041] Figure 3 It is a structural diagram of the polarization decoding unit in another embodiment of this application;

[0042] Figure 4 It is a structural diagram of the time-phase decoding unit in an embodiment of this application;

[0043] Figure 5 It is a structural diagram of the time-phase decoding unit in another embodiment of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] In order to make the above and other features and advantages of this application clearer, the following further describes this application in conjunction with the 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 merely exemplary and not restrictive.

[0045] In the following description, many specific details are set forth to provide a thorough understanding of this application. However, it is obvious to those skilled in the art that specific details do not need to be employed to practice this application. In other cases, well-known steps or operations are not described in detail to avoid obscuring this application.

[0046] 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, Y-phase basis, and Z-time basis; the time-phase decoding includes phase decoding, that is, the time-phase decoding is to decode the encoded quantum state composed of any combination of quantum states of the X-phase basis, Y-phase basis, and Z-time basis.

[0047] Reference Figure 1 , this application provides a quantum state decoding device, including: a first optical switch 101, a polarization decoding unit 102, a time-phase decoding unit 103, and a second optical switch 104.

[0048] Among them, the first optical switch 101 includes an input port and two output ports, namely the first port, the second port, and the third port. The first port is the input port of the quantum state decoding device and is used to receive an input optical pulse; the second port and the third port are output ports respectively. When an optical pulse is input at the first port of the first optical switch 101, it is output from the second port or the third port.

[0049] Among them, the polarization decoding unit 102 includes an input port and at least one output port. The input port of the polarization decoding unit 102 is the fourth port. The polarization encoding unit 102 is used to perform polarization decoding on the input optical pulse and output a polarization-decoded quantum state optical pulse.

[0050] Among them, the time-phase decoding unit 103 includes an input port and at least one output port. The input port of the time-phase decoding unit 103 is the fifth port. The time-phase decoding unit 103 is used to perform time-phase decoding on the input optical pulse and output a time-phase decoded quantum state optical pulse.

[0051] Among them, the second optical switch 104 includes at least two input ports and at least one output port. The output port of the second optical switch 104 is the output port of the quantum state decoding device.

[0052] Specifically, the second port of the first optical switch 101 is connected to the input port of the polarization decoding unit 102, and the output port of the polarization decoding unit 102 is connected to the input port of the second optical switch 104 to form a first optical decoding branch.

[0053] The third port of the first optical switch 101 is connected to the input port of the time-phase decoding unit 103, and the output port of the time-phase decoding unit 103 is connected to the input port of the second optical switch 104 to form a second optical decoding branch.

[0054] The above-mentioned quantum state decoding device forms a first optical decoding branch through the transmission paths of the first optical switch 101, the polarization decoding unit 102, and the second optical switch 104, and forms a second optical decoding branch through the transmission paths of the first optical switch 101, the time-phase decoding unit 103, and the second optical switch 104. When an optical pulse is input to the first optical switch 101, a polarization-decoded quantum state optical pulse can be output through the first optical decoding branch where the polarization decoding unit 102 is located, or a time-phase decoded quantum state optical pulse can be output through the second optical decoding branch where the time-phase decoding unit 103 is located. Thus, a decoding device can be used for both polarization decoding and time-phase decoding, compatible with two decoding methods. By outputting the decoded quantum state optical pulse through the second optical switch 104, the number of single-photon detectors used can be reduced. The quantum state decoding device provided by this application has low cost and simple structure.

[0055] As Figure 2 shown, in one of the embodiments, the polarization decoding unit 102 includes: a first optical beam splitter 201, a first polarization beam splitter 202, and a second polarization beam splitter 203.

[0056] Among them, the first optical beam splitter 201 includes an input port and two output ports. The input port of the first optical beam splitter is connected to the second port of the first optical switch 101. The first polarization beam splitter 202 includes an input port and two output ports. The input port of the first polarization beam splitter 202 is connected to one of the two output ports of the first optical beam splitter 201. The second polarization beam splitter 203 includes an input port and two output ports. The input port of the second polarization beam splitter 203 is connected to the other of the two output ports of the first optical beam splitter 201. The output ports of the first polarization beam splitter 202 and the second polarization beam splitter 203 are both connected to the input port of the second optical switch 104.

[0057] Specifically, the optical pulse output by the first optical switch 101 is split after passing through the first optical beam splitter 201. One path is transmitted to the first polarization beam splitter 202 for polarization splitting, and the other path is transmitted to the second polarization beam splitter 203 for polarization splitting. By adopting the structure of connecting the first optical beam splitter 201 to the first polarization beam splitter 202 and the second polarization beam splitter 203 respectively for polarization decoding, the structure is simple and easy to implement.

[0058] As Figure 3 shown, in one of the embodiments, the polarization decoding unit 102 further includes: a second optical beam splitter 204 and a third polarization beam splitter 205.

[0059] Among them, the second optical beam splitter 204 includes an input port and two output ports. The input port of the second optical beam splitter 204 is the input port of the polarization decoding unit 102 and is connected to the second port of the first optical switch 101; one of the two output ports of the second optical beam splitter 204 is connected to the input port of the first optical beam splitter 201.

[0060] Among them, the third polarization beam splitter 205 includes an input port and two output ports. The other of the two output ports of the second optical beam splitter 204 is connected to the input port of the third polarization beam splitter 205, and both output ports of the third polarization beam splitter 205 are connected to the input port of the second optical switch 104.

[0061] Specifically, the optical pulse output by the first optical switch 101 is split after passing through the second optical beam splitter 204. One path is transmitted to the third polarization beam splitter 205 for polarization splitting, and the other path is transmitted to the first optical beam splitter 201 for splitting and then respectively transmitted to the first polarization beam splitter 202 and the second polarization beam splitter 203 for polarization splitting. In this way, polarization decoding can be accurately and effectively performed.

[0062] Further, the second optical beam splitter 204 is a 1:2 optical beam splitter, such that the light intensity ratios of the light input to the first polarization beam splitter 202, the second polarization beam splitter 203, and the third polarization beam splitter 205 are 1:1:1.

[0063] In one embodiment, the polarization decoding unit 102 further includes: a quarter-wave plate and a half-wave plate. The quarter-wave plate is disposed at the front end of any one of the polarization beam splitters, and the half-wave plate is disposed at the front end of any one of the polarization beam splitters and is not disposed in front of the same polarization beam splitter as the quarter-wave plate. For example, Figure 2 In the illustrated embodiment, a quarter-wave plate may be disposed at the front end of one of the first polarization beam splitter 202 and the second polarization beam splitter 203, and a half-wave plate may be disposed at the front end of the other. Figure 3 In the illustrated embodiment, a quarter-wave plate is disposed at the front end of any one of the first polarization beam splitter 202, the second polarization beam splitter 203, and the third polarization beam splitter 205, and a half-wave plate is disposed at the front end of one of the other two polarization beam splitters.

[0064] In other embodiments, the polarization decoding unit 102 further includes a quarter-wave plate or a half-wave plate. The quarter-wave plate or the half-wave plate is disposed at the front end of any one of the polarization beam splitters. That is, one type of wave plate is disposed at the front end of any one of the polarization beam splitters of the polarization decoding unit 102. For example, Figure 2 In the illustrated embodiment, a quarter-wave plate or a half-wave plate may be disposed at the front end of the first polarization beam splitter 202 or the second polarization beam splitter 203. Figure 3In the illustrated embodiment, a quarter-wave plate or a half-wave plate may be disposed at the front end of the first polarization beam splitter 202, the second polarization beam splitter 203, or the third polarization beam splitter 205.

[0065] In one embodiment, the time phase decoding unit 103 is an unequal-arm Mach-Zehnder interferometer or an unequal-arm Michelson interferometer.

[0066] In one implementation, referring Figure 4 and Figure 5 , the time phase decoding unit 103 further includes a third optical beam splitter 301; the third optical beam splitter 301 includes an input port and two output ports. The input port of the third optical beam splitter 301 is the input port of the time phase decoding unit 103 and is connected to the third port of the first optical switch 101. One of the two output ports of the third optical beam splitter 301 is connected to the input port of the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer. For example Figure 4 the input port of the unequal-arm Mach-Zehnder interferometer in Figure 5 is connected to one output port of the third optical beam splitter 301, Figure 4 and the input port of the unequal-arm Michelson interferometer in Figure 5 is connected to one output port of the third optical beam splitter 301. The other output port of the two output ports of the third optical beam splitter 301 and the output ports of the unequal-arm Mach-Zehnder interferometer ( Figure 4 shown) or the unequal-arm Michelson interferometer ( Figure 5 shown) are all connected to the input port of the second optical switch 104.

[0067] By using the third optical beam splitter to split the optical pulse output by the first optical switch 101, one path is transmitted to the second optical switch 104, and one path is transmitted to the second optical switch 104 after passing through the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer, so as to realize the time phase decoding of the optical pulse.

[0068] Further, as Figure 4 and Figure 5 described, the time phase decoding unit 103 further includes a fourth optical beam splitter 302. The fourth optical beam splitter 302 includes an input port and two output ports. The input port of the fourth optical beam splitter 302 is connected to the other of the two output ports of the third optical beam splitter 301; the two output ports of the fourth optical beam splitter 302 are connected to the input port of the second optical switch 102. By adding the fourth optical beam splitter 302 on the basis of the third optical beam splitter 301, multi-path split output is realized.

[0069] Specifically, as Figure 4As shown in the figure, the unbalanced Mach-Zehnder interferometer includes two optical coupling units, namely the first optical coupling unit 303 and the second optical coupling unit 304. The input port of the first optical coupling unit 303 is connected to an output port of the third optical beam splitter 301. One output port of the first optical coupling unit 303 is connected to one input port of the second optical coupling unit 304, and the other output port of the first optical coupling unit 303 is connected to the other input port of the second optical coupling unit 304. The two output ports of the second optical coupling unit 304 are connected to the input port of the second optical switch 104.

[0070] Specifically, as Figure 5 shown in the figure, the unbalanced Michelson interferometer includes a third optical coupling unit 305 and two mirrors. The input port of the third optical coupling unit 305 is connected to an output port of the third optical beam splitter 301. A mirror is respectively arranged in front of each of the two output ports of the third optical coupling unit 305.

[0071] In one embodiment, the two mirrors of the unbalanced Michelson interferometer are 90° Faraday rotation mirrors or quarter-wave plate mirrors to achieve effective light reflection.

[0072] In one embodiment, the second optical switch 104 is an 8×4 matrix optical switch to achieve multi-channel input and multi-channel output. For example, the polarization decoding unit 102 is as Figure 2 shown in the figure, the time-phase decoding unit 103 is as Figure 4 or Figure 5 shown in the figure. Then, the polarization decoding unit 102 outputs 4 optical pulses to the second optical switch 104, and the time-phase decoding unit 103 outputs 4 optical pulses to the second optical switch 104. Therefore, 8 input ports are required for the second optical switch 104. Using an 8×4 matrix optical switch can meet the input requirements of the second optical switch 104.

[0073] In the embodiment of the present application, the optical switch 104 outputs optical pulses of decoded quantum states, which can reduce the number of single-photon detectors used. Specifically, for example, if the polarization decoding unit 102 outputs 4 polarization-decoded quantum states, 4 single-photon detectors are required to be connected to the output ports. If the time-phase decoding unit 103 outputs 4 time-phase decoded quantum states, 4 single-photon detectors are required to be connected to the output ports subsequently. By using the optical switch 104 (8×4 matrix optical switch) of the embodiment of the present application, the 4 outputs of the polarization decoding are connected to 4 of the 8 input ports of the optical switch 104, and the 4 outputs of the time-phase decoding are connected to the other 4 of the 8 input ports of the optical switch 104. Through the selective connection of the optical switch 104, 4 polarization-decoded quantum states or 4 time-phase decoded quantum states can be output. Only 4 single-photon detectors need to be connected to the 4 output ports of the optical switch 104, which can save the use of single-photon detectors. Therefore, the design of the present application effectively saves costs.

[0074] The present application provides a quantum communication system, including the quantum state decoding device in each of the above embodiments.

[0075] Similarly, the above quantum communication system can be compatible with two quantum state decoding methods and has a simple structure.

[0076] The above-described technical features 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 a combination does not conflict.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application and are not intended to limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and 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 quantum state decoding device, characterized in that, Including: A first optical switch, a polarization decoding unit, a time-phase decoding unit, and a second optical switch; The first optical switch includes an input port and two output ports, namely a first port, a second port, and a third port. The first port is the input port of the quantum state decoding device and is used to receive an input optical pulse; The polarization decoding unit includes an input port and at least one output port; The time-phase decoding unit includes an input port and at least one output port; The second optical switch includes at least two input ports and at least one output port. The output port is the output port of the quantum state decoding device; The second port of the first optical switch is connected to the input port of the polarization decoding unit, and the output port of the polarization decoding unit is connected to the input port of the second optical switch; The third port of the first optical switch is connected to the input port of the time-phase decoding unit, and the output port of the time-phase decoding unit is connected to the input port of the second optical switch.

2. The quantum state decoding device according to claim 1, characterized in that The polarization decoding unit includes: a first optical beam splitter, a first polarization beam splitter, and a second polarization beam splitter; The first optical beam splitter includes an input port and two output ports. The input port of the first optical beam splitter is connected to the second port of the first optical switch; The first polarization beam splitter includes an input port and two output ports. The input port of the first polarization beam splitter is connected to one of the two output ports of the first optical beam splitter; The second polarization beam splitter includes an input port and two output ports. The input port of the second polarization beam splitter is connected to the other of the two output ports of the first optical beam splitter; The output ports of the first polarization beam splitter and the second polarization beam splitter are both connected to the input port of the second optical switch.

3. The quantum state decoding device according to claim 2, wherein The polarization decoding unit further includes: a second optical beam splitter and a third polarization beam splitter; The second optical beam splitter includes an input port and two output ports. The input port of the second optical beam splitter is the input port of the polarization decoding unit and is connected to the second port of the first optical switch. One of the two output ports of the second optical beam splitter is connected to the input port of the first optical beam splitter; The third polarization beam splitter includes an input port and two output ports. The other of the two output ports of the second optical beam splitter is connected to the input port of the third polarization beam splitter. The two output ports of the third polarization beam splitter are both connected to the input port of the second optical switch.

4. The quantum state decoding device according to claim 3, wherein The second optical beam splitter is a 1:2 optical beam splitter.

5. The quantum state decoding device according to any one of claims 2-4, characterized in that, The polarization decoding unit further includes: a quarter-wave plate and a half-wave plate; The quarter-wave plate is disposed in front of any one of the polarization beam splitters; The half-wave plate is disposed in front of the any one of the polarization beam splitters and is not disposed in front of the same polarization beam splitter as the quarter-wave plate.

6. The quantum state decoding device according to any one of claims 2-4, characterized in that The polarization decoding unit further includes: a quarter-wave plate or a half-wave plate; The quarter-wave plate or the half-wave plate is disposed in front of any one of the polarization beam splitters.

7. The quantum state decoding device according to claim 1, characterized in that, The time-phase decoding unit is an unequal-arm Mach-Zehnder interferometer or an unequal-arm Michelson interferometer.

8. The quantum state decoding device according to claim 7, wherein The time-phase decoding unit further includes: a third optical beam splitter; The third optical beam splitter includes an input port and two output ports. The input port of the third optical beam splitter is the input port of the time-phase decoding unit, and one of the two output ports of the third optical beam splitter is connected to the input port of the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer; The other of the two output ports of the third optical beam splitter and the output port of the unequal-arm Mach-Zehnder interferometer or the unequal-arm Michelson interferometer are both connected to the input port of the second optical switch.

9. The device according to claim 8, characterized in that, The time-phase decoding unit further includes: a fourth optical beam splitter; The fourth optical beam splitter includes an input port and two output ports. The input port of the fourth optical beam splitter is connected to the other of the two output ports of the third optical beam splitter; The two output ports of the fourth optical beam splitter are connected to the input port of the second optical switch.

10. The device according to claim 7, characterized in that, The two mirrors of the unequal-arm Michelson interferometer are 90° Faraday rotation mirrors or quarter-wave plate mirrors.

11. The device according to claim 2 or 9, characterized in that, The second optical switch is an 8×4 matrix optical switch.

12. A quantum communication system, characterized in that, It includes the quantum state decoding device according to any one of claims 1 to 11.

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