Dynamic user phase coding quantum communication system

Abstract

The utility model discloses a dynamic user phase coding quantum communication system, and the system is characterized in that a laser LD generates a pulse optical signal which enters a first SC device for initial phase modulation, and then enters a polarization modulation module for phase loading and polarization state adjustment; a pulse light signal is modulated into a signal state or decoy state pulse through an intensity modulator IM, the signal state or decoy state pulse is attenuated into a single photon level through an attenuator ATT, then the single photon level enters a selected user side Bob in each period, and the single photon level enters an original path after being modulated at the user side Bob; and after returning, interference is generated at the 50: 50 beam splitter BS, and finally the light is emitted to the detection unit for detection. According to the utility model, the phase encoder and the plurality of polarization encoders are arranged, so that the strong anti-interference capability is improved; a plurality of polarization encoders are utilized to adjust the pulse optical signal into a polarization state to select a user, so that different users can perform independent communication on the same quantum channel, and the flexibility of quantum network user selection is greatly improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to quantum communication and quantum computing field, concretely relates to a dynamic user phase encoding quantum communication system. BACKGROUND

[0002] Quantum communication technology utilizes the principles of quantum mechanics, especially quantum superposition and entanglement, to achieve secure transmission of information. Compared with traditional communication technology, quantum communication has extremely high security and cannot be eavesdropped or tampered with. Therefore, it has wide application prospects in the fields of military, financial and government confidential communication. The core technologies of quantum communication include quantum key distribution (QKD), quantum teleportation and quantum network, etc.

[0003] At present, quantum communication mainly relies on two encoding methods: polarization encoding and phase encoding. Polarization encoding uses the polarization state of photons to transmit information, while phase encoding controls the phase of photons to achieve information transmission. These methods, although to some extent, ensure the secure transmission of information, but each has some limitations.

[0004] Quantum key distribution systems can use polarization, phase and other optical degrees of freedom encoding. Polarization encoding: this method is simple and easy to implement, but in long distance transmission, it is easily affected by environmental noise and polarization mode dispersion, leading to signal attenuation and increased bit error rate. Phase encoding: phase encoding technology has high anti-interference ability to environmental noise, but in the multi-user communication scenario, how to effectively select and distinguish the information of different users is still a challenge.

[0005] Therefore, it is necessary to further improve the existing polarization and phase encoding to improve the anti-interference ability and user selection flexibility of the existing quantum communication, and to achieve more efficient and secure quantum communication. UTILITY MODEL CONTENT

[0006] In order to solve the above technical problems, the utility model provides a polarization selection user's quantum communication system based on phase encoding with strong anti-interference ability and user selection flexibility.

[0007] In order to achieve the above object, the technical scheme adopted by the utility model is as follows: a dynamic user phase encoding quantum communication system, comprising an LD laser LD, a first CIR circulator, a first SC device, a first polarization controller PC1, a polarization modulation module, a second CIR circulator, an intensity modulator IM, an attenuator ATT, a third CIR circulator, a detection unit, a 50:50 beam splitter BS, a second polarization controller PC2, a second four-port polarization beam splitter PBS2, a second delay line DL, a second SC device, a first receiving end Bob1, a third polarization controller PC3, a third four-port polarization beam splitter PBS3, a third delay line DL, a third SC device, wherein:

[0008] The laser LD is used for generating a pulsed optical signal;

[0009] The first CIR circulator transmits the pulsed optical signal to the first SC device and the first polarization controller PC1;

[0010] The first SC device is used for modulating the initial phase φ of the initial pulsed optical signal A ∈{0, π / 2, π, 3π / 2};

[0011] The first polarization controller PC1 is used for modulating the initial pulsed optical signal into a 45° polarization state;

[0012] The polarization modulation module is used for phase loading and polarization state adjustment of the 45° polarization state pulsed optical signal into a horizontal polarization state;

[0013] The intensity modulator IM is used for modulating the pulsed optical signal into a signal state or a decoy state pulse;

[0014] The attenuator ATT attenuates the pulsed optical signal to a single photon level;

[0015] The 50:50 beam splitter BS is used for splitting the pulsed optical signal into first and second beam two-part pulsed optical signals;

[0016] The first beam passes through the second four-port polarization beam splitter PBS2 to reach the selected user end Bob1, and returns to the original route after modulation at the user end Bob1;

[0017] The second beam passes through the third four-port polarization beam splitter PBS3 to reach the selected user end Bob2, and returns to the original route after modulation at the user end Bob2;

[0018] When the returned first and second beams reach the 50:50 beam splitter BS at the same time, they are emitted to the detection unit for detection after passing through the third CIR circulator.

[0019] Preferably, the polarization modulation module comprises a first polarization beam splitter PBS1, a first phase modulator PM1, a first Faraday rotator FR1 and a first delay line DL;

[0020] The input port of the first polarization beam splitter PBS1 is connected with a first CIR circulator through an optical signal; one output port of the first polarization beam splitter PBS1 is connected with a first Faraday rotator FR1 through a first delay line DL;

[0021] The other output port of the first polarization beam splitter PBS1 is connected with the first phase modulator PM1 through an optical signal.

[0022] The first phase modulator PM1 is connected with the first Faraday rotator FR1 through an optical signal.

[0023] Preferably, the detection unit comprises a first single-photon detector D1 and a second single-photon detector D2.

[0024] Preferably, the first polarization controller PC1 adjusts the initial pulse optical signal to be a 45° polarized pulse optical signal, and after the 45° polarized pulse optical signal is sent to the first polarization beam splitter PBS1, the 45° polarized pulse optical signal is divided into horizontal polarization H and vertical polarization at the same probability;

[0025] The horizontal polarization pulse transmits through the first polarization beam splitter PBS1.

[0026] The vertical polarization pulse first passes through the first phase modulator PM1 to load a phase △φ, and then becomes a horizontal polarization state after passing through the first Faraday rotator FR1 and the first delay line DL, and then transmits through the first polarization beam splitter PBS1 to return to the first CIR circulator R.

[0027] The vertical polarization state |V> of the vertical polarization pulse V introduces an additional phase of π / 2 after being reflected by the first polarization beam splitter PBS1.

[0028] The horizontal polarization state |H> of the horizontal polarization pulse transmits through the first Faraday rotator FR1 and is reflected back to the first CIR circulator at the first polarization beam splitter PBS1.

[0029] Preferably, the pulse of the vertical polarization state |V> first passes through the first phase modulator PM1 to load a phase △φ, and then the vertical polarization state |V> is combined with the horizontal polarization state |H> at the first polarization beam splitter PBS1, and the combined pulse after the combination is transmitted to the intensity modulator IM.

[0030] Preferably, the intensity modulator IM modulates the combined pulse optical signal into signal state or decoy state pulses, and then transmits to the attenuator ATT, the attenuator ATT attenuates the signal state or decoy state pulses to single photon level to obtain single photon pulses.

[0031] Preferably, the single photon pulses pass through the third CIR circulator to the 50:50 beam splitter BS113, and the single photon pulses are divided into first and second optical paths at the 50:50 beam splitter BS113, and the single photon pulses in the first and second optical paths pass through the second four-port polarization beam splitter PBS2 and the third four-port polarization beam splitter PBS3 respectively to reach the corresponding selected user terminals Bob1 and Bob2.

[0032] Preferably, the horizontal polarization state |H> and the vertical polarization state |V> are represented by a Jones matrix:

[0033]

[0034] Preferably, the vertical polarization state |V> introduces an additional phase of π / 2 after being reflected by the first polarization beam splitter PBS1, and the Jones matrix representation of the first Faraday rotator FR1 is:

[0035]

[0036] Preferably, the horizontal polarization state |H> after passing through the first Faraday rotator FR1 is represented as:

[0037]

[0038] The beneficial technical effects of the utility model: the utility model is provided with a phase encoder and a plurality of polarization encoders arranged step by step to modulate pulse optical signal signals, the phase encoder has high anti-interference ability to environmental noise and interference, guarantees the stability and reliability of signals, and realizes strong anti-interference ability.

[0039] The plurality of polarization encoders are used to adjust pulse optical signal signals into polarization state selected users, so that different users can independently communicate on the same quantum channel, greatly improving the flexibility of user selection and improving flexibility and expansibility. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 It is the overall structure block diagram of the utility model one kind dynamic user phase encoding quantum communication system;

[0041] Figure 2 It is the structure schematic view of the utility model one kind dynamic user phase encoding quantum communication system SC device. DETAILED DESCRIPTION

[0042] To make the objectives, technical solutions and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the embodiments. However, the scope of protection of this utility model is not limited to the specific embodiments described below.

[0043] like Figure 1 As shown, a dynamic user phase-coded quantum communication system includes an LD laser 101, a first CIR circulator 102, a first SC (Sagnac ring) device 103, a first polarization controller PC 1104, a polarization modulation module, a second CIR circulator 105, an intensity modulator IM 110, an attenuator ATT 111, a third CIR circulator 112, a detection unit, a 50:50 beam splitter BS 113, a second polarization controller PC 2114, a second four-port polarization beam splitter PBS 2, a second delay line DL 116, a second SC device 117, a first receiver Bob 1118, a third polarization controller PC 3119, a third four-port polarization beam splitter PBS 3120, a third delay line DL 121, and a third SC device 122, wherein:

[0044] The laser LD 101 is used to generate pulsed light signals;

[0045] The first CIR circulator 102 transmits the pulsed light signal to the first SC device 103 and the first polarization controller PC1104;

[0046] The first SC device 103 is used to modulate the initial phase φ of the initial pulse optical signal. A ∈{0,π / 2,π,3π / 2};

[0047] The first polarization controller PC1104 is used to modulate the initial pulsed light signal into a 45° polarization state;

[0048] The polarization modulation module is used to phase-load and polarization-adjust the 45° polarized pulsed light signal to change it to a horizontal polarization state.

[0049] Specifically, the polarization modulation module includes a first polarization beam splitter PBS1106, a first phase modulator PM1107, a first Faraday rotator FR1108, and a first delay line DL 109;

[0050] The input port of the first polarization beam splitter PBS1106 is connected to the first CIR circulator 102 via an optical signal; one output port of the first polarization beam splitter PBS1106 is connected to the first Faraday rotator FR1108 via the first delay line DL 109.

[0051] The other output port of the first polarization beam splitter PBS 1106 is connected to the first phase modulator PM 1107 through an optical signal.

[0052] The first phase modulator PM 1107 is connected to the first Faraday rotator FR 1108 through an optical signal.

[0053] The intensity modulator IM 110 is used to modulate the pulsed optical signal into signal state or decoy state pulses;

[0054] The attenuator ATT 111 attenuates the pulsed optical signal to a single photon level;

[0055] The 50:50 beam splitter BS 113 is used to divide the pulsed optical signal into two parts of the first beam and the second beam;

[0056] The first beam passes through the second four-port polarization beam splitter PBS2 115 to the selected user end Bob 1118, and returns to the original route after modulation at the user end Bob 1118;

[0057] The second beam passes through the third four-port polarization beam splitter PBS3 120 to the selected user end Bob 2123, and returns to the original route after modulation at the user end Bob 2123;

[0058] The returned first beam and second beam reach the 50:50 beam splitter BS 113 at the same time, and then pass through the CIR circulator 112 for the third time, and are emitted to the detection unit for detection.

[0059] The detection unit includes a first single photon detector D1 124 and a second single photon detector D2 125.

[0060] Specifically, the specific working process of the embodiment is as follows:

[0061] First, the laser LD 101 generates an initial pulsed optical signal into the first CIR circulator 102, and the first CIR circulator 102 transmits the pulsed optical signal to the first SC device 103 and the first polarization controller PC 1104; the first SC device 103 modulates the initial phase φ of the initial pulsed optical signal A ∈{0,π / 2,π,3π / 2}; the first polarization controller PC 1104 adjusts the initial pulsed optical signal into a 45° polarized pulsed optical signal, and after the 45° polarized pulsed optical signal is sent to the first polarization beam splitter PBS 1106, the 45° polarized pulsed optical signal is divided into two parts of horizontal polarization pulse H and vertical polarization pulse V with the same probability;

[0062] Wherein, the horizontal polarization pulse H transmits through the first polarization beam splitter PBS1 106; the vertical polarization pulse V first loads a phase of D after passing through the first phase modulator PM1 107, then becomes a horizontal polarization state after passing through the first Faraday rotator FR1 108 and the first delay line DL 109, and then transmits through the first polarization beam splitter PBS1 106 to the first CIR circulator 105. Therefore, the polarization direction of the combined pulse depends on the phase difference D between the two split pulses.

[0063] The specific transmission process of the horizontal polarization pulse H and the vertical polarization pulse V is as follows:

[0064] The vertical polarization state |V> of the vertical polarization pulse introduces an additional phase of π / 2 after being reflected by the first polarization beam splitter PBS1; the horizontal polarization state |H> of the horizontal polarization pulse passes through the first Faraday rotator FR1, and then the horizontal polarization state |H> passes through the first phase modulator PM1 107 without any modulation at the first phase modulator PM1 107, and is input to the first polarization beam splitter PBS1 106 to be reflected back to the first CIR circulator 105.

[0065] Similarly, the pulse of the vertical polarization state |V> first loads a phase of D at the first phase modulator PM1 107, and then the vertical polarization state |V> is combined with the horizontal polarization state |H> at the first polarization beam splitter PBS1 106. The combined pulse after combination is transmitted to the intensity modulator IM 110.

[0066] The intensity modulator IM 110 modulates the combined pulse optical signal into a signal state or a decoy state pulse, and then transmits it to the attenuator ATT 111. The attenuator ATT 111 attenuates the signal state or the decoy state pulse to a single photon level to obtain a single photon pulse.

[0067] Subsequently, the single photon pulse passes through the third CIR circulator 112 to the 50:50 beam splitter BS 113. The single photon pulse is split into two parts at the 50:50 beam splitter BS 113, into a first light path and a second light path. The single photon pulses in the first light path and the second light path pass through the second four-port polarization beam splitter PBS2 and the third four-port polarization beam splitter PBS3, respectively, to reach the corresponding selected user terminals Bob1 118 and Bob2 123.

[0068] When the single photon pulses are modulated by the user Bob 1 118 or Bob 2 123, they return to Alice. Since all the pulse light signals pass through a round trip path, the phase shift caused by birefringence in the fiber can be automatically compensated. When the two separated pulse light signals arrive at the 50:50 beam splitter BS 113 at the same time, they pass through the third CIR circulator 112 and enter the detection unit. The first single photon detector D 1124 and the second single photon detector D 2125 of the detection unit respond to the interference results. The specific detection method and principle are not described in detail here.

[0069] If Alice wants to share a string of secure keys with Bob 1, Alice should first modulate the pulse light signal by the polarization modulation module composed of the first polarization beam splitter PBS 1106, the first phase modulator FM 1107, the first Faraday rotator FR 1108, and the first delay line DL 109 to make the polarization state of the pulse light signal |D>. After passing through the second and third four-port polarization beam splitters PBS 2115 and PBS 3120, the pulse light signal becomes a superposition state of the paths, which can be expressed as:

[0070]

[0071] The single photon pulses of the first optical path first enter Bob 1, pass through Bob 1 without phase modulation and then return. Then, these pulses pass through the second and third four-port polarization beam splitters PBS 2115 and PBS 3120 by path one and return to Alice. Next, the pulse light signal loads the phase φ A (0 or π) when passing through the third SC device 122. Since the polarization state of the pulse has changed by 90°, the pulse light signal is reflected at the third four-port polarization beam splitter PBS 3120 back to the 50:50 beam splitter BS 50:50 beam splitter 113. This process can be expressed as:

[0072]

[0073] Similarly, the single photon pulses of the second optical path pass through the opposite path. The single photon pulses of the second optical path do not modulate the phase when passing through the third SC device 122. After that, the polarization direction changes by 90°. Similarly, these pulses pass through the first optical path to reach Bob 1. The pulse light signal loads the phase φ B (0 or π) at Bob 1 and then returns to the 50:50 beam splitter BS 113. This process can be expressed as:

[0074]

[0075] Finally, the two paths of pulses interfere at a 50:50 beam splitter BS 113:

[0076]

[0077] If the phase difference between φ B1 and φ A is 0 or 2π, the first single-photon detector D1124 responds; if the phase difference between φ B1 and φ A is π, the second single-photon detector D2125 responds.

[0078] Similarly, if Alice wants to share a string of secure keys with Bob2, the polarized modulation module is used to make the polarized state of the pulse optical signal |A> first. Alice and Bob2 modulate the corresponding second SC device 117 to load the phase, and the process of sharing the keys is similar to that of Alice and Bob1. This process can be represented by the following formula:

[0079]

[0080] Similarly, if the phase difference between φ B2 and φ A is 0 or 2π, the first single-photon detector D1124 responds; if the phase difference between φ B2 and φ A is π, the second single-photon detector D2125 responds.

[0081] Specifically, in the foregoing process, the expressions of the horizontal polarization H and vertical polarization V pulse optical signals at different stages are as follows:

[0082] The horizontal polarization state |H> and the vertical polarization state |V> of the horizontal polarization H and vertical polarization V parts are represented by the Jones matrix as follows:

[0083]

[0084] The vertical polarization state |V> introduces an additional phase of π / 2 after being reflected by the first polarized beam splitter PBS1, and the Jones matrix representation of the first Faraday rotator FR1108 is as follows:

[0085]

[0086] The horizontal polarization state |H> after passing through the first Faraday rotator FR1 is represented as follows:

[0087]

[0088] Then, the horizontal polarization state |H> passes through the first phase modulator PM1107 without any modulation at the first phase modulator PM1107, and is input to the first polarization beam splitter PBS1106 to be reflected back to the first CIR ring 105, and the horizontal polarization state |H> is obtained as:

[0089]

[0090] Similarly, the pulse of the vertical polarization state |V> first passes through the first phase modulator PM1107 to be loaded with a phase △φ, and becomes:

[0091]

[0092] Then, the pulse of the vertical polarization state |V> after being combined at the first polarization beam splitter PBS1106 can be expressed as:

[0093]

[0094] The utility model discloses be provided with phase encoder and gradually set multiple polarization encoders to modulate the pulse light signal signal, and phase encoder has higher anti-interference ability to environmental noise and interference, guarantees the stability and reliability of signal, realizes strong anti-interference ability.

[0095] The multiple polarization encoders are used to adjust the pulse light signal signal into the polarization state selected by the user, so that different users can independently communicate on the same quantum channel, greatly improve the flexibility of user selection, and improve the flexibility and expansibility.

[0096] According to the disclosure and teaching of the above description, the skilled in the art of the utility model can also change and modify the above embodiment. Therefore, the utility model is not limited to the specific embodiments disclosed and described above, and some modifications and changes of the utility model should fall within the protection scope of the claims of the utility model. In addition, although some specific terms are used in the specification, these terms are only for convenience of description and do not constitute any limitation on the utility model.

Claims

1. A dynamic user phase encoding quantum communication system, characterized by, The system comprises a LD laser LD, a first CIR circulator, a first SC device, a first polarization controller PC1, a polarization modulation module, a second CIR circulator, an intensity modulator IM, an attenuator ATT, a third CIR circulator, a detection unit, a 50:50 beam splitter BS, a second polarization controller PC2, a second four-port polarization beam splitter PBS2, a second delay line DL, a second SC device, a first receiving end Bob1, a third polarization controller PC3, a third four-port polarization beam splitter PBS3, a third delay line DL, and a third SC device, wherein: The laser LD is used to generate an initial pulsed optical signal; The first CIR circulator transmits the initial pulsed optical signal to the first SC device and the first polarization controller PC1; said first SC device is configured to modulate an initial phase φ of said initial pulsed light signal A ∈ {0, π / 2, π, 3π / 2}; The first polarization controller PC1 is used to modulate the initial pulsed optical signal into a 45° polarization state; The polarization modulation module is used to load a phase and adjust a polarization state of the 45° polarization state pulsed optical signal into a horizontal polarization state; The intensity modulator IM is used to modulate the pulsed optical signal into a signal state or a decoy state pulse; The attenuator ATT attenuates the pulsed optical signal to a single-photon level; The 50:50 beam splitter BS is used to divide the pulsed optical signal into a first beam and a second beam; The first beam passes through the second four-port polarization beam splitter PBS2 to reach the selected user end Bob1, and returns to the original route after modulation at the user end Bob1; The second beam passes through the third four-port polarization beam splitter PBS3 to reach the selected user end Bob2, and returns to the original route after modulation at the user end Bob2; When the returned first beam and second beam reach the 50:50 beam splitter BS at the same time, they are transmitted to the detection unit after passing through the third CIR circulator for detection.

2. A dynamic user phase encoding quantum communication system as claimed in claim 1, wherein, The polarization modulation module comprises a first polarization beam splitter PBS1, a first phase modulator PM1, a first Faraday rotator FR1, and a first delay line DL; An input port of the first polarization beam splitter PBS1 is connected to the first CIR circulator through an optical signal; one output port of the first polarization beam splitter PBS1 is connected to the first Faraday rotator FR1 through the first delay line DL; Another output port of the first polarization beam splitter PBS1 is connected to the first phase modulator PM1 through an optical signal; The first phase modulator PM1 is connected to the first Faraday rotator FR1 through an optical signal.

3. A dynamic user phase encoding quantum communication system as claimed in claim 2, wherein, The detection unit comprises a first single-photon detector D1 and a second single-photon detector D2.

4. A dynamic user phase encoding quantum communication system as claimed in claim 3, wherein, After the first polarization controller PC1 adjusts the initial pulsed optical signal into a 45° polarized pulsed optical signal, the 45° polarized pulsed optical signal is divided into a horizontal polarized pulse H and a vertical polarized pulse V with the same probability after being sent to the first polarization beam splitter PBS1; The horizontal polarized pulse transmits through the first polarization beam splitter PBS1; The vertical polarization pulse first passes through the first phase modulator PM1 to load phase △φ, and then passes through the first Faraday rotator FR1 and the first delay line DL to become a horizontal polarization state, and then transmits through the first polarization beam splitter PBS1 to return to the first CIR circulator R.

5. A dynamic user phase encoding quantum communication system as claimed in claim 4, wherein, The vertical polarization state |V> of the vertical polarization pulse V introduces an additional phase of π / 2 after being reflected by the first polarization beam splitter PBS1; The horizontal polarization state |H> of the horizontal polarization pulse passes through the first Faraday rotator FR1 and is reflected at the first polarization beam splitter PBS1 to return to the first CIR circulator.

6. A dynamic user phase encoding quantum communication system as claimed in claim 5, wherein, The pulse of the vertical polarization state |V> first passes through the first phase modulator PM1 to load phase △φ, and then the vertical polarization state |V> is combined with the horizontal polarization state |H> at the first polarization beam splitter PBS1, and the combined pulse after combination is transmitted to the intensity modulator IM.

7. A dynamic user phase encoding quantum communication system as claimed in claim 6, wherein, The intensity modulator IM modulates the combined pulse optical signal into a signal state or a decoy state pulse, and then transmits it to the attenuator ATT, which attenuates the signal state or the decoy state pulse to a single photon level to obtain a single photon pulse.

8. A dynamic user phase encoding quantum communication system as claimed in claim 7, wherein, The single photon pulse passes through the third CIR circulator to reach the 50:50 beam splitter BS113, and the single photon pulse output from the 50:50 beam splitter BS113 is divided into two light paths, the first light path and the second light path, and the single photon pulses of the first light path and the second light path pass through the second four-port polarization beam splitter PBS2 and the third four-port polarization beam splitter PBS3 respectively to reach the corresponding selected user terminals Bob1 and Bob2.

9. A dynamic user phase encoding quantum communication system as claimed in claim 8, wherein, The horizontal polarization state |H> and the vertical polarization state |V> are represented by a Jones matrix:

10. The dynamic user phase encoding quantum communication system of claim 9, wherein, The vertical polarization state |V> introduces an additional phase of π / 2 after being reflected by the first polarization beam splitter PBS1, and the Jones matrix representation of the first Faraday rotator FR1 is: The horizontal polarization state |H> after passing through the first Faraday rotator FR1 is represented as:

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