Bit encoding method for quantization protocol of continuous variable quantum key distribution system

Abstract

This invention proposes a bit encoding method for quantization protocols in continuous-variable quantum key distribution systems, relating to the field of quantum secure communication. The method first selects the number of bits corresponding to each quantum signal in the binary information, then constructs a binary information sequence iteratively, and finally outputs the bit-encoded sequence. This method ensures that the bit codes of adjacent intervals in the quantization protocol of a continuous-variable quantum key distribution system differ by only one bit, reducing bit encoding errors caused by crosstalk between adjacent intervals of the quantum signal.

Description

Technical Field

[0001] The present invention relates to the field of quantum information science, and in particular to a bit encoding method for a quantization protocol in a continuous variable quantum key distribution system. Background Art

[0002] Quantum Key Distribution (QKD) is a method of distributing keys through quantum channels using photon states as information carriers. The two communicating parties (Alice and Bob) complete the secure transmission of information by sharing an unconditionally secure key. The basic principles of quantum mechanics and the data security processing protocol of classical information theory guarantee the unconditional security of quantum keys.

[0003] The two most common schemes in quantum key distribution systems are discrete variable quantum key distribution (DVQKD) and continuous variable quantum key distribution (CVQKD). Compared with DVQKD, CVQKD has the advantages of being universal with classical optical communication equipment, high coding rate and low construction cost. It has great potential in the future quantum network construction, confidential and secure communication and other fields. DVQKD loads quantum keys by modulating the polarization, phase and other physical quantities of photons, and the detection results are discrete variables, while CVQKD uses Gaussian modulation to detect the position coordinates of coherent state light or compressed state light. x and momentum coordinates p After the quantum key is loaded, the detection result is a continuous variable. In order to obtain the key that the two communicating parties ultimately share, the detected quantum signal needs to be converted into a binary key. To this end, the detection results that may be produced by the quantum signal need to be divided into several intervals, and each interval is set with a corresponding binary key (i.e., bit encoding), and the binary key represented by the detection result of the quantum signal is determined according to the interval in which it is located.

[0004] However, due to the influence of detection errors and other factors, quantum signals may crosstalk to adjacent intervals after transmission, resulting in transmission errors of binary keys. Therefore, a bit encoding method is needed that can minimize the difference between binary keys corresponding to adjacent intervals, so as to minimize the error of the final key result. Summary of the invention

[0005] In response to the optimization requirements of the bit encoding method in the above-mentioned continuous variable quantum key distribution system, the present invention proposes a bit encoding method for the quantization protocol of the continuous variable quantum key distribution system, which can reduce the binary coding errors caused by crosstalk between quantum signals in adjacent intervals.

[0006] To achieve the above object, the technical solution adopted by the present invention is:

[0007] A bit encoding method for a quantization protocol of a continuous variable quantum key distribution system comprises the following steps:

[0008] Step 1: Bob receives the binary information corresponding to the detected quantum signal. n Make a selection, then the number of interval divisions in the quantization protocol is N =2 n ;

[0009] Step 2: Set the iteration variable k ,make k = n ; Set the length of the binary information sequence to M =2 1 =2, the binary information sequence is [0, 1];

[0010] Step 3, if k =1, then the current binary information sequence is output, which is N =2 n The bit encoding sequence corresponding to the interval ends the process; if k >1, then execute steps 4 and 5;

[0011] Step 4: copy and expand the binary information sequence. The length of the expanded sequence is 2 M , in the expanded sequence, the elements in the odd positions are exactly the elements in the original binary information sequence, and the elements in the even positions copy the previous odd-numbered elements;

[0012] Step 5, add a last bit to each element of the expanded sequence, where the added last bit is the element of the corresponding position in the cyclic sequence of "0, 1, 1, 0";

[0013] Step 6, Update k = k -1, M =2 M , return to step 3.

[0014] Furthermore, the quantum signal received by Bob in step 1 is a Gaussian modulated signal, and the quantum signal is coherent state light or compressed state light.

[0015] Furthermore, the physical quantity modulated by the Gaussian modulated signal is the position coordinate of the coherent state light or the compressed state light. X or momentum coordinates P .

[0016] Furthermore, in step 1, Bob's detection method is coherent detection, and the physical quantity detected is the position coordinate X or momentum coordinates P .

[0017] The beneficial effects of the present invention are:

[0018] 1. The method of the present invention is simple and easy to implement.

[0019] 2. The method of the present invention can make the bit codes corresponding to adjacent divided intervals differ by 1 bit, and the coding error caused by crosstalk of each signal to the adjacent interval due to detection error is 1 bit, thereby reducing the binary coding error caused by crosstalk of quantum signals in adjacent intervals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The schematic diagram of the bit coding expansion in the embodiment of the present invention shows n arrive n +1 bit encoding recursion process.

[0021] Figure 2 Schematic diagram of dividing the Gaussian modulated quantum signal into intervals in an embodiment of the present invention, showing different bit numbers n The interval division method under bit encoding. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described in more detail below in conjunction with the accompanying drawings and embodiments.

[0023] A bit encoding method for a quantization protocol in a continuous variable quantum key distribution system, the specific steps are as follows:

[0024] Step 1: Bob receives and detects the number of bits of binary information corresponding to the quantum signal. n Make a selection, and the number of interval divisions in the quantization protocol is N =2 n ;

[0025] The quantum signal received by Bob is a Gaussian modulated signal. Furthermore, the quantum signal is an optical signal, usually a coherent state light or a compressed state light. The physical quantity modulated by the Gaussian modulation is the position coordinate of the coherent state light or the compressed state light. x or momentum coordinates p .

[0026] Bob's detection method is coherent detection, usually homodyne detection or heterodyne detection. Furthermore, the physical quantity detected by Bob is the position coordinates mentioned above. x or momentum coordinates p .

[0027] Step 2: Determine the value selected in step 1 n Is it 1? n =1, the number of interval divisions in the quantization protocol isN =2 1 =2, let the binary information sequence corresponding to these two intervals be [0, 1];

[0028] Step 3 (copy expansion step): When n =2, for n =1, the binary information in the binary information sequence corresponding to each interval is copied and expanded, that is, the binary information sequence corresponding to each interval is expanded from [0, 1] to [0, 0, 1, 1];

[0029] Step 4 (adding the last bit): In the expanded binary information sequence, add "0, 1, 1, 0" to the end of each binary information in the sequence until all the binary information in the sequence has finished adding the last bit. That is, the final result of the binary information sequence is [00, 01, 11, 10]. This result is n =2, the binary information sequence corresponding to each interval;

[0030] Step 5: Repeat steps 3 to 4 until n The corresponding bit encoding method is extended to n +1, by recursion, we can get any n >1, the bit encoding corresponding to each interval.

[0031] Any n When >1, the bit codes corresponding to each interval have the following characteristics: the bit codes corresponding to adjacent divided intervals differ by 1 bit. Furthermore, the coding error caused by the crosstalk of each signal to the adjacent interval due to the detection error is 1 bit.

[0032] This method can reduce binary coding errors caused by crosstalk between quantum signals in adjacent intervals, and minimize binary key errors caused by detection signals entering adjacent intervals due to errors.

[0033] Figure 1 The process of bit-coded expansion is described, which expands the sequence [0, 1] to the sequence [000, 001, 011,010, 110, 111, 101, 100].

[0034] Figure 2 Schematic diagram of the interval division of Gaussian modulated quantum signal. Specifically, Figure 2 (a) indicates n =1 interval division diagram, Figure 2 (b) indicates n =2, the horizontal axis is the position coordinate of the quantum signal x or momentum coordinatesp The vertical axis is the size of the detected x or p The probability density of , further, its probability distribution is Gaussian distribution.

[0035] The above description is only a specific implementation of the present invention in the embodiment, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A bit encoding method for a quantization protocol of a continuous variable quantum key distribution system, characterized in that: The following steps are involved: Step 1: Bob receives the binary information corresponding to the detected quantum signal. n Make a selection, then the number of interval divisions in the quantization protocol is N =2 n ; Step 2: Set the iteration variable k ,make k = n ; Set the length of the binary information sequence to M =2 1 =2, the binary information sequence is [0, 1]; Step 3, if k =1, then the current binary information sequence is output, which is N =2 n The bit encoding sequence corresponding to the interval ends the process; if k >1, then execute steps 4 and 5; Step 4: copy and expand the binary information sequence. The length of the expanded sequence is 2 M , in the expanded sequence, the elements in the odd positions are exactly the elements in the original binary information sequence, and the elements in the even positions copy the previous odd-numbered elements; Step 5, add a last bit to each element of the expanded sequence, where the added last bit is the element of the corresponding position in the cyclic sequence of "0, 1, 1, 0"; Step 6, Update k = k -1, M =2 M , return to step 3.

2. The bit encoding method for the quantization protocol of the continuous variable quantum key distribution system according to claim 1, characterized in that: The quantum signal received by Bob in step 1 is a Gaussian modulated signal, and the quantum signal is coherent state light or compressed state light.

3. The bit encoding method for the quantization protocol of the continuous variable quantum key distribution system according to claim 2, characterized in that: The Gaussian modulated signal modulates the position coordinates of the coherent state light or the compressed state light. X or momentum coordinates P .

4. The bit encoding method for the quantization protocol of the continuous variable quantum key distribution system according to claim 3 is characterized in that: In step 1, Bob's detection method is coherent detection, and the physical quantity detected is the position coordinate X or momentum coordinates P .

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