Photon flow coincidence communication method

Abstract

The invention relates to a photon flow coincidence communication method, and belongs to the technical field of quantum communication. According to the method, an entangled photon source continuously outputs polarized entangled photon pairs to form two paths of photon flows, and one path of photon flows is sent to a receiving end through an optical path 1 and then is transmitted to a detector A through a polarizer A and a delayer; the other path is sent to a sending end through a light path 2, sending information is transmitted to a detector B of a receiving end through a light path 3 after the photon flow is polarized and modulated through a polarizer B, coincidence counting is carried out on entangled photons detected by the detector A and the detector B based on the non-localized correlation and unclonable characteristics of quantum entanglement, a large number or a small number represents a numerical value 1 or a numerical value 0, and the number of the large number or the small number represents a numerical value 0; therefore, the received information is obtained. The photon flow in the method does not carry information, so that the method has the advantages of principle safety; the method avoids technical obstacles in links of single photon generation, transmission, operation, relaying, time synchronization and the like in a single photon communication method, so that the method is easy to implement.

Description

Technical Field

[0001] The present invention belongs to the technical field of quantum communication, and in particular relates to a photon stream coincidence communication method. Background Art

[0002] Quantum communication, based on the non-cloning principle and non-local correlation properties of quantum entanglement, offers the principle advantage of absolute security. Since the proposal of the first quantum communication scheme, the BB84 protocol, in 1984, research on quantum communication theory and methods has remained at the forefront of global science and technology.

[0003] The existing quantum communication methods mainly include quantum key distribution based on the BB84 protocol, quantum direct communication and quantum teleportation.

[0004] Quantum key distribution includes measurement device-independent quantum key distribution and dual-field quantum key distribution. This method is based on single-photon manipulation and does not utilize the non-cloning principle and non-local correlation characteristics of quantum entanglement. Therefore: (1) It does not have the principle advantage of absolute security of quantum communication; (2) It requires a single-photon source, which is currently unavailable in the world; (3) It requires absolute time synchronization of all nodes in the entire network, which is difficult to achieve in theory and practice; (4) It requires complex and expensive technologies and equipment, such as laser frequency stabilization and ultra-stable optical frequency synchronization technology for light sources, high-bandwidth channel phase compensation technology, and high signal-to-noise ratio single-photon detection signal discrimination technology, resulting in low transmission rate and high bit error rate.

[0005] Quantum direct communication is also based on single-photon manipulation and does not utilize the non-cloning principle and non-local correlation characteristics of quantum entanglement. Therefore, it has the same principles and technical defects as quantum key distribution communication methods.

[0006] Quantum teleportation utilizes the non-cloning principle and non-local correlation characteristics of quantum entanglement, and therefore has the principle advantage of absolute security of quantum communication. However, it has not yet been realized because it is difficult to overcome the technical barriers in the generation, transmission, operation, relay and storage of single photons. Summary of the Invention

[0007] The purpose of the present invention is to provide a photon stream coincidence communication method (Photon Stream Coincidence Communications, PSCC), which utilizes the non-cloning principle and non-local correlation characteristics of quantum entanglement and has the "principle security" advantage of quantum communication.

[0008] To achieve the above object, the technical solution of the present invention is: a photon stream conforming communication method PSCC, the working principle of PSCC is as follows Figure 1As shown: the entangled photon source continuously outputs polarization entangled photon pairs to form two photon streams, one of which is sent to the receiving end via optical path 1, and then transmitted to detector A after passing through polarizer A and delay device; the other is sent to the transmitting end via optical path 2, and the transmitted information is polarized by polarizer B to modulate the photon stream and then transmitted to detector B at the receiving end via optical path 3. Based on the non-local correlation and non-cloning characteristics of quantum entanglement, the entangled photons detected by detectors A and B are counted, and the large or small number represents the value 1 or the value 0, thereby obtaining the received information.

[0009] The method of modulating the polarization direction of the photon flow through polarizer B to send information is: setting the polarization direction of polarizer A to 0° and the polarization direction of polarizer B to β, so that the coincidence count value is a large number m; keeping the polarization direction of polarizer A unchanged, adjusting the polarization direction of polarizer B to θ, so that the coincidence count value is a small number n; usually m>>n; large numbers represent the value 1 or 0, and small numbers represent the value 0 or 1. According to the binary code to be sent, the polarization direction of polarizer B is changed between (β, θ) to realize information transmission.

[0010] The principle security of PSCC is manifested in two aspects:

[0011] The optical path carries no information. The number of photons with H polarization in optical path 1 or optical path 2 is equal to the number of photons with V polarization, meaning 50% of the photons are H polarized and 50% are V polarized. Changing the polarization direction of polarizer A or polarizer B does not increase or decrease the number of photons in the optical path, nor does it change the light intensity in the optical path. For example, if the polarization direction of polarizer B changes by any angle α, Sin2α + Sin2(90° - α) = Sin2α + Cos2α = 1. Because the number of photons in the optical path is constant, and a single photon does not exhibit entanglement, optical paths 1, 2, and 3 carry no information.

[0012] "Hand-to-hand" information transmission. The received information is obtained by counting the coincidences of the entangled photons detected by detectors A and B. Detectors A, B, coincidence counting, and received information are all located at the receiving end, thus achieving "hand-to-hand" information transmission.

[0013] like Figure 1 As shown, the receiving end is above the dotted line BB. The communication unit at the receiving end includes an entangled photon source, polarizer A, and a delay device. The delay device ensures that the entangled photon pair arrives at detectors A and B at approximately the same time, as shown by the dotted line AA.

[0014] The above scheme is applicable to both optical fiber and satellite communications. A type-II spontaneous parametric down-conversion polarization-entangled photon source can be used to achieve higher transmission power while also avoiding the attenuation and noise of the optical fiber channel, resulting in better communication performance.

[0015] Compared to existing technologies, the present invention has the following advantages: The present invention and its preferred embodiment have low requirements for light sources and channels, making them easy to implement. They can be used for dedicated line communications, such as confidential lines or private networks for governments, military forces, public security, and enterprises, and data transmission between remote data centers. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 For the present invention Figure 1 It is a schematic diagram of a technical embodiment of the photon flow communication method of the present invention.

[0017] These include: entangled photon source, optical path 1, optical path 2, optical path 3, polarizer A, polarizer B, delay device, detector A, detector B, coincidence counting, information sending, information receiving and other units. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0019] It should be noted that the following detailed descriptions are all exemplary, and unless otherwise specified, the technical and scientific terms used in the following descriptions have the same meanings as commonly understood by those of ordinary skill in the art to which this application belongs.

[0020] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] The specific technical solution of the photon stream conformance communication method PSCC of the present invention is as follows:

[0022] like Figure 1 As shown: The entangled photon source continuously outputs polarization entangled photon pairs, and their entanglement characteristics are manifested as the polarization direction of the entangled photon pair. That is, if the polarization direction of one photon is horizontal (H), the polarization direction of the other photon must be vertical (V), and vice versa. The polarization state of the entangled photon pair constitutes the entangled state of the quantum bit, which is manifested as the entangled correlation of the photon pair:

[0023]

[0024] Introducing into formula (1) Figure 1 The entangled correlation of the photon pairs in detectors A and B is:

[0025]

[0026] Where H corresponds to the polarization direction of polarizer A and polarizer B is 0°, V corresponds to the polarization direction of polarizer A and polarizer B is 90°, and the coincidence count H direction is set to + and V direction is set to -, then formula (2) is expressed as:

[0027]

[0028] Therefore, the coincidence count measured by the coincidence counting unit under the basis vectors |+>A|->B and |->A|+>B is a maximum value, and the coincidence count measured under the basis vectors |+>A|+>B and |->A|->B is a minimum value. By changing the polarization direction of polarizer A or polarizer B between 0° and 90°, a coincidence count value between the maximum value and the minimum value is obtained.

[0029] The polarization-entangled photon pairs continuously output by the entangled photon source form two photon streams. One stream is sent to the receiver via optical path 1, then transmitted to detector A via polarizer A and a delay element. The other stream is sent to the transmitter via optical path 2. The polarization direction of the photon stream is modulated by polarizer B, and then transmitted to detector B at the receiver via optical path 3. Based on the nonlocal correlation and non-cloning properties of quantum entanglement, the entangled photons detected by detectors A and B are counted by coincidence, with larger or smaller numbers representing the value 1 or 0, thereby obtaining the received information.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

[0031] This patent is not limited to the above-mentioned best implementation mode. Anyone can derive other forms of photon flow conforming communication methods based on the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of this invention should be covered by this patent.

Claims

1. A photon flow coincidence communication method, characterized in that: The entangled photon source continuously outputs polarization entangled photon pairs to form two photon streams. One stream is sent to the receiving end via optical path 1, and then transmitted to detector A after passing through polarizer A and delay device; the other stream is sent to the transmitting end via optical path 2. The transmitted information is polarized and modulated by polarizer B, and then transmitted to detector B at the receiving end via optical path 3. Based on the non-local correlation and non-cloning characteristics of quantum entanglement, the entangled photons detected by detectors A and B are counted by coincidence. The large or small number represents the value 1 or the value 0, thereby obtaining the received information.

2. A photon flow coincidence communication method according to claim 1, characterized in that: The method of modulating the polarization direction of the photon flow through polarizer B to send information is: setting the polarization direction of polarizer A to 0° and the polarization direction of polarizer B to β, so that the coincidence count value is a large number m; keeping the polarization direction of polarizer A unchanged, adjusting the polarization direction of polarizer B to θ, so that the coincidence count value is a small number n; usually m>>n; large numbers represent the value 1 or 0, and small numbers represent the value 0 or 1. According to the binary code to be sent, the polarization direction of polarizer B is changed between (β, θ) to realize information transmission.

3. The photon flow coincidence communication method according to claim 1, characterized in that: The optical path does not carry information. The number of photons with H polarization in optical path 1 or optical path 2 is equal to the number of photons with V polarization, that is, 50% of the photons are with H polarization and 50% of the photons are with V polarization. Changing the polarization direction of polarizer A or polarizer B does not increase or decrease the number of photons in the optical path, that is, it does not change the light intensity in the optical path. When the polarization direction of polarizer B changes by any angle α, Sin 2 α+Sin 2 (90°-α)=Sin 2 α+Cos 2 α=1; since the number of photons in the optical path is constant and a single photon does not exhibit entanglement characteristics, optical path 1, optical path 2, and optical path 3 do not carry any information.

4. The photon flow coincidence communication method according to claim 1, characterized in that: The received information is obtained by counting the coincidences of the entangled photons detected by detectors A and B. Detector A, detector B, coincidence counting, and received information are all placed at the receiving end, thus achieving "hand-to-hand" information transmission.

5. The photon flow coincidence communication method according to claim 1, characterized in that: The communication unit placed at the receiving end includes an entangled photon source, a polarizer A, and a delay device; the function of the delay device is to ensure that the entangled photon pair reaches detectors A and B at the same time.

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