Quantum time synchronization method for power system

Abstract

The present invention proposes a method for quantum time synchronization of power systems, the principle of which is based on the non-local correlation characteristics and decoherence characteristics of quantum entanglement, the use of optical fiber channels to realize the transmission of entangled photon streams, and the use of ultrafast optoelectronic devices to realize the controllable decoherence of entangled photons, thereby achieving time synchronization.

Description

Technical Field

[0001] The invention belongs to the technical field of time and frequency, and in particular relates to a quantum time synchronization method for a power system. Background Art

[0002] The production and operation, dispatching management, and protection and control of the power system are all strongly related to time. Whether each link can be strictly and accurately synchronized is directly related to the safety, reliability, and stability of the system operation. The time synchronization method of the power system is mainly based on the (space-based) synchronization method of navigation satellites. Other methods such as synchronization methods based on network protocols, wide-area time synchronization methods combining satellite clocks with network clocks, and wired (ground-based) synchronization methods of precise clock sources are still in the research and exploration stage.

[0003] The time synchronization method based on GPS / Beidou navigation satellites is time source synchronization, which is easy to use, highly accurate, and has a synchronization error of less than 0.1 microseconds, which can meet the requirements of relevant standards and regulations. However, its shortcomings are also very prominent, including: 1) The receiving device has high requirements on the strength of the satellite signal, and the reception effect is poor in severe weather conditions, indoor environments, and places where it is inconvenient to set up antennas, and the timing accuracy is unstable. 2) The synchronization error reaches tens or even hundreds of milliseconds when the signal is lost. 3) Poor security. The civilian signals of navigation satellites lack an encryption and authentication mechanism, and the signals are easily forged, resulting in synchronization time errors. The satellite navigation system is vulnerable to attack in a war environment. 4) The electromagnetic radiation of high-voltage transmission lines and power plants (stations) interferes with the satellite reception signal, affecting the timing accuracy and reliability, etc.

[0004] The synchronization methods based on the simple network time protocol and the IEEE1588 precision time protocol have errors of the former in the sub-second range and the latter in less than 0.4 milliseconds, which cannot meet the synchronization accuracy requirements of line traveling wave fault ranging, synchronous phasor measurement and lightning location. The wide-area time synchronization method combining satellite clocks and network clocks is based on the "space-based" time synchronization of navigation satellites and supplemented by the "ground-based" time synchronization of the precise clock source of the dispatching center, forming a "space-earth mutual backup" time synchronization system. Theoretically, the synchronization error is less than ±10 nanoseconds. However, considering the complexity of the wide-area system structure, its actual effect remains to be verified. It should be emphasized that the above methods all rely on the navigation satellite clock source, and it is difficult to avoid the many disadvantages of navigation satellite time synchronization. Summary of the invention

[0005] In view of the defects and shortcomings of the prior art, the present invention proposes a quantum time synchronization method based on the theory of quantum entangled states. The principle is to use optical fiber channels to realize the transmission of entangled photon streams based on the non-local correlation characteristics and decoherence characteristics of quantum entanglement, and to use ultrafast optoelectronic devices to realize the controllable decoherence of entangled photons, thereby achieving time synchronization.

[0006] The specific scheme is: the polarization entangled photon pair is output through the all-fiber polarization entangled photon source, one of which enters the optical fiber channel and is sent to the other end, and the time synchronization signal is obtained through collimation, polarization detection and photoelectric detection; the other enters the local optical path in spatial light mode, and annihilates itself after collimation, adjustable delay, optical switch, and λ / 2 wave plate. The standard clock unit controls the connection and disconnection of the optical switch, so that the entangled photon is in a given time window ΔT 0 After passing through the optical fiber channel, the polarization direction of the photon changes by an angle Δv after being modulated by the λ / 2 wave plate. Based on the non-local correlation characteristics of quantum entanglement, the polarization angle of the entangled photon at the opposite end changes by Δv at the same time. The function of the adjustable delay device is to compensate for the time delay of the optical fiber channel to ensure the effectiveness of the optical switch and the λ / 2 wave plate. The polarization axis of the polarizer at the opposite end is set so that the light intensity detected by the photoelectric detection unit is the minimum when v=0 and the light intensity is the maximum when v=-Δv. The time window of maximum light intensity is ΔT 1 When ΔT 1 =ΔT and the step difference between the clock to be synchronized and the standard clock is 0, the clocks at both ends are synchronized.

[0007] The technical solution adopted by the present invention to solve the technical problem is:

[0008] A method for quantum time synchronization of a power system, characterized by:

[0009] The polarization entangled photon pair is output through the all-fiber polarization entangled photon source. One of them enters the optical fiber channel and is sent to the other end. After collimation, polarization detection and photoelectric detection, a time synchronization signal is obtained; the other enters the local optical path in spatial light mode and is annihilated after collimation, adjustable delay device, optical switch and λ / 2 wave plate.

[0010] The standard clock unit controls the on and off of the optical switch, so that the entangled photons are in a given time window ΔT. 0 After passing through the inner part, the polarization direction of the photon changes by an angle Δv after being modulated by the λ / 2 wave plate. Based on the non-local correlation characteristics of quantum entanglement, the polarization angle of the entangled photon at the opposite end also changes by Δv.

[0011] Set the polarization axis of the polarizer at the opposite end so that the light intensity detected by the photoelectric detection unit is minimum when v=0 and maximum when v=-Δv. Then the time window of maximum light intensity is ΔT 1 ; When ΔT 1 =ΔT and the step difference between the clock to be synchronized and the standard clock is 0, the clocks at both ends are synchronized.

[0012] Furthermore, the function of the adjustable delay device is to compensate for the time delay of the optical fiber channel so that when the entangled photon reaches position A in the optical path at this end, it reaches position A' in the optical path at the other end, so as to ensure the effectiveness of the optical switch and the λ / 2 wave plate; A-A' connects the optical path before position A with the optical path after position A' through the non-local correlation of quantum entanglement, forming a complete optical path.

[0013] Compared with the prior art, the present invention and its preferred solution can avoid many drawbacks of navigation satellite time synchronization, and are not affected by network delay differences and connection methods. A clock source + optical fiber channel can achieve autonomous time synchronization of dispatching agencies or substations (power plants). Quantum entanglement is not affected by electromagnetic interference and is very adaptable to the strong electromagnetic environment of the power system. Based on existing product-level ultrafast optoelectronic devices, sub-picosecond synchronization accuracy can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0015] Figure 1 This is a schematic diagram of the implementation principle of quantum time synchronization according to an embodiment of the present invention;

[0016] Figure 2 This is a schematic diagram of the quantum time synchronization principle of an embodiment of the present invention;

[0017] Figure 1 Among them, 1 is an all-fiber polarization entangled photon source, 2 is an optical fiber channel, 3 is a first collimator, 4 is an analyzer, 5 is a photodetector, 6 is a second collimator, 7 is an adjustable delay device, 8 is an optical switch, and 9 is a λ / 2 wave plate. DETAILED DESCRIPTION

[0018] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

[0019] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meanings as those commonly understood by those skilled in the art to which the present 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, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0021] like Figure 1 As shown, in the scheme provided by the embodiment of the present invention, the all-fiber polarization entangled photon source 1 outputs polarization entangled photon pairs, one of which enters the optical fiber channel 2 and is sent to the other end, and obtains a time synchronization signal through the first collimator 3, the polarization analyzer 4 and the photoelectric detector 5; the other enters the local optical path in a spatial light mode, and annihilates itself after passing through the second collimator 6, the adjustable delay 7, the optical switch 8, and the λ / 2 wave plate 9. The function of the adjustable delay is to compensate for the time delay of the optical fiber channel so that when the entangled photons reach position A in the local optical path, they reach position A' in the opposite optical path to ensure that the optical switch and the λ / 2 wave plate are effective. In other words, A-A' connects the optical path before A and the optical path after A' together through the non-local correlation of quantum entanglement to form a complete optical path. The standard clock unit controls the connection and disconnection of the optical switch, so that the entangled photons are in a given time window ΔT. 0 After passing through the λ / 2 wave plate, the polarization direction of the photon changes by an angle Δθ. Based on the non-local correlation characteristics of quantum entanglement, the polarization angle of the entangled photon at the opposite end changes by Δθ at the same time. The polarization axis of the analyzer is set so that the light intensity detected by the photoelectric detection unit is the minimum when θ=0 and the light intensity is the maximum when θ=-Δθ. The time window of maximum light intensity is ΔT 1 When the clocks at both ends are synchronized, ΔT 1 =ΔT 0 ; When the clocks at both ends are not synchronized, ΔT 1 <ΔT 0 .

[0022] The feasibility of the principle of the solution of this embodiment is demonstrated below based on the characteristics of quantum entanglement and Jones matrix.

[0023] The two-photon polarization entangled state generated by the polarization entangled photon source is:

[0024]

[0025] Where H and V represent horizontal polarization and vertical polarization respectively. Represents the phase difference between horizontal polarization and vertical polarization.

[0026] When the optical switch of the local optical path is turned on, the entangled photon rotates a set angle Δθ after being modulated by the λ / 2 wave plate, and the polarization angle of the entangled photon at the other end changes by Δθ at the same time. At this time, the phase between the entangled photon pair is α:

[0027]

[0028] At this time, the two-photon polarization entangled state is:

[0029]

[0030] The photoelectric detection at the other end is equivalent to decoherence operation on the polarization state of the photon, resulting in collapse of the entangled state. There is a 50% probability of collapse to the |H> state and a 50% probability of collapse to the |V> state, that is:

[0031]

[0032] Set the polarization axis of the polarizer at the opposite end so that the light intensity detected by the photoelectric detection unit is the maximum based on the |V> state, then:

[0033]

[0034] The on-time of the optical switch controlled by the standard clock unit at this end is ΔT, and the duration of the maximum light intensity detected by the photoelectric detection unit at the other end is ΔT 1 When the time at both ends is synchronized, there is ΔT 1 =ΔT; when the time at both ends is not synchronized, there is ΔT 1 <ΔT.

[0035] The optical model of the present invention is as follows:

[0036] The entangled photon source outputs linearly polarized light, and the Jones matrix is:

[0037]

[0038] If the angle of the polarization axis of the analyzer is set to β, the intensity of the linearly polarized light after polarization analysis is:

[0039]

[0040] When the optical switch at this end is turned on, the linearly polarized light at the other end is deflected by Δθ, and the outgoing light intensity is:

[0041]

[0042] Assuming β = 90°, when the optical switch is turned off, Δθ = 0, the output light intensity is obtained according to formula (9):

[0043]

[0044] At this time, the light intensity detected by the photoelectric detection unit is the minimum. When the optical switch is turned on:

[0045] I o =I i cos 2 (β+Δθ)=Iisin 2 Δθ (10)

[0046] The light intensity detected by the photoelectric detection unit is the maximum.

[0047] In addition, the time synchronization method of this embodiment is as follows:

[0048] Time t can be expressed by a linear function: f(t)=a+bt, where a is the origin difference between the standard clock and the clock to be synchronized, and a=0 means that the time reported by the clocks at both ends is consistent; b is the unit time interval difference between the clocks at both ends, that is, the clock to be synchronized runs faster (b>1) or slower (b<1) than the standard clock.

[0049] In order to facilitate the implementation of the method, a synchronization time window is set, and the window width of the standard clock is ΔT 0 , the window width of the clock to be synchronized is ΔT 1 In addition, let the time axis of the standard clock be t and the time axis of the clock to be synchronized be t 1 ,like Figure 2 As shown. Then when b>1, ΔT 1 <ΔT 0 ; ΔT when b<1 1 >ΔT 0 .

[0050] The size of the standard clock time window depends on the accuracy requirement to be synchronized. For example, if the accuracy requirement is at the millisecond level, it can be set to the microsecond level; if the accuracy requirement is at the microsecond level, it can be set to the nanosecond level, and so on.

[0051] It should be pointed out that based on the non-local correlation characteristics of quantum entanglement, rotating the polarization angle of a photon in the local optical path by Δθ will inevitably cause the other entangled photon in the opposite optical path to rotate -Δθ at the same time. The collapse of a photon state will inevitably lead to the simultaneous collapse of the other entangled photon state. The action moments of the two photons are constant and consistent, which is a necessary and sufficient condition for the establishment of quantum time synchronization method.

[0052] Depend on Figure 1 From the technical route, it can be seen that when the entangled photon reaches position A in the optical path of the local end, it reaches position A' in the optical path of the opposite end. Control the on and off of the optical switch so that the entangled photon at the local end is within a given time window ΔT 0 After passing through the inner part, the polarization angle Δθ is changed after being modulated by the λ / 2 wave plate, and the polarization angle of the entangled photon at the opposite end is also changed by Δθ at the same time. After polarization detection, the maximum light intensity duration ΔT of the photodetector is obtained. 1 When the clocks at both ends are synchronized, ΔT 1 =ΔT 0 .

[0053] ΔT 0 is the known time window width based on the standard clock, ΔT 1 is the known time window width based on the clock to be synchronized. When not synchronized, ΔT 0 ≠ΔT 1, because a≠0, b≠1.

[0054] The time synchronization process is to adjust a and b. ΔT can be used 0 and ΔT 1 The cut-off time point of the window is ΔT due to the non-local correlation characteristics of quantum entanglement. 0 and ΔT 1 The end time of the window is constant. The following example illustrates the synchronization process:

[0055] 1) Optical switch on time ΔT 0 +T (e.g. T = 100ns, local timing), if the duration of the maximum light intensity is ΔT 1 +90ns (peer timing), then b<1; if the duration of maximum light intensity is ΔT 1 +110ns (timed by the other end), then b>1. Adjust the unit time interval of the clock to be synchronized so that b=1, that is, the time intervals of the clocks at both ends are consistent.

[0056] 2) By Figure 1 From the technical route, we can know that the time window is a pulse signal. Sending a pulse string by an agreed mode can realize single-ended communication. Therefore, a timestamp can be sent to the other end to adjust the origin difference so that a=0, which completes the synchronization of the clocks at both ends.

[0057] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

[0058] This patent is not limited to the above-mentioned best implementation mode. Anyone can derive other forms of quantum time synchronization methods for power systems under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A method for quantum time synchronization of a power system, characterized in that: The polarization entangled photon pair is output through the all-fiber polarization entangled photon source. One of them enters the optical fiber channel and is sent to the other end. After collimation, polarization detection and photoelectric detection, a time synchronization signal is obtained. The other one enters the local optical path in spatial light mode and is collimated, adjustable delay device, optical switch, λ / 2 wave plate and then annihilates itself; The standard clock unit is used to control the on and off of the optical switch, so that the entangled photons can be turned on and off in a given time window. ∆T Passed within 0, λ / 2 After the wave plate is modulated, the polarization direction of the photon changes by an angle ∆θ Based on the non-local correlation characteristics of quantum entanglement, the polarization angles of the entangled photons at the opposite ends change at the same time. ∆θ ; The on-time of the optical switch controlled by the standard clock unit is ∆T； Set the polarization axis of the polarizer on the opposite end so that θ =0, the light intensity detected by the photoelectric detection unit is the minimum. θ =- ∆θ When the light intensity is the largest, the time window of maximum light intensity is ∆T 1. When ∆T 1= ∆T When the step difference between the clock to be synchronized and the standard clock is 0, the clocks at both ends are synchronized; when the clocks at both ends are synchronized, ∆T 1= ∆T 0; When the clocks at both ends are not synchronized, ∆T 1< ∆T 0.

2. The power system quantum time synchronization method according to claim 1, characterized in that: The adjustable delay device is used to compensate for the time delay of the optical fiber channel so that the entangled photons can reach the position A When it reaches A’ position to ensure that the optical switch and λ / 2 The wave plate works effectively; A-A' Through the non-local correlation of quantum entanglement, the position A Previous light path and position A’ The subsequent optical paths are connected together to form a complete optical path.

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