A method and system for inter-mobile platform compliance count measurement

Abstract

This invention discloses a method and system for measuring coincidence counts between mobile platforms. The method includes directly connecting the signal light output from an entangled source to a local single-photon detector to generate a local trigger signal; generating an optical pulse in real time that is strictly synchronized with the timing of the input trigger signal according to the timing sequence of the trigger signal; combining this optical pulse with the idler light generated by the entangled source using a wavelength division multiplexer; receiving the combined optical signal at a remote mobile node, accurately separating the idler light from the pulse light using a de-wavelength division multiplexer, and recording the coincidence count (CC) using a high-speed time coincidence measurement device; the system includes an entangled source node and a remote mobile node. This invention eliminates the need for additional time synchronization steps, completely avoids the impact of time delay changes caused by platform movement, is compatible with the networking requirements of different numbers of mobile platforms, and achieves high-precision real-time coincidence count measurement.

Description

Technical Field

[0001] This invention relates to the field of free-space laser communication, and more particularly to a coincidence count measurement method and system for mobile platforms that are far apart, based on a pulsed light module. Background Technology

[0002] Free-space quantum information processing (FIP) is a technology that utilizes the principles of quantum mechanics (superposition and entanglement) to transmit quantum information in free space, enabling quantum key distribution, quantum teleportation, distributed quantum computing, and other quantum information tasks. Based on mobile platforms (drones, unmanned vehicles, etc.), FIP technology features plug-and-play functionality and flexible deployment, overcoming coverage blind spots in traditional fiber optic networks and achieving a secure information transmission system.

[0003] Entanglement-based quantum information tasks require coincidence counting measurements of entangled photons to ensure the quantum correlation characteristics of the measurement results and achieve precise correlation of data between the transmitting and receiving ends. In existing technologies, time synchronization techniques are typically used to achieve coincidence counting measurements between mobile non-local nodes. However, time synchronization not only needs to ensure a common time reference for different nodes but also needs to compensate for the time delay caused by changes in optical path length due to platform movement. Current time synchronization technologies include GPS time synchronization, atomic clock time synchronization, optical synchronization, and quantum time synchronization. GPS time synchronization and atomic clock time synchronization can ensure a common time reference for different nodes, but they cannot avoid the impact of optical path length changes. Optical synchronization and quantum time synchronization can avoid the problem of optical path length changes, but require that the loss and jitter of the free-space optical link not be too large, and require high-precision initial alignment steps.

[0004] However, after using these time synchronization methods to achieve time synchronization, it is necessary to transmit digital timestamp signals to realize coincidence counting measurements. Such solutions not only require complex hardware support and processing algorithms, but also have large processing delays. Traditional coincidence measurement methods generally rely on complex time synchronization mechanisms to ensure the consistency of measurement timing of each node by transmitting synchronization signals. However, in mobile platform scenarios, the high-speed relative motion between platforms, complex electromagnetic interference, and dynamic changes in free space transmission links can cause random fluctuations in the transmission delay of synchronization signals, which seriously affects the accuracy of time synchronization. At the same time, the synchronization signal transmission process not only increases the system complexity, but also introduces additional delays, making it difficult to meet the requirements of real-time coincidence counting. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a coincidence counting measurement method and system based on a pulsed light module for mobile platforms that are far apart; to avoid the impact of time delay changes caused by platform movement, to be compatible with the networking requirements of different numbers of mobile platforms, and to achieve high-precision real-time coincidence counting measurement.

[0006] Technical solution: The coincidence counting measurement method between mobile platforms according to the present invention includes the following steps:

[0007] (1) The signal light output from the entangled source is directly connected to the local single-photon detector to convert the single photon signal into an electrical signal that can be recognized by subsequent modules, thereby generating a local trigger signal;

[0008] (2) Based on the timing of the input trigger signal, an optical pulse that is strictly synchronized with the timing of the trigger signal is generated in real time. When the pulse optical module receives the trigger signal output in step (1), an optical pulse is generated immediately. The optical pulse is then combined with the idler light generated by the entanglement source through a wavelength division multiplexer.

[0009] (3) After receiving the beam-combined light signal, the remote mobile node accurately separates the idler light and the pulse light through the dewavelength division multiplexer, and records the coincidence count through the high-speed time coincidence measurement device;

[0010] (4) Extend the above method to the measurement scenarios of multiple mobile platforms.

[0011] Furthermore, step (1) uses an entangled source based on spontaneous parametric downconversion as the core light source. The entangled source stably outputs pairs of signal light and idler light, and the two beams of light have strict quantum correlation.

[0012] Furthermore, in step (1), the single-photon detector is an avalanche single-photon detector. When the single-photon detector captures a signal photon, it generates a standard TTL pulse signal, which is directly connected to the trigger terminal of the pulse light module.

[0013] Furthermore, the pulse light module in step (2) adopts a laser diode driving module.

[0014] Further, in step (2), the optical pulse (amplified by an optical fiber amplifier as needed) is combined with the idler light generated by the entanglement source through a wavelength division multiplexer, and the combined optical signal is transmitted to the remote mobile node through a preset free space optical transmission link.

[0015] Furthermore, in step (3), the idler light is connected to the remote single-photon detector; the pulsed light is connected to the photodetector to convert the optical pulse signal into an electrical pulse signal.

[0016] Furthermore, in step (3), the high-speed time coincidence measurement device has an adjustable coincidence time window. When two electrical signals arrive simultaneously within the set coincidence window, it is determined to be a valid coincidence event, and the coincidence count is recorded.

[0017] Further, in step (3), the idler frequency optical detection electrical signal output by the remote single-photon detector and the electrical pulse signal output by the pulse optical detector are simultaneously connected to the high-speed time coincidence measurement device.

[0018] Furthermore, in step (4), any node is used as the entanglement source and the pulsed light module deployment node. After the signal light generated by the core node triggers the pulsed light module to generate light pulses, the light pulses are combined with the idler light and the combined light signal is distributed to multiple remote mobile nodes. At the same time, any remote node can also be used as the entanglement source and the pulsed light module deployment node.

[0019] The coincidence counting measurement system between mobile platforms described in this invention includes an entangled source node and remote mobile nodes. The entangled source node includes an entangled source, an avalanche single-photon detector, and a pulsed light module. The remote mobile node includes an avalanche single-photon detector, a high-speed time coincidence counting device, and a photon detector. The signal light output from the entangled source triggers the pulsed light module to generate an optical pulse through the avalanche single-photon detector. The optical pulse is then combined with idler light and distributed to multiple remote mobile nodes. The remote mobile nodes detect the idler light's electrical signal and the electrical pulse signal, and simultaneously connect them to the high-speed time coincidence counting device.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0021] (1) This invention does not require an additional time synchronization step, can completely avoid the impact of time delay changes caused by platform movement, is compatible with the networking requirements of different numbers of mobile platforms, and achieves high-precision real-time coincidence counting measurement.

[0022] (2) This invention does not require a digital signal transmission process, but only transmits analog signals; it does not require complex time synchronization, and realizes real-time coincidence counting; since the idler light and pulse light are transmitted from the same link, there is no time delay difference caused by node movement, and it is suitable for high-speed relative movement between nodes to realize real-time coincidence measurement. Attached Figure Description

[0023] Figure 1 Flowchart of the coincidence counting measurement method between mobile platforms;

[0024] Figure 2 A diagram illustrating measurement scenarios across multiple mobile platforms. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, the coincidence counting measurement method between mobile platforms according to the present invention includes the following steps:

[0027] Step 1: Local trigger signal generation

[0028] First, a local measurement front-end is built, using an entangled source based on spontaneous parametric downconversion (SPDC) as the core light source. This entangled source can stably output paired signal and idler beams, and the two beams possess strict quantum correlations (such as photon arrival time correlation and polarization correlation), providing a physical basis for subsequent coincidence measurements. The signal beam output from the entangled source is directly connected to a local single-photon detector. This detector uses a low dark count, high quantum efficiency avalanche single-photon detector (SPAD), which can convert a single photon signal into an electrical signal that can be recognized by subsequent modules. When the single-photon detector captures a photon of the signal beam, it immediately generates a standard TTL pulse signal. This TTL pulse signal accurately characterizes the arrival time of the signal beam photon and is directly connected to the trigger terminal of the pulse beam module as the trigger reference for pulse beam generation. The generation of the TTL pulse signal is completed synchronously with the signal beam detection process, requiring no timing calibration processing, thus simplifying the system timing control logic from the source.

[0029] Step 2: Pulse generation and beam combining

[0030] The pulsed light module uses a laser diode driver module, whose core feature is the ability to generate optical pulses in real time that are strictly synchronized with the timing of the input trigger signal. When the pulsed light module receives the TTL trigger signal output from step 1, it immediately generates an optical pulse. The output optical pulse must meet the requirements of pulse width matching the TTL trigger signal and stable optical power. The optical pulse (amplified using an fiber amplifier as needed) is then combined with the idler light generated by the entanglement source using a wavelength division multiplexer. During the combining process, it is necessary to ensure that the transmission directions of the two beams are consistent and that the beam overlap is high to avoid increased transmission loss due to beam offset. The combined optical signal is then transmitted to the remote mobile node through a preset free-space optical transmission link. The core design advantage here is that the optical pulse and the idler light share the same transmission link. Regardless of any subsequent relative movement between the local and remote nodes, the transmission path length of the two beams remains consistent, fundamentally eliminating the problem of time delay fluctuations.

[0031] Step 3: Remote detection and coincidence counting implementation

[0032] After receiving the combined optical signal, the remote mobile node first precisely separates the idler light and pulsed light using a demultiplexer. The idler light is connected to a remote single-photon detector (of the same model as the local single-photon detector to ensure consistent detection characteristics) to capture the idler light photons output from the entangled source and output the corresponding electrical detection signal. The pulsed light is connected to a photodetector (PD) to convert the optical pulse signal into an electrical pulse signal. Subsequently, the idler light detection electrical signal output from the remote single-photon detector and the electrical pulse signal output from the pulsed light detector are simultaneously connected to a high-speed time coincidence measurement device. This coincidence measurement device has a built-in adjustable coincidence time window. When both electrical signals arrive simultaneously within the set coincidence window, it is considered a valid coincidence event, and the coincidence count is recorded. The entire process does not require timing calibration of the two signals; high-precision coincidence counting can be achieved by leveraging the transmission synchronization characteristics of the optical pulse and idler light.

[0033] Step 4: Multi-node expansion implementation

[0034] The coincidence counting measurement method between mobile platforms described in this invention can be easily extended to coincidence measurement scenarios involving multiple mobile platforms, such as... Figure 2 As shown. The specific expansion method is as follows: any node is used as an entanglement source and a pulsed optical module deployment node. The signal light generated by the core node triggers the pulsed optical module to generate an optical pulse, which is then combined with the idler light and the combined optical signal is distributed to multiple remote mobile nodes. Simultaneously, any remote node can also serve as an entanglement source and a pulsed optical module deployment node. Each receiving node adopts the beam splitting and detection scheme of step 3, feeding back its respective detection signal to the time coincidence measurement device, enabling joint coincidence counting among multiple nodes. During the expansion process, no additional time synchronization equipment is required; only the optical splitter, detector, and coincidence measurement channel need to be expanded according to the number of nodes, resulting in strong system scalability.

[0035] The coincidence counting measurement method between mobile platforms described in this invention requires no digital signal transmission process, only analog signals; it eliminates the need for complex time synchronization, achieving real-time coincidence counting; and since idler light and pulsed light are transmitted from the same link, there is no time delay difference caused by node movement. This invention is a method for achieving real-time coincidence measurement applicable to high-speed relative movement between nodes.

[0036] The coincidence counting measurement system between mobile platforms described in this invention includes an entangled source node and remote mobile nodes. The entangled source node includes an entangled source, an avalanche single-photon detector, and a pulsed light module. The remote mobile node includes an avalanche single-photon detector, a high-speed time coincidence counting device, and a photon detector. The signal light output from the entangled source triggers the pulsed light module to generate an optical pulse through the avalanche single-photon detector. The optical pulse is then combined with idler light and distributed to multiple remote mobile nodes. The remote mobile nodes detect the idler light's electrical signal and the electrical pulse signal, and simultaneously connect them to the high-speed time coincidence counting device.

[0037] This invention can be widely applied to various fields that require collaborative measurement using long-distance mobile platforms:

[0038] In the field of mobile quantum communication: it is used for measuring entangled photon coincidence between air-to-ground and air-to-air mobile terminals, verifying the effectiveness of entanglement distribution, and ensuring the security of quantum key distribution.

[0039] In the field of distributed mobile sensing: in scenarios such as earthquake monitoring and environmental monitoring, the sensitivity and positioning accuracy of weak signals can be improved by combining measurements from multiple mobile sensing platforms.

Claims

1. A method for inter-mobile platform compliance count measurement, the method comprising: Includes the following steps: (1) The signal light output from the entanglement source is directly connected to the local single-photon detector SPAD to convert the single photon signal into an electrical signal that can be recognized by subsequent modules, thereby generating a local trigger signal; (2) Based on the timing of the input trigger signal, an optical pulse that is strictly synchronized with the timing of the trigger signal is generated in real time. When the pulse optical module receives the trigger signal output in step (1), an optical pulse is generated immediately. The optical pulse is then combined with the idler light generated by the entanglement source through a wavelength division multiplexer. (3) After receiving the beam-combined light signal, the remote mobile node accurately separates the idler light and the pulse light through the dewavelength division multiplexer, and detects them with a single-photon detector SPAD and a photodetector PD respectively, and records the coincidence count through a high-speed time coincidence measurement device. (4) Extend the above method to the measurement scenarios of multiple mobile platforms.

2. The method of claim 1, wherein, Step (1) uses an entangled source based on spontaneous parametric downconversion as the core light source. The entangled source stably outputs a pair of signal light and idler light, and the two beams of light have strict quantum correlation.

3. The method of claim 1, wherein, In step (1), the single-photon detector is an avalanche single-photon detector. When the single-photon detector captures a signal photon, it generates a standard TTL pulse signal, which is directly connected to the trigger terminal of the pulse light module.

4. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, The pulsed light module in step (2) uses a laser diode driving module.

5. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, In step (2), the optical pulse is amplified by an optical fiber amplifier as needed, and then the optical pulse is combined with the idler light generated by the entanglement source through a wavelength division multiplexer. The combined optical signal is then transmitted to the remote mobile node through a preset free space optical transmission link.

6. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, In step (3), the idle frequency light is connected to the remote single-photon detector; the pulsed light is connected to the photodetector to convert the optical pulse signal into an electrical pulse signal.

7. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, In step (3), the high-speed time coincidence measurement device has an adjustable coincidence time window. When two electrical signals arrive simultaneously within the set coincidence window, it is determined to be a valid coincidence event, and the coincidence count is recorded.

8. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, In step (3), the idler frequency optical detection electrical signal output by the remote single-photon detector and the electrical pulse signal output by the pulse optical detector are simultaneously connected to the high-speed time coincidence measurement device.

9. The coincidence counting measurement method between mobile platforms according to claim 1, characterized in that, In step (4), any node is used as the entanglement source and the pulsed light module deployment node. After the signal light generated by the core node triggers the pulsed light module to generate light pulses, the light pulses are combined with the idler light and the combined light signal is distributed to multiple remote mobile nodes. At the same time, any remote node can also be used as the entanglement source and the pulsed light module deployment node.

10. A coincidence counting measurement system between mobile platforms, characterized in that, It includes entangled source nodes and remote mobile nodes; the entangled source node includes an entangled source, an avalanche single-photon detector, and a pulsed light module; the remote mobile node includes an avalanche single-photon detector, a high-speed time coincidence counting device, and a photon detector; the signal light output from the entangled source triggers the pulsed light module to generate an optical pulse through the avalanche single-photon detector, and the optical pulse is combined with the idler light and distributed to multiple remote mobile nodes; the remote mobile nodes detect the electrical signal and electrical pulse signal of the idler light and simultaneously connect them to the high-speed time coincidence counting device.

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