Photon number distinguishing time-to-digital conversion system

Abstract

The invention relates to a time-to-digital conversion system for photon number resolution. According to the system, the input of a signal beam splitting module is an original analog signal output by a photon number resolution detector, and the output of the signal beam splitting module is two paths of synchronous analog signals; the dual-channel time measurement module receives the two paths of synchronous analog signals and outputs arrival time signals of the two paths of digital pulse signals; and the photon number and time processing module receives the arrival time signal, synchronously outputs the photon number and the photon arrival time after data processing, codes the photon number and the photon arrival time and stores the photon number and the photon arrival time in the same storage word of the memory. The system can realize simultaneous measurement of photon number and time.

Description

A photon number-resolved time-to-digital conversion system Technical Field

[0001] This application relates to the field of communication technology, and in particular to a photon number-resolved time-to-digital conversion system. Background Technology

[0002] Optical quantum computing typically requires time measurement and coincidence counting of multiple photons to perform complex calculations. While increasing the number of single-photon detectors and back-end processing circuits can effectively improve computing power, this stacking makes the system bloated, hindering the miniaturization and practical application of optical quantum computers. Introducing end-to-end photon number resolution capability can significantly improve computing power without increasing the number of channels. This can be considered from two aspects: single-photon detectors and time-to-digital converters. Single-photon detectors with photon number resolution capability include photomultiplier tubes, arrayed superconducting nanowires, superconducting transition edge detectors, and microwave dynamic inductive detectors. Currently, in optical quantum computing prototype systems, photon number resolution based on these photon number resolution detectors is mainly achieved through post-processing, resulting in low data processing efficiency and primarily used for principle verification.

[0003] Currently, time-to-digital conversion technology possesses high-resolution and high-precision time measurement capabilities, but it lacks photon number resolution capabilities, becoming a barrier to end-to-end photon number resolution and hindering the further transformation of quantum computing towards higher speeds, miniaturization, and practical applications. Therefore, conducting research on photon number-resolution time-to-digital conversion technology and designing an integrated photon number-resolution time-to-digital conversion system has significant scientific and application value. Summary of the Invention

[0004] Therefore, it is necessary to provide a photon number-resolution time-to-digital converter system that can meet the urgent need for end-to-end photon number resolution in optical quantum computing, addressing the aforementioned technical problems.

[0005] A photon number-resolved time-to-digital conversion system, the system comprising a signal beam splitting module, a dual-channel time measurement module, and a photon number and time processing module;

[0006] The input to the signal beam splitting module is the original analog signal output from the photon number resolution detector, and the output is two synchronous analog signals. The dual-channel time measurement module receives two synchronous analog signals and outputs the arrival time signals of two digital pulse signals. The photon number and time processing module receives the arrival time signals, processes the data, and synchronously outputs the photon number and photon arrival time, and encodes and stores them in the same memory word.

[0007] The aforementioned photon number-resolved time-to-digital conversion system firstly designs a signal beam splitter module to directly receive the raw analog signal from the photon number-resolved detector. The characteristic that the signal amplitude is proportional to the photon number provides the basis for photon number resolution. Its output of two synchronous analog signals ensures consistent channel routing time, establishing a unified benchmark for subsequent dual-channel measurements and avoiding errors introduced by signal transmission differences. Furthermore, it eliminates the need for additional preprocessing circuitry, simplifying the system structure and contributing to miniaturization. Secondly, the dual-channel time measurement module employs a dual-threshold comparison design. It utilizes two synchronous analog signals to trigger different comparison voltages to form a stable time difference, indirectly converting photon number information into a time difference signal. Combined with high-precision time measurement based on the rising edge, it achieves synchronous acquisition of time information and photon number correlation information, breaking through the limitation of traditional time-to-digital conversion technology that can only measure time. Moreover, this module does not rely on an external auxiliary signal source, further reducing the system size. Finally, the photon count and time processing module directly receives two arrival time signals, quickly calculates the photon count using a time difference and photon count calibration correlation algorithm, and accurately obtains the arrival time using the averaging method, achieving synchronous output of both signals. This completely eliminates the post-processing process of traditional solutions and significantly improves data processing efficiency. Simultaneously, the two types of information are encoded and stored in the same memory word, providing a directly readable data format for subsequent coincidence counting in optical quantum computing, avoiding the additional time consumption of data correlation. Furthermore, the proportionally expanded design of each module enables multi-channel measurement without interfering with single-channel processing speed or significantly increasing system size. This solves the bloated problem caused by stacking circuits to improve computing power in traditional solutions, ultimately balancing high-speed processing and miniaturization requirements, providing core support for the practical application of optical quantum computing. Attached Figure Description

[0008] Figure 1 is a schematic diagram of a photon number-resolved time-to-digital conversion system in one embodiment; Figure 2 is a schematic diagram of a signal beam splitting module in one embodiment; Figure 3 is a schematic diagram of a dual-channel time measurement module in one embodiment; Figure 4 is a schematic diagram of a photon number and time processing module in another embodiment. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0010] In one embodiment, as shown in Figure 1, a photon number-resolved time-to-digital conversion system is provided, including a signal beam splitting module, a dual-channel time measurement module, and a photon number and time processing module; the input of the signal beam splitting module is the original analog signal output by the photon number-resolved detector, and the output is two synchronous analog signals.

[0011] As we can understand, a photon number-resolved detector is a photoelectric detection device with photon number resolution capability, including photomultiplier tubes, arrayed superconducting nanowires, superconducting transition edge detectors, and microwave dynamic inductive detectors. The amplitude of its output raw analog signal is directly proportional to the number of incident photons; that is, the more photons, the larger the signal amplitude. Two synchronous analog signals refer to signals that, after processing by the signal beam splitting module, maintain consistency in the time dimension, with no additional transmission delay differences. This ensures a unified benchmark for subsequent dual-channel measurements, laying the foundation for accurate time difference calculation. The core function of this module is to preprocess the raw analog signal to adapt it to the input requirements of the subsequent dual-channel time measurement module, while also being compatible with photon number-resolved detectors with different response characteristics.

[0012] The dual-channel time measurement module receives two synchronous analog signals and outputs two digital pulse signals with arrival time signals.

[0013] The dual-channel time measurement module achieves the correlation and capture of photon count and time information through a dual-threshold design. "Dual-channel" refers to two independent signal processing links, each processing a synchronous analog signal. The digital pulse signal is a rectangular wave signal obtained by threshold conversion of the analog signal through a voltage comparator circuit; its rising edge corresponds to the moment the analog signal reaches the comparison voltage. The arrival time signal is the trigger time of the rising edge of the two digital pulse signals (T). H T L This module calculates the time difference, which is invariably related to the number of incident photons and serves as the core basis for subsequent photon count calculations. Through this module, the conversion from analog to digital time signals is achieved while preserving the amplitude information related to the photon count.

[0014] The photon count and time processing module receives the arrival time signal, processes the data, and synchronously outputs the photon count and photon arrival time, and encodes and stores the two in the same memory word.

[0015] The photon number and time processing module processes data based on two time signals and converts them into a unified data format for particle number and time, storing it in the same memory word. The arrival time signal is T. H T LThis module converts time information into photon counts and precise arrival times using a specific algorithm. Synchronous output means that the calculation of photon counts and arrival times is completed in parallel, eliminating the need for staged processing and significantly improving data processing efficiency. This solves the inefficiency problem caused by the reliance on post-processing in traditional solutions. The same storage word means that the photon count and time information corresponding to the same photon pulse are stored in the same address unit of the memory, using a unified data format. This facilitates direct reading of coincidence counts in subsequent quantum computing without the need for additional data association operations, further improving the overall system computational efficiency. This module realizes data calculation, fusion, and efficient storage, and is a core component of the system's integrated design.

[0016] The aforementioned photon number-resolved time-to-digital conversion system enables simultaneous measurement of photon number and time. Its processing speed is far greater than that of existing technical solutions. Furthermore, the signal beam splitting module, dual-channel time measurement module, and photon number and time processing module can be expanded as needed to achieve multi-channel input measurement. Moreover, the increase in system size during expansion is less than that of existing solutions. It not only solves the problem of simultaneously measuring photon arrival time and number but also takes into account high speed and miniaturization, providing a practical solution for photon number-resolved time measurement in optical quantum computing towards high speed and miniaturization.

[0017] In one embodiment, the signal beam splitting module includes an amplification circuit and a beam splitting circuit. The amplification circuit accurately amplifies the original analog signal and transmits it to the beam splitting circuit. The beam splitting circuit splits the amplified analog signal into two synchronous analog signals, and the two output channels of the beam splitting circuit have the same routing time.

[0018] The core function of the amplifier circuit is to adapt to the amplitude differences in the output signals of detectors with different photon number resolutions, ensuring that the minimum signal of the single-photon response can be accurately identified by the subsequent voltage comparison circuit, while preventing the signal of the maximum photon number response from exceeding the output range of the amplifier circuit, thus avoiding distortion. The beam splitter circuit adopts a symmetrical design, and by optimizing the wiring layout, it ensures that the routing time of the two output channels (Sin1, Sin2) is exactly the same, eliminating the additional time difference introduced by the difference in transmission path length, ensuring the synchronization of the two signals, and preventing this difference from being misinterpreted as a time difference related to the photon number, thus affecting the measurement accuracy. Precise amplification achieves compatibility with signals from different detectors, and synchronous beam splitting ensures the consistency of the measurement reference, providing a prerequisite for the accuracy of subsequent dual-channel time measurements. At the same time, the modular integrated design is conducive to system miniaturization.

[0019] In one embodiment, the amplification factor of the amplifier circuit is determined as follows: first, the minimum amplitude V of the single-photon response of the photon number-resolved detector is calibrated. smin Maximum number of photons to be resolved, N smax and the corresponding maximum amplitude V smax Combined with the maximum output signal amplitude V of the amplifier circuitmax Define the range of values ​​for the amplification factor A, and ensure that the amplitude of the detector output signal is proportional to the number of photons.

[0020] Specifically, considering the differences in response characteristics of different types of photon number-resolved detectors, and the different output signal amplitudes of the same photon number-resolved detector for different numbers of photons, the signal beam splitting module needs to process the signal output to the dual-channel time measurement module. The designed signal beam splitting module is shown in Figure 2. The input and output of the module are both analog signals.

[0021] Due to the original input signal (S) in The amplitude varies with the number of photons the photon number-resolved detector responds to. The first step is to determine the minimum amplitude V of the photon number-resolved detector in single-photon response. smin The maximum number of photons that can be resolved, N smax and the corresponding maximum amplitude V smax Since the amplitude is proportional to the number of photons, if the amplitude of the N-photon response is V... sN Then the following condition is met: (1) At this time, if the maximum output signal amplitude of the amplifier circuit is V max To achieve better measurement results, the magnification A can be selected from the following range: (2) The amplified signal is to be output to the subsequent module simultaneously after passing through the beam splitter circuit. Therefore, it is necessary to ensure that the two output channels in the beam splitter circuit have the same routing time.

[0022] Through precise calibration and amplification optimization, the system effectively identifies signals with different photon numbers, is compatible with detectors with different response characteristics, and improves the system's versatility and measurement accuracy.

[0023] In one embodiment, the dual-channel time measurement module includes a voltage comparison circuit and a time measurement circuit, wherein the voltage comparison circuit uses two different comparison voltages V. H V L Threshold conversion is performed on the two synchronous analog signals to output two digital pulse signals, and the trace times of the two comparison channels of the voltage comparator circuit are exactly the same; the time measurement circuit measures the arrival time T of the two signals based on the rising edge of the two digital pulse signals. H T L It is output as an arrival time signal to the photon count and time processing module.

[0024] Specifically, the dual-channel time measurement module, as shown in Figure 3, includes a voltage comparison circuit and a time measurement circuit. The two signals (Sin1, Sin2) after passing through the signal beam splitter first enter the voltage comparison circuit. The comparison voltages VH and VL of the two signals differ. Assuming VH > VL, to achieve better measurement results, the comparison voltages VH and VL can be selected within the following ranges: (3) (4) The signals after passing through the voltage comparison circuit must be output to the time measurement circuit simultaneously. Therefore, it is necessary to ensure that the two comparison circuit channels in the voltage comparison circuit have the same trace time. At this time, due to the difference in comparison voltage, there will be a time difference ΔT between the rising edges of the two rectangular waves input to the time measurement circuit. The time measurement circuit measures the arrival time T of the two channel signals based on the rising edges. H T L If V H >V L Then T H T L satisfy: (5) The voltage comparison circuit contains two independent comparison units, each using a different comparison voltage V. H (High threshold) and V L (Low threshold), and V H >V L Since the amplitude of the detector output signal is proportional to the number of photons, the amplified signal amplitude A of the N-photon response... V Sn It will increase as N increases, therefore it will reach V first. L The low threshold comparison unit is triggered, and then V is reached. H The high-threshold comparator unit is triggered, thereby establishing a stable time difference ΔT between the rising edges of the two digital pulse signals. By optimizing the circuit layout, the trace times of the two comparison channels are ensured to be exactly the same, avoiding transmission delay interference with the accuracy of ΔT. The time measurement circuit employs high-resolution time-to-digital conversion (TDC) technology, accurately capturing the trigger time T based on the rising edge of the digital pulse signal. H T L The time measurement accuracy reaches a high resolution level, meeting the high-precision time measurement requirements of optical quantum computing. A dual-threshold design establishes a correlation between time difference and photon count; a channel synchronization design ensures the accuracy of time difference measurement; and a high-precision time measurement circuit ensures the accuracy of arrival time measurement, providing reliable data support for subsequent precise calculations of photon count and time.

[0025] In one embodiment, the two different comparison voltages satisfy V H >V L And V H V LThe value range is determined in conjunction with the signal amplitude characteristics of the photon number-resolution detector, ensuring a stable time difference between the rising edges of the two converted digital pulse signals. .

[0026] Specifically, V L The value of V must be lower than the minimum amplitude of the amplified single-photon response, i.e., V L V smin This ensures that the single-photon signal can stably trigger the low-threshold comparison unit; V H The value of A must be between the amplitude of the single-photon response and the amplified amplitude of the maximum photon number response, i.e. V smin <V H V smax This ensures that the time difference ΔT between the triggering dual thresholds for signals with different photon counts is significantly different, and that this difference is stable and distinguishable. This is achieved by reasonably defining V... H V L The range ensures that different photon numbers correspond to different stable ΔT, providing a prerequisite for accurate resolution of photon numbers, avoiding misjudgment of photon numbers due to improper threshold settings, and improving the measurement reliability of the system.

[0027] In one embodiment, the photon count and time processing module is shown in Figure 4. The photon count and time processing module includes a photon count and time calculation and processing unit and a storage unit; the photon count and time calculation and processing unit receives the arrival time signal T. H T L The photon count is calculated based on the time difference combined with a photon number resolution algorithm, and the photon arrival time is calculated based on the average value method; the storage unit receives the encoded photon count. The arrival time T of the photon is stored in the same storage word.

[0028] Comparison voltage V H V L If the amplitude of the N1 photon response is V sn2 The rise time is τ n1 The time difference is ΔT n1 The amplitude of the N2 photon response is V sn2 The rise time is τ n2 The time difference is ΔT n2 Then the time difference ΔT n1 and ΔT n2 satisfy: (6) Combining formula (1), the relationship between time difference and quantity can be further determined as follows: ​​(7) Therefore, the time difference and quantity are calibrated by combining the rise time and time difference measurements of different number responses at different temperatures. If the rise time of the photon number-resolved detector remains basically unchanged under constant temperature, and the time difference of 1 photon response is ΔT1, then the relationship between the time difference ΔT and the quantity N can be further simplified as follows: (8) That is, only the time difference and quantity need to be calibrated by measuring the response time difference of 1 photon. In actual measurement, due to noise, the algorithm for determining the number of photons as N is as follows: (9) The photon arrival time T can be calculated as the average of the times measured under two threshold conditions: (10) After the processing unit calculates the above photon number N and time T, it encodes them into binary code. The memory stores the time and photon number information of the same pulse signal in the same storage word for subsequent data processing and analysis.

[0029] Specifically, the computing unit is the core computational component of the module, employing a hardware-based logic design to ensure parallel processing capabilities and high-speed computational efficiency. Regarding photon count calculation, a standard time difference database corresponding to different photon counts is first established through experimental calibration, and then calculated during actual measurements. The system determines the number of incident photons by matching a standard time difference interval using a photon number resolution algorithm. For time calculation, an averaging method is employed to offset random errors caused by single-threshold triggering, improving time measurement accuracy. The storage unit utilizes a high-speed memory, supporting the storage of multiple data types within the same memory word. After receiving binary-coded data output from the computational processing unit, it stores it in a unified format, ensuring a one-to-one correspondence between the photon number and time information for the same photon pulse. The hardware-based computational processing unit enables synchronous high-speed calculation of photon number and time. The averaging method improves time measurement accuracy, and the single-word storage design simplifies subsequent data reading and correlation operations, comprehensively enhancing the system's data processing efficiency and usability.

[0030] In one embodiment, the photon number is calculated based on the time difference combined with a photon number resolution algorithm.

[0031] in, Indicates time difference, This represents the standard time difference corresponding to the (n+1)th photon count. This represents the standard time difference corresponding to the calibrated nth photon number. The index indicating the number of photons. Indicates the maximum number of photons. This represents the standard time difference corresponding to the maximum photon number. This represents the standard time difference corresponding to the maximum calibrated number of photons minus 1.

[0032] In one embodiment, the photon arrival time is calculated based on the average value method. .

[0033] Specifically, T H It is the high threshold comparison voltage V H The corresponding trigger time, T L It is the low threshold comparison voltage V L The corresponding trigger time, since the routing time of the two comparison channels is exactly the same, T H With T L The difference is determined solely by the signal amplitude characteristics, and its average value can effectively offset random noise interference that may exist during single-threshold triggering, while also being closer to the actual time when photons arrive at the detector. For example, if noise causes T... H Slight delay, T L A slight advance in time measurement can be offset by averaging the two methods, thus improving the stability and accuracy of the time measurement. The algorithm is simple and efficient, requiring no complex calculations and having low hardware implementation costs. It also effectively improves time measurement accuracy, meeting the high-precision time measurement requirements of quantum computing.

[0034] In one embodiment, the computing unit converts the calculated photon count and photon arrival time into binary code, and the storage unit receives the binary code using a unified data format, thereby achieving joint storage of the photon count and time information of the same photon pulse signal, which can be directly read by the coincidence count in subsequent optical quantum computing.

[0035] Specifically, the computing unit incorporates an encoding module that converts the photon count and arrival time into fixed-length binary codes. For example, the photon count uses 8-bit binary encoding, and the time uses 32-bit binary encoding, combined into a unified 40-bit data format. The storage unit stores this unified format data sequentially by address, with each address corresponding to the complete information of a photon pulse. During subsequent coincidence counting in quantum computing, data can be directly read by address without additional parsing or correlation operations, significantly reducing data processing latency. The binary encoding adapts to the hardware storage and retrieval logic, the unified data format improves storage and retrieval efficiency, and the combined storage design simplifies the subsequent coincidence counting process, further enhancing the overall computational efficiency of the system and supporting the high-speed operation of quantum computing.

[0036] In one embodiment, the synchronous measurement of multiple photon pulse signals is achieved by proportionally expanding the input channel of the signal beam splitting module, the comparison circuit channel of the dual-channel time measurement module, and the computation and storage channel of the photon count and time processing module, while maintaining independent signal processing links between each expanded channel without mutual interference. The processing speed of a single signal after expansion is consistent with that of a single-channel system.

[0037] Specifically, in multi-channel expansion, the signal beam splitting module increases the number of input channels, with each input channel corresponding to one original analog signal from a photon number-resolved detector, and each input channel is equipped with an independent amplification circuit and beam splitting circuit; the dual-channel time measurement module increases the number of comparison circuit channels proportionally to the number of input channels (each input corresponds to a pair of V... H V L The system includes a comparison channel and a time measurement circuit unit; the photon count and time processing module adds computation and storage channels, with each channel corresponding to the calculation and storage of photon count and time for one signal. The signal processing links for each extended channel are completely independent, and interference between channels is avoided through parallel allocation of hardware resources, ensuring that the processing flow for each signal is consistent with the single-channel system, and the processing speed is not affected by the number of extended channels. This achieves synchronous parallel measurement of multiple photon signals, eliminating the need for stacking independent systems to achieve multi-channel measurement. The increase in system size is far less than traditional solutions, balancing multi-channel measurement requirements with miniaturized design, further expanding the system's application scenarios, and meeting the needs of optical quantum computing for multi-channel photon processing.

[0038] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0039] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A photon number-resolved time-to-digital conversion system, characterized in that, It includes a signal beam splitting module, a dual-channel time measurement module, and a photon count and time processing module. The input of the signal beam splitting module is the raw analog signal output by the photon number resolution detector, and the output is two synchronous analog signals. The dual-channel time measurement module receives the two synchronous analog signals and outputs the arrival time signals of two digital pulse signals. The photon count and time processing module receives the arrival time signals, processes the data, and synchronously outputs the photon count and photon arrival time, and encodes and stores them in the same memory word.

2. The system according to claim 1, characterized in that, The signal beam splitting module includes an amplification circuit and a beam splitting circuit. The amplification circuit accurately amplifies the original analog signal and then transmits it to the beam splitting circuit. The beam splitting circuit splits the amplified analog signal into two synchronous analog signals, and the two output channels of the beam splitting circuit have the same routing time.

3. The system according to claim 2, characterized in that, The amplification factor of the amplifier circuit is determined as follows: first, the minimum amplitude V of the single-photon response of the photon number-resolution detector is calibrated. smin Maximum number of photons to be resolved, N smax and the corresponding maximum amplitude V smax Combined with the maximum output signal amplitude V of the amplifier circuit max Define the range of values ​​for the amplification factor A, and ensure that the amplitude of the detector output signal is proportional to the number of photons.

4. The system according to claim 1, characterized in that, The dual-channel time measurement module includes a voltage comparison circuit and a time measurement circuit. The voltage comparison circuit uses two different comparison voltages V. H V L The two synchronous analog signals are threshold converted to output two digital pulse signals, and the trace times of the two comparison channels of the voltage comparison circuit are exactly the same; the time measurement circuit measures the arrival time T of the two signals based on the rising edge of the two digital pulse signals. H T L It is output as an arrival time signal to the photon count and time processing module.

5. The system according to claim 4, characterized in that, The two different comparison voltages satisfy V H >V L And V H V L The value range is determined in conjunction with the signal amplitude characteristics of the photon number-resolution detector, ensuring a stable time difference between the rising edges of the two converted digital pulse signals. 。 6. The system according to claim 1, characterized in that, The photon count and time processing module includes a photon count and time calculation and processing unit and a storage unit; the photon count and time calculation and processing unit receives the arrival time signal T. H T L The photon count is calculated based on the time difference combined with a photon number resolution algorithm, and the photon arrival time is calculated based on the average value method; the storage unit receives the encoded photon count. The arrival time T of the photon is stored in the same storage word.

7. The system according to claim 6, characterized in that, The photon number calculated based on the time difference combined with the photon number resolution algorithm is: in, Indicates time difference, This represents the standard time difference corresponding to the (n+1)th photon count. This represents the standard time difference corresponding to the calibrated nth photon number. The index indicating the number of photons. Indicates the maximum number of photons. This represents the standard time difference corresponding to the maximum photon number. This represents the standard time difference corresponding to the maximum calibrated number of photons minus 1.

8. The system according to claim 6, characterized in that, The photon arrival time was calculated based on the averaging method. 。 9. The system according to claim 6, characterized in that, The computational processing unit converts the calculated photon count and photon arrival time into binary code. The storage unit receives the binary code using a unified data format, realizing the joint storage of photon count and time information of the same photon pulse signal, which can be directly read for subsequent coincidence counts in optical quantum computing.

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