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Review of Scientific Instruments

Time-tagged coincidence counting unit for large-scale photonic quantum computing

Wei Li, Yi Hu, Han-Sen Zhong, Yuefei Wang, Xi‐Lin Wang, Cheng-Zhi Peng, Xiao Qiang Jiang

Published Oct 1, 2018• 9 citations
Publisher

Abstract

Real-time analysis of single-photon coincidence is critical in photonic quantum computing. The large channel number and high counting rate foreseen in such experiments pose a big challenge for the conventional time tagged method and coincidence instruments. Here we propose a real-time time-tagged coincidence method and a data filtering solution, demonstrated by a 32-channel coincidence counting unit that has been implemented successfully on a field-programmable gate array system. The unit provides high counting rates, a tunable coincidence window, and a timing resolution of 390 ps. Beyond that, it is feasible to be scaled up to 104 channels and is thus ideally suited for channel consuming applications such as boson sampling. Based on the versatility and scalability the unit has shown, we believe that it is the turn-key solution for many single-photon coincidence counting applications in photonic quantum computing.

DOI
10.1063/1.5044250

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Real-time analysis of single-photon coincidence is critical in photonic quantum computing. The large channel number and high counting rate foreseen in such experiments pose a big challenge for the conventional time tagged method and coincidence instruments. Here we propose a real-time time-tagged coincidence method and a data filtering solution, demonstrated by a 32-channel coincidence counting unit that has been implemented successfully on a field-programmable gate array system. The unit provides high counting rates, a tunable coincidence window, and a timing resolution of 390 ps. Beyond that, it is feasible to be scaled up to 104 channels and is thus ideally suited for channel consuming applications such as boson sampling. Based on the versatility and scalability the unit has shown, we believe that it is the turn-key solution for many single-photon coincidence counting applications in photonic quantum computing.
Coincidence counters play the role of gating events from the background noise in almost every quantum photonics setup. Precise multi-channel and high count-rate coincidence counting tools have become desirable due to an increase in the complexity of quantum photonics experiments. However, timing analyzers are struggling to meet these needs. We are proposing a Field Programmable Gate Array (FPGA) based coincidence counting system which provides 8 operational channels with 8.9 ps root mean square (RMS) resolution (with a bin width of 7.7 ps) and a count-rate of 320 million counts per second (MCPS) (with 40 MCPS per channel). We have successfully tested our design in different quantum photonics scenarios such as the detection of two-photon interference and pseudo-photon-number resolving detection of a coherent state of light where it has shown its capability of working beyond the saturation of detectors. Also, we have introduced a Dual Data Rate Registration TDC, which improved the linearity of the time tagging operation by using both clock edges without increasing the dead-time or using the space excessively. 1.2 LSB in max DNL error, 1.8 LSB in max INL error, 10 ps in FWHM and 3.2 ps in RMS resolution improvements were achieved.
The increasing complexity of recent photonic experiments challenges the development of efficient multichannel coincidence counting systems with high-level functionality. Here, we report a coincidence unit able to count detection events ranging from single to 16-fold coincidences with full channel-number resolution. The device operates within sub-100-ps coincidence time windows, with a maximum input frequency of 1.5 GHz and an overall jitter of less than 10 ps. The unit high-level timing performance renders it suitable for quantum photonic experiments employing low-timing-jitter single-photon detectors. Additionally, the unit can be used in complex photonic systems to drive feed-forward loops. We demonstrate the developed coincidence counting unit in photon-number-resolving detection to directly quantify the statistical properties of light, specifically coherent and thermal states, with a fidelity exceeding 0.999 up to 60 photons.
A flexible and low-cost Coincidence Counting Unit (CCU) with customizable features that are software selectable is designed and developed for the use in various experiments of quantum information and quantum metrology. A digital logic-based implementation approach using Field Programmable Gate Array is followed with specific emphasis on reducing the time for coincidence events of photons and making it easily scalable. In this paper, an 8-channel CCU with software configurable features such as coincidence window selection (in increment of 0.54 ns) and 8-fold coincidences (up to 4 sets) at a time has been implemented.
We present a fast and compact multichannel coincidence unit to count all possible single and coincidence detection events in an experiment with eight single-photon detectors at once. Using high-speed electronics and a microcontroller, this device is able to process up to 800000events∕s. The coincidence window can be tuned within a range of 4–12ns. The device can be easily scaled to any number of input channels and is thus ideally suited for efficient multiphoton quantum information processing.
We introduce a compact 64-channel detection system tailored for high-precision, time-resolved single-photon measurements in quantum photonic applications such as Boson Sampling and Hong-Ou-Mandel interferometry. The system integrates an 8×8 SPAD array (30 µm active area, 75 µm pitch) with microlenses, achieving a 76% fill-factor, <100 ps jitter, and low dark count rates. Two acquisition boards—each featuring four TACs with four channels—provide 32 timing channels, with a 2:1 multiplexing scheme enabling full array coverage. Time tags are generated via FPGA and transferred through USB 3.0 at rates up to 700 MB/s. This system will support upcoming multi-photon experiments at the Italian Space Agency (ASI).
Coincidence counting is widely used in quantum optics.It could be used in measuring the pairs of polarization entangled photons and single photon interference.In quantum experiments,coincidence counting often needs more than 3 channels.In this case,it is necessary to use FPGA(Field-Programmable Gate Array) instead of discrete logic chips.FPGA also has the advantage of low cost and small size.Coincidence counter based on FPGA could support coincidence time window from 1 ns to several hundred ns.This helps to avoid noised caused by background light.This paper introduces the principle of multi-channel coincidence counter based on FPGA and gives its performance experimentally with two single photon counting modules.