Photon-number resolution is a crucial aspect of quantum information technology, and it plays a vital role in various quantum systems such as quantum computation, quantum communication, and quantum metrology. Superconducting nanostrip single-photon detectors (SNSPDs) are considered the leading technology for single-photon detection due to their near-perfect efficiency and high-speed performance. However, these detectors have faced challenges in achieving a balance between fidelity and dynamic range.
Researchers from the Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences, have made significant progress in enhancing the photon-number-resolving capability of SNSPDs. By increasing the strip width or total inductance of the SNSPD, they were able to overcome bandwidth limitations and timing jitter in readout electronics. This led to stretched rising edges and improved signal-to-noise ratio in the response pulses, resulting in enhanced readout fidelity.
The researchers widened the superconducting strip of the SNSPD to a micrometer scale, leading to the first observation of true-photon-number resolution up to 10 using the superconducting microstrip single-photon detector (SMSPD). Surprisingly, they achieved these results without the use of cryogenic amplifiers, further simplifying the readout setup. The readout fidelity reached an impressive 98 percent for 4-photon events and 90 percent for 6-photon events, showcasing the advancements made in resolving the number of incident photons.
In addition to improving readout fidelity, the researchers also proposed a dual-channel timing setup to enable real-time photon-number readout. This innovative approach significantly reduced data acquisition requirements by three orders of magnitude, making the readout process more efficient and practical. The simplified readout setup allows for easier implementation in various quantum information technology applications.
The utility of the enhanced SNSPD system in quantum information technology was demonstrated through the creation of a quantum random-number generator based on sampling the parity of a coherent state. This technology ensures unbiasedness, robustness against experimental imperfections and environmental noise, as well as resistance to eavesdropping. These features make the system highly reliable and secure, making it suitable for a wide range of applications.
The research conducted by the team at SIMIT represents a significant advancement in the field of photon-number-resolving detectors. With further improvement in the detection efficiency of SMSPDs, this technology has the potential to become readily accessible for various optical quantum information applications. The high-fidelity and large-dynamic-range photon-number resolution offered by SNSPDs or SMSPDs opens up new possibilities in the realm of quantum information technology.
The advancements made in enhancing the performance of SNSPDs and the introduction of the SMSPD have greatly improved the photon-number resolution capabilities in quantum systems. The research conducted by the team at SIMIT has demonstrated the potential of SNSPDs or SMSPDs in achieving high-fidelity and large-dynamic-range photon-number resolution. These breakthroughs pave the way for the development of more efficient and practical quantum information technology applications.
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