Harvard Quantum Initiative Special Seminar

Friday, February 15

3:00 PM

Jefferson 250

Di Zhu, MIT

Title: Exploiting the microwave properties of superconducting nanowires for advancing single-photon detection  

The exceptional performance of superconducting nanowire single-photon detectors (SNSPDs), including >90% detection efficiency, picosecond timing resolution, and sub-hertz dark count rate, has recently enabled many impressive demonstrations in quantum science and technology, such as the loophole-free Bell test, and record-distance quantum key distribution. However, many other quantum information processing applications, such as Boson sampling, quantum walk, and linear optical quantum computing, have more demanding requirements on photon detection, such as coincidence counting over hundreds of channels, photon number resolution, and even feed-forward operation. In this talk, we will discuss how exploiting the exotic but long-neglected microwave properties of superconducting nanowires can unlock many of these missing functionalities in SNSPDs. For example, by utilizing the slow speed of light in the nanowires, less than 2% of that in free space, we can construct delay-line-multiplexed detector arrays. From this we have demonstrated a two-terminal array architecture that is suitable for coincidence detection over large numbers of spatial modes in photonic integrated circuits, and capable of resolving photon numbers. We have further demonstrated how impedance matching of the nanowires can achieve “passive amplification” and multi-photon resolution in SNSPDs. Beyond photon detection, the nanowires may be used in diverse applications ranging from microwave coupling and switching to parametric amplification.