演讲人： Benjamin Huard [Ecole Normale Supérieure de Lyon]
时间：10:00-11:30, Oct 17, 2025 (Fri)
地点：RM S527, MMW Building
内容：
Is it possible to count the number of photons in a microwave cavity by exploiting the dispersive interaction between a superconducting qubit and the cavity? In standard protocols, this operation requires to perform a series of gates on the qubit that are conditioned on the cavity occupation, followed by readout operations on the qubit using an ancillary readout resonator. Recently, our group introduced a new, efficient way to realize this counting by multiplexing the driving tones on the qubit and continuously extracting information about the number of photons. I will show an experiment in which we apply this technique to resolve the cavity photon number in a single shot of the protocol. The cavity is a 3D superconducting resonator whose lifetime is above 200 µs. A carefully designed filter allows us to drive and measure the emitted field by the qubit at a rate that is orders of magnitude larger than the decay rate of the cavity. Our proposed multiplexing scheme is equivalent to repeatedly exciting the qubit. The heterodyne detection of the fluorescence field that the qubit emits at all frequencies reveals the photon number in the cavity and produces the corresponding quantum backaction on the cavity state. The achieved measurement rate is measured to be more than one order of magnitude higher than the decay rate of the cavity, thus allowing us to track the number of photons as a function of time.
个人简介:
Benjamin Huard graduated from the Ecole Normale Supérieure of Paris in 2003 and did his PhD studies in the Quantronics group at CEA Saclay (France) with Hugues Pothier. There, he performed experiments aiming at investigating the behavior of electrons in mesoscopic metallic and superconducting conductors. In 2006, he joined the Goldhaber-Gordon group at Stanford University (USA) as a post-doc fellow, and observed the Klein tunneling of electrons in graphene for the first time. In 2008, as a CNRS researcher, he cofounded the Quantum Electronics group at Ecole Normale Supérieure (Paris, France) with Michel Devoret. Since then, he worked on superconducting circuits in which he worked on quantum measurement and feedback, thermodynamics of quantum information, microwave quantum optics, and quantum error correction. He is now a professor at Ecole Normale Supérieure de Lyon where he moved in 2017 and leads the Quantum Circuit Group together with Audrey Bienfait. He is a scientific adviser of the Alice&Bob company since 2021, scientific adviser of CNRS Physics since 2024, deputy member of section 28 Conseil National des Universités since 2024, member of the editorial board of PRX since 2024, and scientific adviser of the Isentroniq company since 2025.
