Cottet Nathanaël, Xiong Haonan, Nguyen Long B, Lin Yen-Hsiang, Manucharyan Vladimir E
Physics Department, University of Maryland, College Park, MD, 20742, United States.
Université Lyon, ENS de Lyon, Université Claude Bernard Lyon 1, CNRS, Laboratoire de Physique, F-69342, Lyon, France.
Nat Commun. 2021 Nov 4;12(1):6383. doi: 10.1038/s41467-021-26686-x.
Interfacing long-lived qubits with propagating photons is a fundamental challenge in quantum technology. Cavity and circuit quantum electrodynamics (cQED) architectures rely on an off-resonant cavity, which blocks the qubit emission and enables a quantum non-demolition (QND) dispersive readout. However, no such buffer mode is necessary for controlling a large class of three-level systems that combine a metastable qubit transition with a bright cycling transition, using the electron shelving effect. Here we demonstrate shelving of a circuit atom, fluxonium, placed inside a microwave waveguide. With no cavity modes in the setup, the qubit coherence time exceeds 50 μs, and the cycling transition's radiative lifetime is under 100 ns. By detecting a homodyne fluorescence signal from the cycling transition, we implement a QND readout of the qubit and account for readout errors using a minimal optical pumping model. Our result establishes a resource-efficient (cavityless) alternative to cQED for controlling superconducting qubits.
在量子技术中，将长寿命量子比特与传播的光子相连接是一项根本性挑战。腔量子电动力学（cQED）和电路量子电动力学架构依赖于一个失谐腔，该腔会阻挡量子比特的发射，并实现量子非破坏（QND）色散读出。然而，利用电子 shelving 效应来控制一大类将亚稳态量子比特跃迁与明亮循环跃迁相结合的三能级系统时，并不需要这样的缓冲模式。在此，我们展示了置于微波波导内的电路原子——磁通量子比特的 shelving 效应。在该装置中没有腔模的情况下，量子比特的相干时间超过50微秒，且循环跃迁的辐射寿命低于100纳秒。通过检测来自循环跃迁的零差荧光信号，我们实现了对量子比特的QND读出，并使用最小光泵浦模型来考虑读出误差。我们的结果为控制超导量子比特建立了一种资源高效（无腔）的替代cQED的方法。
