报告题目：Waveguide quantum electrodynamics with superconducting artificial atom and spin ensembles

报  告 人：许耀铨 教授，香港城市大学

研究方向：超导量子信息实验

报告时间：2024年5月28日（星期二）上午10:00

报告地点：量子楼410报告厅

报告摘要：

In this talk, I will address recent advances in waveguide quantum electrodynamics with superconducting artificial atom and spin ensembles.

In the first set of experiments, we investigate the amplification of a microwave probe signal by a superconducting artificial atom, a transmon, positioned at the end of a semi-infinite transmission line, under a strong pump field. The end of the transmission line acts as a mirror for microwave fields. Due to the weak anharmonicity of the artificial atom, the strong pump field creates multi-photon excitations among the dressed states. Transitions between these dressed states, Rabi sidebands, give rise to either amplification or attenuation of the weak probe. We obtain a maximum power amplification of 1.402, higher than in any previous experiment with a single artificial atom. Additionally, we achieve near-quantum-limited added noise (0.157 quanta; the quantum limit is 0.143 quanta for this level of amplification, due to quantum coherence between Rabi sidebands, leading to constructive interference between emitted photons.

In the second set of experiments, we investigate microwave interference from a spin ensemble and its mirror image in a one-dimensional (1D) waveguide. Away from a mirror, the resonance frequency of the Kittel mode (KM) inside a ferrimagnetic spin ensemble has a sinusoidal frequency shift as the normalized distance increases compared to the setup without the mirror. This shift is attributed to the interaction of the KM with its own image. Meanwhile, its radiative decay rate shows a cosine squared oscillation. We also observe the critical coupling condition that enables perfect adsorption of the input photons. By placing the KM near the node of resonance field, the lifetime is more than eight times than near the antinode.

报告人简介：

许耀铨，2007年获台湾国立交通大学电物理系学士学位。2013 年在瑞典查尔姆斯理工大学微技术与纳米科学系获得博士学位。他的论文主要研究使用超导电路的微波量子光学。后移居美国加州大学圣巴巴拉分校，从事量子限幅放大器工作。许耀铨博士发表了24篇期刊，其中包括 1 篇Nature Physics （第一作者）、5 篇Physical Review Letters（3 篇第一作者、2篇通讯作者），被引用共3317次，h-index为21。