Speaker: Dr. Hsiang-Sheng Ku (古祥生博士), Alibaba DAMO Academy
Time：2021/12/3  Friday 2:00PM-3:00PM
Place：Lecture room 620, Dept. of Phys. 
Title : Fluxonium: an alternative qubit platform for high-fidelity operations
Abstract: 
Superconducting qubits provide a promising path toward building large-scale quantum computers.  The simple and robust transmon qubit has been the leading platform, achieving multiple milestones.  However, fault-tolerant quantum computing calls for qubit operations at error rates significantly lower than those exhibited in the state of the art. Consequently, alternative superconducting qubits with better error protection have attracted increasing interest.  Among them, fluxonium is a particularly promising candidate, featuring large anharmonicity and long coherence times.  In this talk, we present on engineering a fluxonium-based quantum processor that integrates high qubit-coherence, fast frequency-tunability, and individual-qubit addressability for reset, read-out, and gates.  With simple and fast gate schemes, we achieve an average single-qubit gate fidelity of 99.97% and a two-qubit gate fidelity of up to 99.72%. This performance is comparable to the highest values reported in the literature of superconducting circuits. Our work, for the first time within the realm of superconducting qubits, reveals an approach toward fault-tolerant quantum computing that is alternative and competitive to the transmon system.

Biography:
Hsiang-Sheng Ku received his B.S. in Physics in 2003 from the National Taiwan University in
Taiwan and his Ph.D. in physics in 2014 from the University of Colorado Boulder in USA. His
Ph.D. dissertation experimentally studied the generation and verification of propagating microwave entangled states utilizing Josephson parametric amplifiers. He was a postdoctoral associate at the University of Colorado and worked in the Quantum Processing Group in NIST Boulder, CO. His postdoctoral research focused on designing high-coherence superconducting quantum circuits towards building superconducting quantum simulation and computation systems. He is currently a quantum scientist in Alibaba DAMO Academy.