报告人：王国庆 博士 （麻省理工学院）

时 间：2023年8月30日星期三 10:00 - 11:00

地 点：腾讯会议，会议号：418-598-396

摘要：

Solid-state spin defects are promising platforms for quantum sensing, simulation, communication and computation. Despite the fast progress of the field, numerous issues remain to be addressed such as deleterious decoherence, low-fidelity control, and the lack of critical capabilities such as vector field sensing at nanoscale and arbitrary frequency field sensing. Additionally, a deeper understanding of the rich dynamics associated with the charge degrees of freedom of various defect states in the material host is necessary.
In this talk, I will present how do we tackle these different challenges for building better quantum sensors and simulators. I will begin with introducing quantum control based on modulated driving, which allows for the engineering of strong driving and the control of evolution modes. By utilizing modulated control techniques, we protect Rabi coherence by more than one order of magnitude in an ensemble of NV centers in diamond, and we simulate dynamical symmetries and characterize their selection rules using the coherence evolution of the system.

Inspired by the flexible quantum control in different frames, we develop protocols to improve quantum sensing performances. In particular, we develop a quantum mixer to convert off-resonant signal fields to resonant ones, achieving the sensing of arbitrary frequency vector fields. We develop a novel unbalanced echo sequence to extend the (nuclear) spin ensemble dephasing time to the single spin limit without perturbing the quantum information encoded in the sensor’s free evolution, paving the way for building better gyroscopes and memories.

Given that the charge states of defects play an important role due to their influence on the spin state and coherence, we use NV centers to probe the charge dynamics by characterizing the bath spectrum. We built a fast wide-field imaging setup integrated with a SPAD array to observe the process of charge transport under different optical illumination conditions, which tunes the dominant P1 defect spin density by a factor of 2. The tunability of spin concentration in time and spatial domain paves the way for their applications in simulating quantum many-body dynamics such as quantum hydrodynamics.

简历：

王国庆，2023年博士毕业于麻省理工学院，现为麻省理工学院博士后、麻省理工学院跨学科量子信息科学与工程学会（iQuISE）副主席。曾获普林斯顿大学量子奖、MathWorks奖学金。王国庆2018年本科毕业于北京大学7003全讯入口，曾获北京市、北京大学优秀毕业生等荣誉。主要研究领域为基于固态缺陷和冷原子体系的量子传感、量子模拟、量子计算和腔量子电动力学。代表性工作包括首次提出量子混频器、任意频率传感方案、非平衡自旋回波、量子自旋浓度的电荷调控等。已发表第一作者论文9篇，包括1篇PNAS，1篇PRX，2篇PRL、1篇Nano Letters等。

联系方式：bozhang_quantum@bit.edu.cn

邀请人： 张博

网 址：/

承办单位：物理学院、量子技术研究中心