A quantum resonator in a finite-temperature state is featured with a significant occupation over Fock states of a high excitation number. During the “free-evolution and measurement” cycles, we use various methods to optimize the measurement-based cooling in terms of the average-population reduction rate, the success probability, the target-state fidelity, and the numbers of running cycles. We can reduce the average population of the target resonator by 4 orders in magnitude under less than 20 rounds of measurements with a success probability of about 30%. The scheme of projective measurement can be generalized to POVM, based on which a measurement-based control can be synthesized. By transforming a system from a thermal state to a population-inverted state, we can modify an energetic yet unusable system to be a quantum battery with a near-unit ratio of ergotropy (usable energy under unitary transformation) to energy. Through our works, quantum measurement becomes an interesting tool to shape quantum systems.

References:

[1] J. Yan and J. Jing*, Simultaneous cooling by measuring one ancillary system, Physical Review A 105, 052607 (2022).

[2] J. Yan and J. Jing*, Optimizing measurement-based cooling by reinforcement learning, Physical Review A 106, 033124 (2022).

[3] J. Yan and J. Jing*, Charging by quantum measurement, Physical Review Applied 19, 064069 (2023).

报告人简介：

景俊，上海交通大学物理系本科（1998-2002）、硕博连读（2002-2007），2007年获理论物理博士学位。上海大学物理系讲师（2007-2009）、副教授（2009-2014）。吉林大学原子与分子物理研究所教授、博士生导师（2014-2017）。浙江大学物理学院光学与量子信息研究所教授、博士生导师（2017-至今）。曾任美国史蒂文斯理工学院研究助理（2010-2012）；西班牙巴斯克大学理论物理系、美国纽约大学水牛城分校物理系（2013-2014）、北京计算科学中心（2015-2016）、香港理工大学应用物理系（2016）访问学者。曾获2009年度上海市教育委员会&上海市教育发展基金会“晨光”计划学者称号。主要致力于开放量子系统动力学、量子几何相、量子退相干、量子光学系统与固态量子系统的状态调控、以及量子测量基本理论方面的研究。主持国家自然科学基金面上基金三项、青年基金一项。

景俊