报告题目：On the advantage of barrier over tilt control of a singlet-triplet spin qubit

报告人：王欣(Sunny)，香港城市大学，助理教授

报告语言：中文

报告时间：2018年4月2日（星期一），上午10:00

报告地点：大学城理六栋220报告厅

报告摘要: Overcoming the charge noise is key to the realization of scalable quantum computation using spin qubits. It has been recently demonstrated that the effects of charge noise can be suppressed if operations of a singlet-triplet qubit are implemented using barrier control instead of the traditional tilt control. We have found, however, that for certain gates involving extensive x-rotations, barrier control offers little or no improvement when the nuclear noise is significant. Nevertheless, we introduce a new set of composite pulses that reduce gate times by up to 90%. Using these optimized pulses, the barrier control shows great advantages in randomized bench marking simulations, with the coherence time extended by about two orders of magnitude for experimentally relevant noises [1]. We have also performed microscopic calculations of a singlet-triplet qubit under the influence of an impurity. We have found that, the relative charge noise (charge noise divided by the exchange interaction), while generally believed to increase with increasing exchange interaction, actually decreases when the barrier control is implemented [2]. Moreover, we show that the exchange interaction of a singlet-triplet spin qubit confined in double quantum dots, when being controlled by the barrier method, is insensitive to a charged impurity lying along certain directions away from the center of the double-dot system. These directions differ from the polar axis of the double dots by the "magic angle", 54.7 degrees, a value previously found in atomic physics and nuclear magnetic resonance [3].

参考文献:

[1] C. Zhang, R.E. Throckmorton, X.-C. Yang, X. Wang, E. Barnes, S. Das Sarma, Phys. Rev. Lett. 118, 216802 (2017).

[2] X.-C. Yang, X. Wang, Phys. Rev. A 96, 012318 (2017).

[3] X.-C. Yang, X. Wang, Phys. Rev. A 97, 012304 (2018).

报告人简介:

王欣博士2005年于北京大学获得学士学位，2010年于哥伦比亚大学获得博士学位，2010-2015年于美国马里兰大学进行博士后研究，现为香港城市大学物理系助理教授，研究兴趣为理论量子物理与凝聚态物理，特别是基于量子点的量子信息处理和关联电子体系。