拓扑量子态的制备和调控

Much attention has been paid recently to topological quantum states, through which fault-tolerant quantum computers are promising to be built. The key to realize topological quantum computation is to identify and manipulate the topological quantum states’ quasiparticles that obey non-Abelian fractional statistics, such as the Majorana fermions. In this proposal, we plan to utilize innovated experimental schemes and our state of the art experimental equipment to study the key issues facing the topological quantum computation, from the following two major directions: (1) Utilizing the techniques that we pioneered in the fabrication of hybrid devices of s-wave superconductor and topological insulator, to explore the possibilities of realizing px+ipy superconductivity in this type of devices, constructing superconducting quantum interference devices to create Majorana fermions, and even manipulating them. (2) Utilizing our experiment system of world-record ultra-low electron temperature that was built by ourselves, to study the quasiparticle statistics and interference effect of 5/2 fractional quantum state in a high mobility two-dimensional electron gas, hopefully it would provide cleaner data that help to clarify some important issues, such as whether the fractional charge of the 5/2 state is e/2 or e/4, and whether the p-wave superconductivity can be observable for this state.

拓扑量子物态是一种近来倍受关注的量子态。通过对其的调控，有望实现免退相干的拓扑量子计算。所涉及到的核心物理问题是，能否找到并调控拓扑量子态之满足非阿贝尔分数统计的准粒子激发，比如Majorana费米子。在本研究计划中，我们拟运用有特色的实验方案和领先的实验条件，从当今这一领域的两个主流方向上，对拓扑量子计算涉及到的关键物理问题展开研究：（1）利用目前我们领先的、基于s波超导体与拓扑绝缘体之间邻近效应的超导量子干涉器制备技术，探索产生px+ipy拓扑超导态，并形成和操控Majorana费米子。（2）运用自主建立的具有当今最低电子温度的实验系统，对高迁移率二维电子气5/2分数量子霍尔态之准粒子的干涉效应和统计性质开展研究，期望以干净的实验数据澄清分数电荷是e/2、还是e/4并配对形成p波超导等问题。

拓扑量子物态是一种近来倍受关注的量子态，2016年的诺贝尔物理奖颁给了拓扑量子物态的理论研究。制备拓扑量子物态，寻找并编织Majorana费米子，是该研究领域激烈竞争的热点问题。我们在本项目的资助下，运用有特色的实验手段，瞄准核心问题，通过4年的努力在这一领域取得了一些重要的阶段性进展，包括在基于三维拓扑绝缘体的射频超导量子干涉器上发现了Majorana费米子导致的4pi周期，以及在基于二维电子气的法布里－珀罗干涉器上看到了整数量子霍尔台阶边缘的库伦振荡。一些重要进展尚未能发表，但已经引起了学术界的重视，被国际著名理论组认为是领域内的标志性工作之一。此外，在拓扑量子物态的其它研究方面，我们与清华大学薛其坤团队合作首次发现了量子反常霍尔效应，还与复旦大学金晓峰小组合作，利用Bi/Ni双层膜首次给出了手性拓扑超导电性存在的证据。