Search for non-Abelian quantal phases and statistics

搜索非阿贝尔量子相和统计数据

• 批准号: EP/H017313/1
• 负责人: David Ritchie
• 金额: $ 15.75万
• 依托单位: University of Cambridge
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FH017313%2F1
• 关键词: Search; non; Abelian; quantal; phases

Quantum statistics and the spin and symmetry of wavefunctions are central to a quantum mechanical understanding of the world. Since the dawn of quantum mechanics it has been known that statistics distinguishes fermions from bosons due to symmetry with respect to interchange of two identical particles. In three spatial dimensions there are only two possible symmetries: the wave function of bosons is symmetric under permutation of particles while for fermions the wavefunction is antisymmetric. Two-dimensional systems are qualitatively different and the wavefunction can acquire any phase factor owing to interchange of two quasiparticles. These anyonic quasiparticles obey fractional statistics and arise in the context of the fractional quantum Hall effect. Yet more exotic phases and statistics has been envisioned, in which quasiparticle states are degenerate and their state vectors are multiplied by a unitary matrix rather than a phase factor as a result of quasiparticle interchange. In such a non-Abelian many-body systems exchange of two particles changes the state of all the particles in the condensate. Such rigidity of the wavefunction has lead to the idea of a fault-tolerant quantum computer with qubits based on non-Abelian states.While theoretically non-Abelian statistics and non-Abelian quantal phases have been predicted in many systems, no experiment to date has confirmed the existence of states with non-Abelian statistics. The most promising candidate - the filling factor v = 5/2 quantum Hall state is yet to be shown to be a non-Abelian state. Unlike the non-Abelian statistics, the non-Abelian quantal phase can already be a property of a single-particle wavefunction. We propose to explore the non-Abelian quantal phase in two-dimensional hole gases with total angular momentum J = 3/2 heavy hole states. The envisaged experiments on coupled quantum rings promise to show non- Abelian many-body effects and lead to the discovery of this elusive new state of matter. The proposed research involves advanced material growth, nanofabrication, rf investigation of small energy scales and a deep understanding of holes interactions. The Semiconductor Physics group at the Cavendish Laboratory, Cambridge University, headed by Professor David Ritchie, is one of a few places in the word where such an ambitious goal of detecting non-Abelian phases can be achieved. The group pioneered the key enabling technologies, such as MBE growth of high quality two dimensional gases and low temperature rf techniques. Prof. Leonid Rokhinson from Purdue University, USA, will bring expertise of many years of investigation of holes in GaAs, development of heterostructures especially tailored for nanofabrication techniques, and recently developed strain control techniques.

量子统计和波函数的自旋和对称性是量子力学理解世界的核心。自量子力学诞生以来，人们就知道，统计学将费米子与玻色子区分开来是因为两个相同粒子交换的对称性。在三维空间中，只有两种可能的对称性：玻色子的波函数在粒子排列下是对称的，而费米子的波函数是反对称的。由于两个准粒子的交换，二维系统性质不同，波函数可以获得任意的相因子。这些非离子准粒子服从分数统计，并出现在分数量子霍尔效应的背景下。然而，更奇异的相位和统计已经被设想，其中准粒子状态是简并的，并且它们的状态向量乘以酉矩阵而不是作为准粒子交换的结果的相位因子。在这样一个非阿贝尔多体系统中，两个粒子的交换改变了凝聚态中所有粒子的状态。波函数的这种刚性导致了基于非阿贝尔态的量子比特容错量子计算机的想法。虽然理论上非阿贝尔统计和非阿贝尔量子相位在许多系统中已经被预测，但迄今为止还没有实验证实存在非阿贝尔统计的状态。最有希望的候选者-填充因子v = 5/2的量子霍尔态尚未被证明是非阿贝尔态。与非阿贝尔统计不同，非阿贝尔量子相位已经可以是单粒子波函数的一个属性。我们研究了二维空穴气体中的非阿贝尔量子相位，其中重子态的总角动量为J = 3/2。设想中的耦合量子环实验有望显示非阿贝尔多体效应，并导致发现这种难以捉摸的新物质状态。拟议的研究涉及先进的材料生长，纳米纤维，小能量尺度的射频研究和空穴相互作用的深入理解。剑桥大学卡文迪什实验室的半导体物理小组，由大卫里奇教授领导，是世界上少数几个可以实现探测非阿贝尔相的雄心勃勃的目标的地方之一。该集团率先推出了关键的使能技术，如高质量二维气体的分子束外延生长和低温射频技术。来自美国普渡大学的Leonid Rokhinson教授将带来多年来对GaAs中空穴的研究、特别为纳米纤维技术定制的异质结构的开发以及最近开发的应变控制技术的专业知识。

项目成果

The fractional a.c. Josephson effect in a semiconductor-superconductor nanowire as a signature of Majorana particles

• DOI: 10.1038/nphys2429
• 发表时间: 2012-11-01
• 期刊: NATURE PHYSICS
• 影响因子: 19.6
• 作者: Rokhinson, Leonid P.;Liu, Xinyu;Furdyna, Jacek K.
• 通讯作者: Furdyna, Jacek K.