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Hybrid Superconductor-Semiconductor Devices for Majorana Fermion Detection

用于马约拉纳费米子检测的混合超导半导体器件

基本信息

批准号：
EP/J007137/1
负责人：
Edward Romans
金额：
$ 101.67万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2012
资助国家：
英国
起止时间：
2012 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FJ007137%2F1
关键词：
Hybrid Superconductor Semiconductor Devices Majorana

项目摘要

Our programme will involve looking for the experimental signature of so-far undetected particles known as Majorana fermions in hybrid semiconductor-superconductor devices that we will develop and fabricate. These will involve a semiconducting nanowire or quantum well heterostructure grown by molecular beam epitaxy (MBE) integrated with a superconducting thin film containing ultrasensitive Josephson-based measurement devices fabricated using electron-beam lithography. The devices will be operated at ultra-low temperatures, down to 15 mK. Once Majorana fermions can be detected, we will design and fabricate further more complicated superconductor-semiconductor structures and circuits to enable us to demonstrate that Majorana fermions can be transported and stored in an analogous way to how conventional electrons or holes are controlled in the operation of all present day electronic circuits such as computer processors. There is currently huge interest in Majorana fermions because it is likely they will be very imporant for future quantum information technology leading to the development of faster, more powerful parallel computers in the future. At the moment the major bottleneck in the develop of such quantum computers is decoherence, where interference from the neighbouring environment to the device, or defects in the device materials, lead to a critical loss of information over a very short timescale. If quantum computers can be built based on the manipulation of Majorana fermions then the qubits (the quantum bits used to store information) can be made from a pair of widely separated Majorana fermions. These would be insensitive to the effect of localised sources of decoherence and this would allow the realisation of a robust quantum computer.The existence of Majorana fermions was first proposed in 1937 by Ettore Majorana who showed by modifying Dirac's existing theory of conventional fermions (particles with half-integer spin such as electrons) that there could exist a class of particles that are their own antiparticles, very unlike conventional fermions. Despite the fact that they are widely believed to exist, no-one has so far experimentally proved this. The reason is that unlike conventional fermions they do not satisfy the usual rules of charge conservation and cannot be detected by simple electrical means. Our programme will involve investigating systems where the interaction between the magnetic properties of certain semiconductors in contact with a superconductor has been theoretically shown to provide the necessary conditions for Majorana fermions to be created as elementary excitations of the system. In addition to being a key component for producing Majorana fermions, the superconductor can also be used to fabricate Josephson-based sensors which display macroscopically observable quantum effects that can be specifically attributed to Majorana fermions. So by combining ultraclean semiconductor structures with superconducting devices we will have the ideal combination of factors to detect Majorana fermions for the first time.

我们的计划将包括在我们将开发和制造的混合半导体超导器件中寻找迄今未被检测到的粒子的实验签名，即Majorana费米子。这将涉及通过分子束外延(MBE)与超导薄膜集成生长的半导体纳米线或量子阱异质结构，超导薄膜包含使用电子束光刻制造的基于约瑟夫森的超灵敏测量设备。这些设备将在超低温下运行，最低温度可达15MK。一旦可以检测到Majorana费米子，我们将设计和制造更复杂的超导体-半导体结构和电路，使我们能够证明Majorana费米子可以通过类似于在所有现代电子电路(如计算机处理器)的运行中如何控制传统电子或空穴的方式来传输和存储。目前人们对Majorana费米子非常感兴趣，因为它们很可能对未来的量子信息技术非常重要，从而导致未来更快、更强大的并行计算机的发展。目前，这类量子计算机发展的主要瓶颈是退相干，即来自邻近环境对设备的干扰，或设备材料中的缺陷，导致在非常短的时间内严重丢失信息。如果量子计算机可以建立在对Majorana费米子的操纵基础上，那么量子比特(用于存储信息的量子比特)可以由一对相距很远的Majorana费米子制成。这些粒子对局域退相干源的影响不敏感，这将允许实现强大的量子计算机。Majorana费米子的存在是由Ettore Majorana在1937年首次提出的，他通过修改狄拉克现有的传统费米子(具有半整数自旋的粒子，如电子)理论表明，可能存在一类粒子，它们自己是反粒子，与传统费米子非常不同。尽管人们普遍认为它们是存在的，但到目前为止还没有人用实验证明这一点。原因是，与传统的费米子不同，它们不满足通常的电荷守恒规则，也不能通过简单的电学手段进行检测。我们的计划将包括研究这样的系统，在这些系统中，某些半导体与超导体接触的磁性之间的相互作用在理论上被证明是为产生马约拉纳费米子作为系统的基本激发提供了必要条件。除了是生产Majorana费米子的关键部件外，这种超导体还可以用来制造约瑟夫森传感器，这些传感器显示了宏观上可观察到的量子效应，这些效应可以特别归因于Majorana费米子。因此，通过将超净半导体结构与超导器件相结合，我们将拥有首次探测马约拉纳费米子的理想因素组合。