Exploring nanowire structures for quantum information - a route to discoveries and new technological applications

经典计算机（CC）使用经典物理将信息编码为二进制位，而量子计算机依靠量子力学定律（QM）以量子位处理信息——量子位可能由于叠加而同时处于两种状态，许多这样的量子位可以通过纠缠形成强相关系统，表现为单个系统。这样的QM系统本质上比cc更强大，并且有足够大的量子位，可以解决cc难以解决的问题。寻找一个完美的平台，同时满足快速量子控制、长相干时间和数千量子位的可扩展性的要求，仍然是一个相当有趣的话题。最近，一种基于半导体(S)纳米线（NW）异质结构（HS）的新平台出现了，量子比特显示了量子点中单自旋的最快电自旋操作时间。此外，马约拉纳费米子（MFs）的第一个特征（MFs是它们自己的反粒子，代表拓扑量子比特的构建块）最近在这样的NWs中被报道。然而，这些系统仍处于起步阶段，通常只在稀释冰箱温度下起作用。NW HS带来：(a)径向和纵向HS的材料选择几乎是无限的，因为随着它们的生长，应变可以通过无限制的变形来缓解；(b)可以定义多个局部金属或超导体（SC）门，以及全局后门，以提供可扩展的量子比特系统。本提案研究了基于nw的方案，解决了当前可扩展QC平台方案的缺点。基于MF的量子比特，通过拓扑保护，应该几乎不受基于环境的退相干的影响。然而，为了容纳它们，弹道(B) NW HS是关键-我们已经证明了对表面状态占用和后向散射的控制，以产生最先进的B- nws；有足够质量的B-NWs，长而薄的NWs可以用来增强免疫力。我们建议利用我们最近关于高温SC （HTSC）的近似SC的第一份报告，有可能将该技术带到接近ln2的温度-这是相当新的东西。接下来我们将探索可扩展的系统，它可以扩展到多量子位系统。我们还将探索在高温下使用HTSC/NW-HS系统进行纠缠光子对的门控辐射发射（和双光子吸收）的新可能性——这种设备可以为可扩展的量子处理应用提供实现“飞行”量子比特的手段。我们还将探索一种基于自组装电子晶格（称为早期维格纳晶格）的致密量子比特寄存器的替代平台。这种纠缠态具有反平行自旋对，可用于信息传输、计算和存储。

Classical computers (CC) use classical physics to encode information in binary bits while quantum computers rely on the laws of quantum mechanics (QM) to process information in qubits – qubits may simultaneously be in two states due to superposition, and many such qubits can form strongly correlated systems through entanglement, behaving as a single system. Such QM systems are inherently more powerful than CCs, and with sufficiently large numbers of qubits, can solve problems that are intractable with CCs. The search for a perfect platform that simultaneously satisfies requirements of fast quantum control, long coherence times and scalability to thousands of qubits remains a topic of considerable interest. Recently, a new platform based on semiconductor (S) nanowire (NW) heterostructures (HS) has emerged, with qubits showing the fastest electrical spin manipulation times for single spins in QDs. Moreover, the first signatures of Majorana fermions (MFs), which are their own antiparticles and represent the building blocks for topological qubits, have been very recently reported in such NWs. However, these systems are still in their infancy and typically only function in dilution fridge temperatures. NW HS bring: (a) a virtually unlimited choice of materials for both radial and longitudinal HSs as strain may be relieved by unconfined deformation as they grow, and (b) multiple local metal or superconductor (SC) gates may be defined, together with a global back-gate, to provide scalable qubit systems. This proposal examines NW-based schemes addressing shortcomings of current schemes for a scalable QC platform. MF based qubits, through topological protection, should be virtually immune to environment-based decoherence. However, to host them, ballistic (B) NW HS are key - an area where we have demonstrated control over surface state occupation and backscattering to yield state of the art B-NWs; with sufficient quality B-NWs, long thin NWs can be used to enhance immunity. We propose to harness our recent first reports on proximitized SC with high temperature SCs (HTSC), to potentially bring the technology to near-LN2 temperatures – something quite new. Next we will explore scalable systems which can be extended into multi-qubit systems. We will also explore the novel possibility of using HTSC/NW-HS systems for gate controlled radiative emission (and two-photon absorption) of entangled photon pairs at elevated temperatures – such devices could provide the means to implement “flying” qubits for scalable quantum processing application. We will also explore an alternative platform for dense qubit registers based on self-assembled electron lattices known as the incipient Wigner lattice. This state with entangled e' (spin antiparallel) pairing, can be explored for its' potential for information transmission, computation and memory.