Collaborative Research: Non-Ideal Majorana Fermions: A Practical Approach to Topological Quantum Computation

合作研究：非理想马约拉纳费米子：拓扑量子计算的实用方法

• 批准号: 2014157
• 负责人: Sumanta Tewari
• 金额: $ 15万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2014157&HistoricalAwards=false
• 关键词: Collaborative; Research; Non; Ideal; Majorana

The main obstacle to quantum computation is the “noise” affecting the basic units of a quantum computer – the so-called qubits – as a result of their weak, but nonzero coupling to the environment. Since this coupling is essentially local, a promising approach to overcoming the noise problem is to encode the information using topological quantum phenomena – robust global properties characterizing certain types of quantum systems that are immune to local perturbations. A promising platform for realizing robust topological qubits is based on a special kind of quantum quasiparticle called a Majorana fermion or Majorana zero mode (MZM). Recent theoretical studies by the PIs and other groups indicate that experiments may have already uncovered non-ideal versions of MZMs, the so-called quasi-Majorana modes. In this project the PIs will examine fundamental aspects of topological protection and practical design questions related to maximizing qubit lifetime and minimizing noise rates in quantum devices with non-ideal Majorana fermions. With most of the ongoing research in the field focusing on ideal Majorana fermions, which in practice may be hard to realize, the present studies will be critical to engineering the first generation of topological qubits using what may be already available, namely, non-ideal Majorana fermions. The project will serve the national interest and promote the NSF mission of progress of science by deepening our understanding of topological quantum matter in condensed matter systems and investigating the feasibility of topological quantum computation based on experimentally available devices. The project will provide excellent education and training opportunities to undergraduate and graduate students at Clemson University, including economically disadvantaged students and underrepresented minorities who constitute a significant percentage of the student population. This project is jointly funded by the Quantum Information Science Program (Physics Division), and the Established Program to Stimulate Competitive Research (EPSCoR). Majorana zero modes (MZMs) in semiconductor-superconductor (SM-SC) nanowire heterostructures are currently being investigated as possible building blocks for topological qubits in a future quantum computer. Theoretical studies by the PIs and others have shown that much of the parameter space of the experimentally investigated SM-SC heterostructures is in fact occupied by so-called quasi-Majorana zero modes, which are separated from each other by a length scale well below the nanowire length. Since the principle of fault tolerance in topological quantum computation (TQC) depends critically on the non-local encoding of quantum information using topological MZMs separated by the length of the nanowire, this situation presents a major problem for the feasibility of TQC, as quasi-Majoranas do not enjoy sufficient topological protection for fault-tolerant qubit operations. Nonetheless, quasi-Majoranas are likely to be present in the first generation of Majorana-based qubit devices either by design, or by accident. This project fills the critical void created by the near absence of studies of topological qubit designs and schemes for braiding and error correction when the constituent building blocks are quasi-Majoranas, rather than ideal topological MZMs. The PIs will perform analytical and numerical research with the following intellectual goals: (1) Designing and modeling SM-SC qubit devices based on controllable quasi-Majorana zero modes, (2) Understanding and characterizing the key physical processes that control the quasi-Majorana qubit lifetimes, and (3) Error analysis in measurement-only TQC schemes with quasi-Majorana zero modes. The overarching goal is to investigate the feasibility of fault tolerant TQC with quasi-Majorana zero modes (rather than ideal MZMs) and to better understand practical aspects of engineering Majorana-based topological qubits.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

量子计算的主要障碍是影响量子计算机基本单元的“噪声”-所谓的量子比特-由于它们与环境的弱但非零耦合。由于这种耦合本质上是局部的，克服噪声问题的一种有希望的方法是使用拓扑量子现象对信息进行编码--拓扑量子现象是某些类型的量子系统的鲁棒全局特性，它们不受局部扰动的影响。一个很有前途的平台，实现强大的拓扑量子比特是基于一种特殊的量子准粒子称为马约拉纳费米子或马约拉纳零模式（MZM）。PI和其他小组最近的理论研究表明，实验可能已经发现了MZM的非理想版本，即所谓的准马约拉纳模式。在这个项目中，PI将研究拓扑保护的基本方面，以及与最大化量子比特寿命和最小化具有非理想马约拉纳费米子的量子设备中的噪声率相关的实际设计问题。由于该领域正在进行的大部分研究都集中在理想的马约拉纳费米子上，这在实践中可能很难实现，因此目前的研究对于使用可能已经存在的东西（即非理想的马约拉纳费米子）设计第一代拓扑量子比特至关重要。该项目将通过加深我们对凝聚态系统中拓扑量子物质的理解和研究基于实验可用设备的拓扑量子计算的可行性来服务于国家利益并促进NSF的科学进步使命。该项目将为克莱姆森大学的本科生和研究生提供良好的教育和培训机会，包括经济上处于不利地位的学生和在学生人口中占很大比例的代表性不足的少数民族。该项目由量子信息科学计划（物理部）和刺激竞争研究的既定计划（EPSCoR）共同资助。超导-超导（SM-SC）纳米线异质结构中的马约拉纳零模（MZM）目前正被研究作为未来量子计算机中拓扑量子位的可能构建块。PI和其他人的理论研究表明，实验研究的SM-SC异质结构的大部分参数空间实际上被所谓的准马约拉纳零模式占据，这些模式彼此分开的长度尺度远低于纳米线长度。由于拓扑量子计算（TQC）中的容错原理严重依赖于使用由纳米线长度分隔的拓扑MZM对量子信息进行非局域编码，因此这种情况对TQC的可行性提出了一个主要问题，因为准马约拉纳不享有足够的拓扑保护以进行容错量子位操作。尽管如此，准马约拉纳可能会出现在第一代基于马约拉纳的量子比特设备中，无论是设计还是意外。该项目填补了由于几乎没有拓扑量子位设计研究以及编织和纠错方案而造成的关键空白，当组成构件是准Majoranas而不是理想的拓扑MZM时。PI将进行分析和数值研究，其智力目标如下：（1）基于可控准马约拉纳零模式设计和建模SM-SC量子比特器件，（2）理解和表征控制准马约拉纳量子比特寿命的关键物理过程，以及（3）具有准马约拉纳零模式的仅测量TQC方案的误差分析。总体目标是研究具有准马约拉纳零模（而不是理想的MZM）的容错TQC的可行性，并更好地理解工程马约拉纳拓扑量子位的实际方面。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Decoupling intranode and internode scattering in Weyl fermions

• DOI: 10.1103/physrevb.107.115161
• 发表时间: 2023-03
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: G. Sharma;S. Nandy;Karthik Raman;S. Tewari

Chiral anomaly induced nonlinear Nernst and thermal Hall effects in Weyl semimetals

• DOI: 10.1103/physrevb.105.125131
• 发表时间: 2020-12
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Chuanchang Zeng;S. Nandy;S. Tewari

Partially separated Majorana modes in a disordered medium

无序介质中部分分离的马约拉纳模式

• DOI: 10.1103/physrevb.105.205122
• 发表时间: 2022
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Zeng, Chuanchang;Sharma, Girish;Tewari, Sumanta;Stanescu, Tudor
• 通讯作者: Stanescu, Tudor

Quantum oscillations as a robust fingerprint of chiral anomaly in nonlinear response in Weyl semimetals

• DOI: 10.1103/physrevb.107.l081107
• 发表时间: 2022-03
• 期刊: Physical Review B
• 影响因子: 3.7
• 作者: Chuanchang Zeng;S. Nandy;Pu Liu;S. Tewari;Yugui Yao

Chiral anomaly induced nonlinear Hall effect in semimetals with multiple Weyl points

• DOI: 10.1103/physrevb.104.205124
• 发表时间: 2021-11-22
• 期刊: PHYSICAL REVIEW B
• 影响因子: 3.7
• 作者: Nandy, Snehasish;Zeng, Chuanchang;Tewari, Sumanta
• 通讯作者: Tewari, Sumanta