Nonclassicalities and Quantum Control at the Nanoscale

纳米尺度的非经典性和量子控制

• 批准号: EP/J014664/1
• 负责人: Sougato Bose
• 金额: $ 148.62万
• 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%2FJ014664%2F1
• 关键词: Nonclassicalities; Quantum; Control; Nanoscale

While the quantum behaviour of atomic-scale objects is no surprise, it would be absolutely arresting to find the same weird features being displayed by much more macroscopic objects. As quantum physics underpins much of our everyday technology, the importance of stretching its domain of applicability can hardly be overemphasized. For example larger systems (easier to control), could play a key role in quantum information processing.Recently, a number of new methods have become available to probe the quantum nature, in other words the "nonclassicality", of nanoscale objects. One of the foremost is the interference of freely moving objects in which one of the Co-Is is an expert. Another is an early idea by the PI to probe superpositions with confined (stationary) nanoscale objects by controlling them with an auxiliary quantum system. While such schemes are yet to be realised, they have suddenly started to look quite feasible in view of a clever idea by one of the Co-Is, namely to optically levitate such objects, which largely isolates them from their environments and prevents decoherence -- a phenomenon that causes the irreversible demise of quantum features. In the above backdrop, we propose a project that aims at coupling spins to nanoscale objects to control their quantum motion and perform complementary tests of the nonclassicality of free and trapped mesoscale objects. Theory led by the PI and a Co-I, both experts in somewhat complementary areas of quantum optics and information, will outline the appropriate strategies for the above experiments, as well as explore the exploitation of these systems for the eventual benefit of quantum information processing. As opposed to other world-wide efforts that we are aware of, we will avoid both extensive cooling and preparing high quality optical cavities. This strategy is expected to give us significant competitive advantage in probing several quantum attributes for which the above are not really necessary. An experimental Co-I in spin manipulation will enable us to levitate a spin bearing nano object and couple the spin to its motion. The presence of expert Co-Is in both interference and levitation is going to enable us to access two promising yet complementary techniques of probing the macroscopic limits of quantum mechanics with the same or similar objects. Significant milestones for levitated objects include probing the validity of the superposition principle and quantum commutation relations for these systems, single shot spin readout through their motion, their entanglement and their potential as quantum walkers and registers for quantum computation. For free objects, we plan to enhance the mass of objects in interferometry by several orders of magnitude, perform tomography of their highly nonclassical states during interferometry, as well as perform precision spin measurements through the interferometry of spin bearing nano particles. The feasibility of more challenging experiments for the future will also be explored within the project, such as a Stern-Gerlach interferometry to probe superpositions of free objects and the usage of a levitated object as a mediator for entangling spins.The ultimate ramifications of the project are expected to be in two directions: the fundamental question of whether there are any limits to thevalidity of quantum principles when one applies them to nanoscale objects, and the applied issue of the usage of such systems in informationtechnology. Such research is also expected to raise public interest in science by highlighting the counterintuitive quantum behaviour ofmacroscopic systems.

虽然原子尺度物体的量子行为并不令人惊讶，但如果发现更多宏观物体显示出同样的奇怪特征，那将是绝对引人注目的。由于量子物理是我们日常技术的基础，扩大其适用范围的重要性怎么强调都不为过。例如，更大的系统(更容易控制)可以在量子信息处理中发挥关键作用。最近，已经有许多新方法可以用来探测纳米级物体的量子本质，换言之，“非经典”。其中最重要的是自由移动物体的干扰，其中一名合作伙伴是这方面的专家。另一种是PI提出的早期想法，即通过辅助量子系统控制受限(静止)纳米级物体的叠加。虽然这样的方案还没有实现，但鉴于其中一个合作伙伴提出的一个聪明的想法，它们突然开始变得相当可行，即让这些物体光学悬浮，这在很大程度上将它们与环境隔离，并防止退相干--这一现象导致量子特征的不可逆转消亡。在上述背景下，我们提出了一个项目，旨在将自旋耦合到纳米尺度的物体上，以控制它们的量子运动，并对自由和囚禁中尺度物体的非经典性质进行互补测试。由PI和A Co-I领导的理论，两位在量子光学和信息领域具有一定互补性的专家，将概述上述实验的适当策略，并探索利用这些系统最终受益于量子信息处理。与我们所知道的其他世界范围内的努力不同，我们将避免广泛的冷却和准备高质量的光学腔。这一策略预计将在探索上述几个不是真正必要的量子属性方面给我们显着的竞争优势。一个实验性的自旋操纵Co-I将使我们能够悬浮一个带有自旋的纳米物体，并将自旋与其运动相耦合。在干涉和悬浮中专家的存在将使我们能够使用两种很有前途但互补的技术来探测相同或相似对象的量子力学的宏观极限。悬浮物的重要里程碑包括探索这些系统的叠加原理和量子对易关系的有效性，通过它们的运动单次自旋读出，它们的纠缠，以及它们作为量子步行者和量子计算登记器的潜力。对于自由物体，我们计划将干涉测量中的物体质量提高几个数量级，在干涉测量过程中对其高度非经典状态进行层析成像，以及通过自旋轴承纳米粒子的干涉测量进行精确的自旋测量。该项目还将探索未来更具挑战性的实验的可行性，例如使用斯特恩-格拉赫干涉术来探测自由物体的叠加，以及将悬浮物体用作纠缠自旋的媒介体。该项目的最终结果预计将在两个方向上：当人们将量子原理应用于纳米级物体时，量子原理的有效性是否有任何限制的根本问题，以及此类系统在信息技术中的应用问题。这类研究还有望通过突出宏观系统违反直觉的量子行为，提高公众对科学的兴趣。

项目成果

Correlated random walks caused by dynamical wavefunction collapse

动态波函数崩溃引起的相关随机游走

• DOI: 10.48550/arxiv.1411.6921
• 发表时间: 2014
• 作者: Bedingham D

Robust stationary mechanical squeezing in a kicked quadratic optomechanical system

• DOI: 10.1103/physreva.89.023849
• 发表时间: 2014-02-28
• 期刊: PHYSICAL REVIEW A
• 影响因子: 2.9
• 作者: Asjad, M.;Agarwal, G. S.;Vitali, D.
• 通讯作者: Vitali, D.

Correlated random walks caused by dynamical wavefunction collapse.

• DOI: 10.1038/srep13380
• 发表时间: 2015-08-25
• 期刊: Scientific reports
• 影响因子: 4.6
• 作者: Bedingham DJ;Ulbricht H
• 通讯作者: Ulbricht H

Testing the quantum superposition principle in the frequency domain

在频域测试量子叠加原理

• DOI: 10.48550/arxiv.1309.5889
• 发表时间: 2013
• 作者: Bahrami M

Proposal for a Noninterferometric Test of Collapse Models in Optomechanical Systems

• DOI: 10.1103/physrevlett.112.210404
• 发表时间: 2014-05-29
• 期刊: PHYSICAL REVIEW LETTERS
• 影响因子: 8.6
• 作者: Bahrami, M.;Paternostro, M.;Ulbricht, H.
• 通讯作者: Ulbricht, H.