DECOHERENCE and DISENTANGLEMENT in MACROSCOPIC SYSTEMS

宏观系统中的退相干和解缠结

• 批准号: RGPIN-2019-05582
• 负责人: Stamp, Philip
• 金额: $ 2.48万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=685204
• 关键词: DECOHERENCE; DISENTANGLEMENT; MACROSCOPIC; SYSTEMS

Physics is currently built on Quantum Mechanics, which describes small systems, and General Relativity, which describes massive bodies. Each theory has had extraordinary success. Until now it has been impossible to confront them experimentally.*** In recent years experiments have pushed Quantum Mechanics into the macroscopic realm. Quantum computers - large arrays of 'qubits' made from either solid-state materials or atomic spins - involve macroscopic numbers of atoms. The biggest problem confronting quantum computation is 'decoherence', ie., the mechanism whereby the delicate correlations between qubits are destroyed by the environment around them, ruining the computation. Thus we need a better understanding of the mechanisms involved in decoherence, and how to suppress them.*** Decoherence mechanisms are also linked to fundamental questions in physics. Experiments involving quantum superpositions in optomechanical devices will soon be possible with masses larger than the Planck mass of 20 micrograms. These will test key features of quantum gravity - and reveal whether either quantum mechanics or General Relativity breaks down. Some argue that an 'intrinsic decoherence' mechanism in Nature will then intervene; others that decoherence may lead to the emergence of classical physics.*** This project will develop a theory of the dynamics of decoherence mechanisms, for quantum computation and for tests of quantum gravity. The mechanisms include conventional couplings to photons, phonons, electrons, defects, nuclear and paramagnetic impurities, and gravitational degrees of freedom, as well as more exotic mechanisms. The 'conventional' theory will be applied to quantum computation designs involving arrays of spins in semiconductors as well as in certain rare earth and transition metal systems. It will also be used to look at conventional gravitational decoherence mechanisms, relevant to gravitational wave detectors. *** The more exotic mechanisms include the recent 'correlated worldline' theory of quantum gravity, as well as semiclassical theories of gravity - these theories, and the predicted breakdown of quantum mechanics caused by gravity, will be tested on optomechanical systems. Conventional decoherence for these systems will also be calculated, to separate this from the exotic mechanisms.*** The most obvious spinoffs/outcomes will be (i) the ability to suppress decoherence in quantum computation - such results are crucial to the design of practical quantum computers - and (ii) quantitative predictions for fundamental experiments in quantum gravity. Other spinoffs will include a better understanding of quantum phase transitions (strongly influenced by decoherence), of great interest for the theory of strongly-correlated condensed matter systems.*** The most obvious benefit to Canada is in practical quantum computation development - a key future technology, where research like this will be essential. **

物理学目前建立在描述小系统的量子力学和描述大质量物体的广义相对论的基础上。每一种理论都取得了非凡的成功。到目前为止，还不可能在实验上与它们对抗。*近年来，实验将量子力学推向了宏观领域。量子计算机--由固态材料或原子自旋组成的大型量子比特阵列--涉及宏观的原子数量。量子计算面临的最大问题是“消相干”，即量子比特之间微妙的相关性被周围环境破坏的机制，从而破坏了计算。因此，我们需要更好地了解退相干的机制，以及如何抑制它们。*退相干机制也与物理学中的基本问题有关。在光学机械设备中进行量子叠加的实验将很快成为可能，其质量将大于20微克的普朗克质量。这些将测试量子引力的关键特征，并揭示量子力学或广义相对论是否会崩溃。一些人认为，自然界中的一种内在退相干机制会介入；另一些人认为，退相干可能会导致经典物理学的出现。*这个项目将发展一种关于退相干机制动力学的理论，用于量子计算和量子引力测试。这些机制包括与光子、声子、电子、缺陷、核和顺磁杂质的传统耦合，以及引力自由度，以及更奇特的机制。这一“传统”理论将应用于量子计算设计，包括半导体中的自旋阵列，以及某些稀土和过渡金属系统。它还将被用来研究与引力波探测器相关的传统引力消相干机制。*更奇特的机制包括最新的量子引力相关世界线理论，以及半经典引力理论--这些理论以及预测的由重力导致的量子力学崩溃，将在光学机械系统上进行测试。还将计算这些系统的传统消相干，以将其与奇异的机制分开。*最明显的副产品/结果将是(I)在量子计算中抑制消相干的能力--这样的结果对实际量子计算机的设计至关重要--以及(Ii)量子引力基础实验的定量预测。其他衍生产品将包括更好地理解量子相变(受到退相干的强烈影响)，这对强关联凝聚态系统的理论非常感兴趣。*加拿大最明显的好处是在实际量子计算开发方面--这是未来的一项关键技术，这样的研究将是必不可少的。**