Optimal control for robust ion trap quantum logic

稳健离子阱量子逻辑的优化控制

• 批准号: EP/P024890/1
• 负责人: Richard Thompson
• 金额: $ 141.52万
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FP024890%2F1
• 关键词: Optimal; control; robust; ion; trap

Minuscule objects that follow the laws of quantum mechanics have the promise of carrying out delicate tasks fundamentally better than macroscopic objects that are bound by the laws of Newtonian classical mechanics. The superposition principle permits individual quantum mechanical objects to follow multiple trajectories in parallel, and pairs (or larger collections) of such objects can be entangled with each other, such that a measurement on one object affects the properties of the other objects even if they are far apart. The superposition principle and entanglement provide the basis for applications like precision metrology or quantum computation that are expected to revolutionise our technology, just like the steam engine or the advent of electricity has done in the past.The explicit utilisation of these quantum mechanical effects for useful applications, however, requires extremely accurate control over quantum objects and their interaction with their surroundings. Trapped ions are one of the leading systems in this context. Selected energy levels of an ion define a qubit, which is the elementary unit of a quantum computer, just like a classical computer is comprised of many bits. Confined by electric and magnetic trapping fields, ions can be manipulated with laser beams, and the collective motion of strings of ions enables the exchange of information between several qubits. For this to work with high accuracy it is typically required to cool the ions to a temperature close to absolute zero. Once such a temperature has been reached, one makes use of the fact that any manipulation of the ions changes their motional state in order to implement logical operations that define the elementary building blocks of a quantum algorithm.Since the ions' motion is easily heated by its room-temperature environment, the intentionally induced changes in the motional state can be accompanied by uncontrolled heating processes, and any deviation from the desired change in motional state results in reduced accuracy of the operations being implemented. The goal of the present project is the development and experimental implementation of laser control of trapped ions that achieves desired operations with high accuracy and robustness in the presence of undesired heating and other experimental imperfections.In a strong collaboration between theory and experiment, control sequences will be developed and tested in a novel ion trap whose parameters can be varied over a wide range. The ability to tune the strength of the interaction between qubits and motion (the Lamb-Dicke parameter) and the strength of thermal effects will allow us to identify the control strategies that deal with each type of imperfection in an ideal fashion. Most current experiments are conducted with a rather weak interaction between qubits and motion, but we aim at the realisation of logical operations between qubits that interact strongly with the motion. The increased manipulation speed that comes with the strong interaction increases the number of logical operations that can be implemented within the limits imposed by finite decoherence time, and as such will help us to move from proof-of-principle experiments to a practical application.The immediate goal of our work is the improvement in the control of trapped ions for quantum computing, but the advanced control techniques we will develop directly apply to any type of coherent manipulation of trapped ions. Since strong interactions between qubits are beneficial for fast information transfer but challenging for the implementation of accurate manipulations in essentially any quantum system, the control techniques to be developed are expected to find application in a broad range of other systems in quantum optics and quantum electronics.

遵循量子力学定律的微小对象具有比受牛顿古典力学定律束缚的宏观对象更好地执行精致的任务。叠加原理允许单个量子机械对象并联遵循多个轨迹，并且这些对象的成对（或较大的集合）可以彼此纠缠，因此，即使一个对象的测量值也会影响其他对象的属性，即使它们是远距离的。叠加原理和纠缠为诸如精确度量或量子计算等应用提供了基础，这些应用有望彻底改变我们的技术，就像过去的蒸汽机或电力的出现一样。但是，这些量子机械效应的明确利用需要对有用的应用，需要对量子对象及其与周围环境的相互作用极为准确。在这种情况下，被困的离子是领先的系统之一。离子的选定能级定义了一个量子，这是量子计算机的基本单元，就像经典计算机由许多位组成一样。由电气和磁陷阱限制在限制的地方，可以用激光束操纵离子，而离子字符串的集体运动可以在几个量子位之间交换信息。为此，通常需要将离子冷却到接近绝对零的温度。一旦达到这样的温度，人们就会利用一个事实，即对离子进行任何操作会改变其运动状态，以实施逻辑操作，以定义量子算法的基本构建块。之后，离子的运动很容易被其房间温度的环境所带来的，并有意诱导的任何变化都可以逐步散布，并逐渐逐渐散布，并逐渐变化，并逐渐变化，并散布在不断变化实施操作的准确性降低。本项目的目的是对被困离子的激光控制的开发和实现，在存在不希望的加热和其他实验缺陷的情况下，以高准确性和鲁棒性实现所需的操作。在理论与实验之间进行强有力的协作，控制序列将在一个新颖的离子陷阱中开发和测试，其参数可以在宽阔的范围内变化。调整量子与运动之间相互作用的强度（羔羊 - dicke参数）和热效应强度的能力将使我们能够以理想的方式确定处理每种不完美的控制策略。大多数当前的实验都是在量子和运动之间的相互作用较弱的，但我们旨在实现与运动强烈相互作用的量子位之间的逻辑操作。强烈相互作用带来的操纵速度提高会增加可以在有限的消耗时间施加的限制内实施的逻辑操作数量，因此将有助于我们从原则证明实验转变为实际应用。我们工作的直接目标是我们的工作来改进量子计算的量子，但我们将对量子进行量子的控制，而我们可以直接进行量子的控制，而是开发了任何类型的控制狂。由于量子位之间的强烈相互作用对快速信息传输是有益的，但是对于在任何量子系统中实施准确的操作方面都具有挑战性，因此有望开发的控制技术在量子光学和量子电子中的其他系统中找到应用。

项目成果

Characterisation and control of trapped-ion qubit

俘获离子量子位的表征和控制

• 发表时间: 2022
• 作者: Lee Chungsun

Population dynamics in sideband cooling of trapped ions outside the Lamb-Dicke regime

• DOI: 10.1103/physreva.99.013423
• 发表时间: 2018-09
• 期刊: Physical Review A
• 影响因子: 2.9
• 作者: M. Joshi;P. Hrmo;V. Jarlaud;F. Oehl;R. Thompson

Quantum coherence in trapped ions

被捕获离子的量子相干性

• 发表时间: 2022
• 作者: Corfield Oliver

Measurement-based ground state cooling of a trapped ion oscillator

基于测量的俘获离子振荡器基态冷却

• DOI: 10.48550/arxiv.2208.05332
• 发表时间: 2022
• 作者: Lee C

Coherent fluctuation relations: from the abstract to the concrete

• DOI: 10.22331/q-2019-02-25-124
• 发表时间: 2019-02-25
• 期刊: QUANTUM
• 影响因子: 6.4
• 作者: Holmes, Zoe;Weidt, Sebastian;Mintert, Florian
• 通讯作者: Mintert, Florian