Quantum Gates, Algorithms, and Error Correction with a Neutral Atom Qubit Array

量子计算由于其解决经典计算机上难以解决的实际问题的潜力而引起了人们的极大兴趣。应用领域包括密码学、数据库搜索、模式分类、求解耦合方程的大型系统以及新功能材料或化合物的设计。量子计算机是由量子比特或量子比特构建的，量子比特存储使用量子逻辑门处理的量子信息。该项目将继续使用编码在单个原子内部状态中的量子位来开发量子计算。虽然目前的技术水平涉及10-20个量子比特的实验，但人们认为，要实现量子计算的前景，需要具有数千个量子比特的计算机。在这方面，在这个项目中开发的基于原子的方法是特别有吸引力的，因为大量的中性原子可以被保持和控制在非常接近的位置，而不会相互干扰。该项目旨在推进几个关键性能指标的最新发展：量子位长时间保持量子状态的能力，逻辑门操作和量子位测量的保真度，以及可以在单个系统中准备的量子位数量。这些进展将被用来演示数据库搜索的量子算法。该项目将通过培训学生和博士后研究人员，促进科学工作者队伍的发展。培训将是跨学科的，借鉴原子和激光物理学，电子和基于计算机的控制系统以及量子信息理论的方法和思想。研究成果将纳入大学教学课程。实验方法将使用一个二维的铯和铷原子阵列，这些原子被困在由光定义的势威尔斯阱中。潜在的威尔斯将通过组合几种不同频率的激光来制备，以保护存储的量子信息免受退相干。一个可移动的光镊系统将被实现，以安排被困原子100%占用的阵列与多达50个量子位网站。量子逻辑门将通过激光脉冲将原子激发到里德伯态来产生纠缠。具有成形时间轮廓的绝热脉冲将用于提高纠缠操作的保真度。原子状态将使用两种物质的方法测量，而不会与其他量子比特发生串扰或丢失原子，其中一种物质（铯）将用于存储器和量子逻辑，第二种物质（铷）将用于测量。要测量的量子态将使用种间里德堡门从铯原子转移到铷原子。 然后将利用这些功能来演示多量子位量子算法，该算法为数据库搜索提供二次加速。该团队还将实施量子纠错，以保护量子比特免受位翻转或相位翻转错误的影响。

Quantum computing is attracting great interest due to its potential for solving practical problems that are intractable on classical computers. Areas of application include cryptography, database searching, pattern classification, solving large systems of coupled equations, and design of new functional materials or chemical compounds. A quantum computer is built from quantum bits, or qubits, that store quantum information which is processed using quantum logic gates. This project will continue the development of quantum computing using qubits encoded in the internal states of individual atoms. While the current state of the art involves experiments with 10-20 qubits, it is believed that computers with many thousands of qubits will be needed to realize the promise of quantum computation. In this respect the atom based approach being developed in this project is particularly attractive since a large number of neutral atoms can be held and controlled in close proximity without undesired interference with each other. The project seeks to advance the state of the art of several key performance metrics: the ability of qubits to preserve their quantum states for a long time, the fidelity of logic gate operations and qubit measurements, and the number of qubits that can be prepared in a single system. These advances will then be used to demonstrate a quantum algorithm for database searching. The project will contribute to scientific workforce development through training of students and postdoctoral researchers. The training will be interdisciplinary, drawing on methods and ideas from atomic and laser physics, electronic and computer based control systems, and quantum information theory. Research results will be incorporated into the University teaching curriculum. The experimental approach will use a two-dimensional array of cesium and rubidium atoms trapped in potential wells defined by light. The potential wells will be prepared by combining laser light of several different frequencies in a way that protects stored quantum information from decoherence. A movable optical tweezer system will be implemented to arrange trapped atoms for 100% occupancy of an array with up to 50 qubit sites. Quantum logic gates to create entanglement will be performed by exciting atoms to Rydberg states with laser pulses. Adiabatic pulses with shaped temporal profiles will be used to improve the fidelity of the entangling operations. Atomic states will be measured without crosstalk to other qubits or loss of atoms using a two-species approach whereby one species (cesium) will be used for memory and quantum logic, and a second species (rubidium) will be used for measurements. The quantum states to be measured will be transferred from cesium to rubidium atoms using an interspecies Rydberg gate. These capabilities will then be leveraged to demonstrate a multi-qubit quantum algorithm that provides quadratic speedup for database searching. The team will also implement quantum error correction to protect qubits against bit flip or phase flip errors.