Quantum Error Correction in a dual-species Rydberg array (QuERy)

量子计算提供了一个新的范例，其中使用在量子力学定律下运行的系统来解决复杂的问题，例如在量子化学中用于增强药物设计或相关介质的建模，用于设计目前超出现代数字计算机能力的航空航天和工程新材料。量子硬件还可以为计算昂贵的问题提供显着的加速，从与物流相关的经典优化（例如旅行推销员类型的问题）到因子分解。然而，利用量子计算的优势来解决这些真实的世界问题的主要障碍是与构建能够提供足够数量的高质量、低噪声量子比特（qu-bits）的系统相关的技术挑战。最近的进展已经看到了许多不同技术的发展来解决这一挑战，包括超导量子比特和捕获离子，然而，单独捕获的原子的可重构阵列已经成为一种高度竞争性的方法，其能够在不损失性能的情况下缩放到大量相同的量子位。这些目前只有几百个量子比特的系统为探索量子计算的早期好处提供了机会，但受到噪声和错误的影响，这限制了它们的性能和解决有用问题的能力。为了克服这种限制，有必要执行纠错以修复错误，否则会破坏计算机输出。在数字硬件中，这是通过对存储在逻辑寄存器中的信息进行测量来实现的。对于量子计算机来说，这很难实现，因为信息被编码在脆弱的叠加态中，当直接测量时会导致信息丢失。解决这个问题的一个途径是使用多个量子比特来执行量子纠错，以通过利用具有特别选择的对称性的拓扑保护状态来编码单个逻辑量子比特。为了在不擦除量子态的情况下检查错误，使用额外的量子位（称为ancillas）来执行对称性的局部测量，之后可以使用标准门协议来纠正错误。虽然已经提出了一系列用于执行量子纠错的编码方案，但到目前为止，这仅在超导体和离子的少数量子比特系统上实现，并且由于仅使用单个原子物种时串扰的挑战，尚未在更具可扩展性的中性原子平台上进行演示。在QuERy中，我们将为中性原子量子计算开发一个新的双物种平台，以直接解决将量子硬件从100个量子比特扩展到数百万个量子比特的主要障碍，即通过在低温环境中集成来延长原子阵列捕获寿命，以抑制由于原子丢失而导致的错误，并通过执行无串扰的能力来演示量子纠错，通过使用一个物种编码信息和第二个物种执行本地辅助测量的状态选择性本地测量。这项研究将为中性原子量子计算提供新的模式，包括通过随机测量进行验证和基准测试，并开发能够利用拓扑编码来实现横向门操作的算法。这些结果对于实现大规模容错量子计算机至关重要，这些计算机需要利用量子计算在学术界和工业界的变革性优势，包括材料设计，物流和量子化学等应用。

Quantum computing provides a new paradigm in which to use systems operating under the laws of quantum mechanics to solve complex problems such as in quantum chemistry for enhanced drug design or modelling of correlated media for designing new materials for aerospace and engineering which are currently beyond the capability of modern digital computers. Quantum hardware can also provide a dramatic speed-up of computationally expensive problems ranging from classical optimisation relevant to logistics (e.g. travelling salesman type problems) to factorisation. The major barriers to exploiting the advantages of quantum computing for these real world problems however are the technological challenges associated with building a system able to provide a sufficient number of high quality, low noise quantum-bits (qu-bits).Recent progress has seen the development of a number of different technologies to address this challenge, including superconducting qubits and trapped ions, however reconfigurable arrays of individually trapped atoms have emerged as a highly competitive approach able to scale to large numbers of identical qubits without loss of performance. These current systems with a few hundred qubits offer opportunities to explore early benefits of quantum computing, but suffer from noise and errors which place a limit on the performance and their ability to address useful problems.To overcome this limitation, it is necessary to perform error correction to fix the errors that otherwise corrupt the computer output. In digital hardware this is achieved by performing measurements on the information stored in logical registers. For a quantum computer this is much harder to implement, as the information is encoded in fragile superposition states which when measured directly results in a loss of information. One route to address this problem is to perform quantum error correction using a number of qubits to encode a single logical qubit by exploiting topologically protected states with specially chosen symmetry properties. To check for errors without erasing the quantum states, additional qubits (known as ancillas) are used to perform local measurements of the symmetries, after which errors can be corrected using standard gate protocols. Whilst a range of encoding schemes have been proposed for performing quantum error correction, this has so far only been implemented on few qubit systems of superconductors and ions and has yet to be demonstrated on the more scalable neutral atom platform due to challenges with cross talk when a only a single atomic species is used. In QuERy we will develop a new dual-species platform for neutral atom quantum computing to directly address major barriers to scaling up quantum hardware from 100s to millions of qubits, namely extending atom array trapping lifetimes through integration in a cryogenic environment to suppress errors due to atom loss, and demonstrating quantum error correction through the ability to perform cross-talk free, state-selective local measurements by using one species for encoding information and a second species to perform local ancilla measurements.This research will provide new modalities for neutral atom quantum computing, including enabling verification and benchmarking through randomised measurements, and develop algorithms able to exploit topological encodings to implement transverse gate operations. These results are crucial for the realisation of large-scale, fault-tolerant quantum computers as required to exploit the transformative benefits of quantum computing across both academia and industry, including applications such as material design, logistics and quantum chemistry for drug discovery.