Quantum computing, simulation and error correction in a dual species array

该项目旨在开发一个用于中性原子量子计算和模拟的双物种平台，为实现未来扩展到100个量子比特以上所必需的主动量子纠错提供一条途径。由于能够独立控制物种间和物种内的相互作用，该硬件将同时为模拟计算和模拟提供多功能平台，为执行复杂多体物理学研究提供途径，并增加可以使用中性原子硬件解决的现实世界优化问题的多样性。在过去十年中，中性原子已经成为用于量子信息处理的最有前途的平台之一，其相对于竞争技术的主要优势在于能够按比例缩放到执行实际量子计算所需的大量相同量子位。到目前为止，几个实验已经证明了具有> 256个量子位的量子位阵列的捕获。为了耦合中性原子量子比特，使用高度激发的里德伯态，其具有极大的电偶极矩，从而产生强且可控的相互作用。这些可以被用来执行高保真多量子位门，其中对于两个量子位证明了F>0.95，并且对于多量子位门证明了F>0.995的本征量子度，或者用于执行研究材料或解决优化问题所需的可控自旋模型的量子模拟。当前的许多挑战限制了基于单个原子种类的硬件的更大阵列尺寸的缩放。第一个原因是由于与背景原子的碰撞将原子从陷阱中弹出而导致的有限真空寿命。对于室温操作，这对于1个原子通常是10秒，但对于1000个原子阵列仅意味着10毫秒。这可以通过在低至4K的低温下操作来解决，其中冷表面导致寿命显著增加> 6000秒，这意味着即使对于1000个原子也恢复时间> 6s。下一个问题在于中性原子量子位的长读出时间，通常需要10-50 ms来读出量子位状态。对于单个物种，串扰和散射光意味着读出对整个阵列具有破坏性，该项目将通过在4K低温恒温器内建立双物种中性原子阵列以获得增强的真空寿命并提供对一个物种进行测量的能力来解决这两个挑战（读出量子位），同时保留其他物种（逻辑量子位）上的相干量子态。这提供了一种克服本地寻址和串扰挑战的途径，因为这两种物质在相隔10 nm的光波长下工作。

This project seeks to develop a dual-species platform for quantum computing and simulation with neutral atoms, providing a route to implementing active quantum error correction essential for future scaling beyond 100 qubits. This hardware will simultaneously provide a versatile platform for analogue computing and simulation due to the ability to independently control inter- and intra-species interactions, providing a route to performing studies of complex many-body physics as well as increasing the diversity of real-world optimisation problems that can be tackled using neutral atom hardware.Over the last decade, neutral atoms have emerged as one of the most promising platforms for quantum information processing, with a major advantage over competing technologies arising from the ability to scale to large numbers of identical qubits as required for performing practical quantum computing. To date, several experiments have demonstrated trapping of qubit arrays with > 256 qubits. To couple neutral atom qubits, highly excited Rydberg states are used which have extremely large electric dipole moments giving rise to strong and controllable interactions. These can be exploited to perform high fidelity multi-qubit gates, with F>0.95 demonstrated for two qubits and intrinsic fidelities of F>0.995 for multi-qubit gates, or for performing quantum simulation of controllable spin models as required for studying materials or solving optimisation problems.Whilst there has been significant experimental progress, a number of challenges currently limit scaling to larger array sizes for hardware based on a single atomic species. The first arises from finite vacuum lifetime due to collisions with background atoms ejecting atoms from the trap. For room temperature operation, this is typically 10s for 1 atom but means only 10ms for a 1000 atom array. This can be solved by moving to operation at cryogenic temperatures down to 4 K where the cold surfaces cause significant increase in lifetime upwards of > 6000 seconds meaning recovery of times > 6s even for 1000 atoms. The next issue lies in the long readout time for neutral atom qubits, typically requiring 10-50 ms to readout qubit states. With a single species, the cross-talk and scattered light mean readout is destructive across the whole array, with no clear pathway to performing local measurements required for error correction to reach fault tolerant operation.This project will tackle these two challenges by establishing a dual-species neutral atom array within a 4 K cryostat to obtain enhanced vacuum lifetimes and providing the ability to perform measurement on one species (the readout qubits) whilst retaining coherent quantum states on the other species (the logical qubits). This provides a route to overcome challenges with local addressing and cross talk as the two species operate at optical wavelengths separated by 10s of nm.