BioComp: Collaborative Research: Is Resilient Quantum Computing in Solid State Systems Possible?

这笔拨款支持与在固态设备中实现量子计算相关的基本问题的理论研究。自从发现某些任务可以通过基于量子力学的算法以极高的效率完成以来，人们一直在努力寻找合适的量子硬件。尽管一些已提出的实现方案，如基于核磁共振和原子捕获的方案，已经通过了原理证明，少量子比特阶段，但实现可靠的多量子比特量子计算机的途径仍然没有定义。在这个方案中，我们研究了使用固态量子比特(量子比特)进行弹性计算的物理限制，例如组装量子点和超导结。虽然固态量子比特从制造的角度看起来很容易扩展，但与其他实现方式相比，它们也呈现出高的消相干速率。一个主要的担忧是，如此强烈的退相干可能会导致错误发生的速度太大，以至于无法控制。然而，与其他核、原子和光学量子比特不同的是，固态量子设备与环境的相互作用可以引入强烈的记忆效应。因此，在多量子比特系统的运行过程中，可能会出现时间关联。目前的量子纠错码不是针对这种情况而设计的，它可能会使基于这些码的效率的任何固态量子比特的错误阈值估计无效。我们将全面地探讨这些问题。从研究单量子比特系统和双量子比特系统的消相干机制出发，我们将研究在各种现实条件下存在关联噪声的多量子比特系统的模型。我们的结果将有助于建立多量子比特系统运行的新策略。它们还将让我们了解纠错码需要满足哪些限制，以便在大规模固态实现中实现容错量子计算。为了实现我们的目标，我们组建了一支在纳米物理和计算机科学方面具有专业知识的研究团队。我们项目的最终结果将是更好地理解真正的固态量子计算机的行为方式。

This grant supports theoretical research on fundamental issues relatedto the implementation of quantum computation in solid-statedevices. Since the discovery that certain tasks could be performedwith great efficiency by algorithms based on quantum mechanics, anintense effort has been made to find suitable quantumhardware. Although several proposed implementations, such as thosebased on nuclear magnetic resonance and atomic trapping, have passedthe proof-of-principle, few-qubit phase, the path to achieving areliable multi-qubit quantum computer is still undefined.In this proposal we investigate the physical limitations to resilientcomputation with solid-state quantum bits (qubits), such assemiconductor quantum dots and superconductor junctions. Whilesolid-state qubits seem easily scalable from the fabricationviewpoint, they also present high decoherence rates as compared toother implementations. One major concern is that such strong decoherence may lead to errors occurring at a rate too large to be controlled.However, differently from other nuclear, atomic, and optical qubits, the interaction of solid-state quantum devices with the environment can introduce strong memory effects. As a result, temporal correlations may appear during the operation of multi-qubit systems. Current quantum error correction codes are not designed to cope with this situation, which may then invalidate any error threshold estimate for solid-state qubits based on the efficiency of those codes.We will explore these issues in a comprehensive way. Starting from athorough study of the mechanisms of decoherence in single- anddouble-qubit systems, we will study a model of multi-qubit systems inthe presence of correlated noise in a variety of realisticconditions. Our results will help set up new strategies for theoperation of multi-qubit systems. They will also let us understandwhat are the constraints that error correction codes will need tosatisfy in order to achieve fault-tolerant quantum computation inlarge-scale solid state implementations. To achieve our goals, we haveput together a team of researchers with expertise in nanoscale physics and computer science. The final outcome of our project will be a muchbetter understanding of how a real solid-state quantum computer wouldbehave.