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

该基金支持在固态设备中实现量子计算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高效地执行以来，人们一直在努力寻找合适的量子硬件。虽然一些基于核磁共振和原子俘获的实现方案已经通过了原理验证，但实现可靠的多量子位量子计算机的途径仍然没有确定。在这个方案中，我们研究了使用固态量子位（量子位）（如半导体量子点和超导结）进行量子计算的物理限制。虽然固态量子比特从制造的角度来看似乎很容易扩展，但与其他实现方式相比，它们也具有很高的退相干率。然而，与其他核、原子和光学量子比特不同的是，固态量子器件与环境的相互作用会引入强烈的记忆效应。因此，在多量子位系统的操作期间可能出现时间相关性。目前的量子纠错码并不是为了科普这种情况而设计的，这可能会使基于这些码的效率的固态量子比特的任何错误阈值估计无效。从深入研究单量子比特和双量子比特系统中的退相干机制开始，我们将研究在各种现实条件下存在相关噪声的多量子比特系统模型。我们的研究结果将有助于为多量子比特系统的操作建立新的策略。他们也将让我们了解什么是纠错码需要满足的限制，以实现容错量子计算在大规模的固态实现。为了实现我们的目标，我们组建了一个具有纳米物理学和计算机科学专业知识的研究团队。我们项目的最终成果将是更好地理解真实的固态量子计算机的行为。

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.