Scalable implementation of hybrid spin qubits in CMOS-compatible devices

量子计算机将解决即使是经典超级计算机也不可能在合理时间内解决的问题。理论研究表明，与经典计算机相比，在密码学、优化和模拟等应用方面，量子加速是意料之中的。然而，要实现这种量子加速，需要大量可访问的极高保真度的量子比特。目前的量子技术提供了几十个量子比特，多量子比特门的保真度勉强令人满意，但它仍然面临着量子比特以及外围控制电路的规模扩大问题。研究人员已经证明了由硅(Si)衬底中杂质施主或量子点的自旋态构成的量子比特具有创纪录的相干时间。与此同时，硅基量子比特可能会受益于标准的工业互补金属氧化物半导体(CMOS)工艺而扩大规模。在过去的几十年里，cmos工艺一直在发展，最先进的工艺可以在一个厘米级的芯片内生产数十亿个晶体管。因此，基于其强大的量子信息存储能力和利用成熟制造工艺的可能性，硅自旋量子比特是非常有前途的量子计算候选者。这个项目将研究一种可能的基于硅纳米线场效应晶体管(SiNW-FET)的自旋量子比特实现。量子点，或可能位于FET通道内的施主，将被用作量子比特，并将研究使用全局控制来改进缩放的策略。将评估使用浮动门的量子比特耦合，并优化使用反射法实现高保真自旋读出的技术。

A quantum computer will solve problems that are impossible even for classical supercomputers to solve in reasonable time. Theoretical studies have indicated an expected "quantum speed-up" over classical computers in applications such as cryptography, optimization and simulation. However, to achieved this quantum speed-up requires large number of accessible qubits with extremely high fidelity. Current quantum technology offered few tens of qubits with barely satisfactory multi-qubit gate fidelity, and still it faces scaling up issues both in qubits as well as in peripheral control circuitry. Researchers have demonstrated qubits constructed from the spin states of impurity donors or quantum dots in silicon(Si) substrates with record-high coherence times. Meanwhile, Si-based qubits could potentially scale up benefiting from the standard industrial complementary metal oxide semiconductor (CMOS) processes. CMOS processes have been developing for the past few decades and state-of-art process can produce billions of transistors within a cm-scale chip. Therefore, silicon spin qubits are very promising candidates for quantum computing based on its robust storage of quantum information and possibility to leverage mature manufacturing processes. This project will investigate a possible spin qubit implementation based on silicon Nanowire Field Effect Transistors (Si NW-FETs). Quantum dots, or potentially donors located within the FET channel, will be used as the qubits, and strategies for using global control to improve scaling will be investigated. Qubit coupling using floating gates will be evaluated, and techniques to achieve high-fidelity spin read-out using reflectometry will be optimised.