Digital Control of Superconducting Fluxonium Qubits

未来几年超导量子计算机发展面临的两个主要挑战将是(i)有限的相干时间和（ii）可扩展性。本博士旨在结合两种最先进的技术来实现一种架构，以减轻这两个问题。相干时间的第一个问题是利用量子比特（量子比特）解决的。这些量子比特提供的相干时间比目前主导行业的超导量子比特长得多。第二个问题是可扩展性，这是超导量子比特的一个问题，因为目前，每个量子比特都需要大量的实验开销来控制、测量和读取量子信息。这不适用于使用数千或数百万量子位的量子计算机。利用数字单通量量子（SFQ）控制超导量子比特，解决了可扩展性问题。SEEQC等公司正在研究的这项技术，为在超导量子比特运行的低温环境中控制和测量量子比特提供了一条有前途的途径。这消除了使用室温电子设备来控制低温量子比特所需的巨大开销。该项目将涉及使用现成的制造技术设计和制造一个氟鎓量子比特。在成功制造后，目标是将该量子比特耦合到SEEQC提供的SFQ控制芯片上，以演示单个量子比特的相干控制。这些技术的成功结合为高相干性和非常可扩展的超导量子计算机提供了基础。

Two of the main challenges facing the development of superconducting quantum computers in the coming years will be (i) their limited coherence time and (ii) their scalability. This PhD aims to combine two state-of-the-art technologies to realise an architecture that mitigates both of these problems. The first problem of coherence time is addressed by utilising the fluxonium qubit (quantum bit). These qubits have been shown to provide much longer coherence times than the superconducting qubits that currently dominate the industry. The second issue, scalability, is a problem for superconducting qubits because, currently, each qubit requires significant experimental overhead to control, measure and readout the quantum information. This cannot be applied to the quantum computers that utilise thousands or millions of qubits. The problem of scalability is addressed by utilising digital single flux quantum (SFQ) control of superconducting qubits. This technology, being worked on by companies such as SEEQC, provides a promising path to control and measure qubits in the cryogenic environment in which superconducting qubits operate. This removes the significant overhead needed to use room temperature electronics to control cryogenic qubits. The project will involve the design and fabrication of a fluxonium qubit using readily available fabrication techniques. Upon successful fabrication, the aim is to couple this fluxonium qubit to an SFQ control chip provided by SEEQC to demonstrate the coherent control of a single fluxonium qubit. The successful combination of these technologies provides the building blocks for a high coherence and very scalable superconducting quantum computer.