Hybrid 2D/3D superconducting circuits for quantum computing

Lead Research Organisation: University of Oxford
Department Name: Oxford Physics

Abstract

Superconducting circuits have emerged as a strong candidate for building working universal quantum computers, but a range of difficult challenges still remain to be solved before this dream is finally realized. One significant issue that emerges for larger scale circuits is signal crosstalk between different control signals and circuit elements, and interaction with unwanted spurious 3D modes. This occurs due to the fact that the size of the 3D enclosure around the 2D circuit becomes of order, or larger than, the wavelength of light at the frequency of operation of the circuit. This makes it easier for microwaves to propagate around the circuit, and leads to the existence of new resonant modes. We need to develop smart 'quantum microwave engineering' to circumvent these problems.

This project will build on the recent development of a new architecture for quantum computing in our group based on coaxial circuit elements and out-of-plane control. We have demonstrated the architecture at the one-qubit level [1] and have recently scaled this to two qubits, including full two-qubit quantum logic at close to state-of-the-art (99.9% and 98% fidelities for one and two-qubit gate fidelities respectively). The CASE industrial partner for the project, the spin-out company Oxford Quantum Circuits, has formed to develop this architecture for quantum computing applications, and is tightly connected to the group.

The project will initially involve design, simulation, fabrication and measurement of circuit/enclosure combinations that include solutions to these crosstalk and spurious mode issues, and will move on then to explore the utilization of deliberately engineered 3D features or modes that add new functionality to large scale circuits, like long distance couplings and signal multiplexing and filtering.

EPSRC Priority area: 21st century products: Quantum technologies: Quantum computers. This project addresses a current and very central challenge for quantum computing with superconducting circuits - that of crosstalk and 3D-mode presence in large scale circuits. Prospects for practical large scale quantum computing will be dramatically improved if we are successful.

[1] Rahamim et al., APL 110, 222602 (2017)

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/R513295/1 01/10/2018 30/09/2023
2426053 Studentship EP/R513295/1 01/10/2018 31/03/2022 James Fox Wills