Materials challenges and opportunities for quantum computing hardware

Abstract

Quantum computing hardware technologies have advanced during the past two decades, with the goal of building systems that can solve problems that are intractable on classical computers. The ability to realize large-scale systems depends on major advances in materials science, materials engineering, and new fabrication techniques. We identify key materials challenges that currently limit progress in five quantum computing hardware platforms, propose how to tackle these problems, and discuss some new areas for exploration. Addressing these materials challenges will require scientists and engineers to work together to create new, interdisciplinary approaches beyond the current boundaries of the quantum computing field.

Ternary Metal Oxide Substrates for Superconducting Circuits

“…As current device performance is largely limited by material issues, it is imperative to explore broader classes of materials to gauge their suitability for quantum devices. 1,2 This approach has recently been highly successful in the case of superconducting materials, where tantalum was shown to dramatically increase coherence times. 5 As noted in the introduction, while new substrate materials have been trialled, these efforts have not focused on surface preparation putting these efforts behind established methods for working with silicon and sapphire.…”

“…Silicon and sapphire are the current workhorse substrates for superconducting quantum devices. 1,2 As superconducting devices have advanced, material engineering has played a critical role in increasing resonator quality factor and qubit coherence time, with notable increases due to the removal of disorder at device interfaces. 3,4 In the case of resonators, state-of-theart devices on silicon and sapphire substrates can have quality factors on the order of 10 6 in the single photon regime.…”

“…However, the range of potentially useful (and widely available) substrates has only been explored in a limited fashion. 1 The focus on new substrate materials is motivated by past success in substrate engineering and more recent work on utilizing less common superconducting materials such as tantalum. 5 Exploring new materials has the potential to shed new light on the microscopic origins of decoherence, ultimately leading to improved device function.…”

“…5 Exploring new materials has the potential to shed new light on the microscopic origins of decoherence, ultimately leading to improved device function. 1 Currently, material and interfacial losses are the most prominent factors hindering the development of a useful quantum computer. 2,6 Alternative substrate materials for superconducting devices have been most investigated in relation to hybrid quantum devices, where superconducting elements are coupled to optical, mechanical, or spin degrees of freedom.…”

Variational Quantum Optimization with Multi-Basis Encodings

“…• By doubling the amount of optimization features encoded into a single qubit, MBEs halve the number of qubits required for a given optimization task, a valuable asset for a developing field which has invested millions of dollars and spent multiple decades to achieve ∼ 50-qubit registers and where additional coherence limitations emerge at scale [35]. Moreover, by utilizing single-qubit measurements, these algorithms yield up to a quadratic reduction in runtime.…”