Developing a platform for linear mechanical quantum computing

TL;DR

This paper introduces a solid-state platform for linear mechanical quantum computing by developing a phononic beamsplitter and demonstrating two-phonon interference, enabling quantum gates with phonons in superconducting systems.

Contribution

The paper reports the first realization of a phononic beamsplitter and two-phonon interference in a superconducting system, advancing the development of linear mechanical quantum computing.

Findings

Successful demonstration of a phononic beamsplitter.

Observation of two-phonon interference.

Complete toolbox for linear mechanical quantum computing.

Abstract

Linear optical quantum computing provides a desirable approach to quantum computing, with a short list of required elements. The similarity between photons and phonons points to the interesting potential for linear mechanical quantum computing (LMQC), using phonons in place of photons. While single-phonon sources and detectors have been demonstrated, a phononic beamsplitter element remains an outstanding requirement. Here we demonstrate such an element, using two superconducting qubits to fully characterize a beamsplitter with single phonons. We further use the beamsplitter to demonstrate two-phonon interference, a requirement for two-qubit gates, completing the toolbox needed for LMQC. This advance brings linear quantum computing to a fully solid-state system, along with straightforward conversion between itinerant phonons and superconducting qubits.