A mechanical qubit

TL;DR

This paper demonstrates a solid-state mechanical system that operates as a single-phonon nonlinear quantum bit, enabling quantum control and readout at the single-phonon level, advancing quantum acoustics applications.

Contribution

It introduces a mechanical qubit based on single-phonon nonlinearities with anharmonicity surpassing decoherence, enabling quantum gate operations in a solid-state system.

Findings

Achieved single-phonon anharmonicity exceeding decoherence rate by 6.8 times

Demonstrated initialization, readout, and quantum gates for the mechanical qubit

Enhanced quantum acoustics platform for quantum information processing

Abstract

Strong nonlinear interactions between quantized excitations are an important resource for quantum technologies based on bosonic oscillator modes. However, most electromagnetic and mechanical nonlinearities arising from intrinsic material properties are far too weak compared to dissipation in the system to allow for nonlinear effects to be observed on the single-quantum level. To overcome this limitation, electromagnetic resonators in both the optical and microwave frequency regimes have been coupled to other strongly nonlinear quantum systems such as atoms and superconducting qubits, allowing for the demonstration of effects such as photon blockade and coherent quantum protocols using the Kerr effect. Here, we demonstrate the realization of the single-phonon nonlinear regime in a solid-state mechanical system. The single-phonon anharmonicity in our system exceeds the decoherence rate by a factor of 6.8, allowing us to use the lowest two energy levels of the resonator as a mechanical qubit, for which we show initialization, readout, and a complete set of direct single qubit gates. Our work adds another unique capability to a powerful quantum acoustics platform for quantum simulations, sensing, and information processing.