All-mechanical coherence protection and fast control of a spin qubit

TL;DR

This paper demonstrates a novel all-mechanical method for protecting and controlling a solid-state spin qubit using phononic cavities, enabling ultrafast operations and paving the way for robust quantum phononic networks.

Contribution

It introduces a compatible coherence protection scheme for spin qubits in phononic systems and achieves record-high Rabi frequencies for ultrafast quantum control.

Findings

All-mechanical coherence protection of a spin qubit demonstrated.

Record-high Rabi frequencies of 800 MHz achieved.

Compatibility of coherence protection with phononic cavities confirmed.

Abstract

In a phononic quantum network, quantum information is stored and processed within stationary nodes defined by solid-state spins, and the information is routed between nodes by phonons. The phonon holds distinct advantages over its electromagnetic counterpart the photon, including smaller device footprints, reduced crosstalk, long coherence times at low temperatures, and strong interactions with both solid-state spins and electromagnetic waves. Enhanced interactions between a phononic cavity and a stationary qubit have been demonstrated in multiple platforms including superconducting qubits, spins in silicon carbide and spins in diamond. However, an outstanding issue is the compatibility between the spin's coupling to the resonant phononic cavity and the simultaneous use of pulse sequences to extend the coherence time of the spin by suppressing the low-frequency environmental noise. Here we demonstrate all-mechanical coherence protection of a solid-state spin qubit, where optical initialization, quantum operations, and readout are performed in a dressed basis that is highly immune to low-frequency noise and compatible with a phononic cavities. We additionally show record-high Rabi frequencies reaching 800 MHz, which allows for ultrafast quantum control. Our results establish a first step for high-fidelity, phonon-mediated quantum gates and represent a crucial advance toward robust on-chip quantum phononic networks.