Phonon-mediated quantum state transfer and remote qubit entanglement

Understand

Phonons, and in particular surface acoustic wave phonons, have been proposed as a means to coherently couple distant solid-state quantum systems.

• Recent experiments have shown that superconducting qubits can control and detect individual phonons in a resonant structure, enabling the coherent generation and measurement of complex stationary phonon states.
• Here, we report the deterministic emission and capture of itinerant surface acoustic wave phonons, enabling the quantum entanglement of two superconducting qubits.
• Using a 2 mm-long acoustic quantum communication channel, equivalent to a 500 ns delay line, we demonstrate the emission and re-capture of a phonon by one qubit; quantum state transfer between two qubits with a 67\% efficiency; and, by partial transfer of a phonon between two qubits, generation of an entangled Bell pair with a fidelity of $\mathcal{F}_B = 84 \pm 1$ %