Coherent spin-qubit photon coupling

TL;DR

This paper demonstrates strong coupling between microwave photons and a three-electron spin-qubit in a quantum dot, advancing the potential for long-distance quantum information transfer using photons.

Contribution

It reports the first strong spin-photon coupling in a GaAs triple quantum dot with tunable decoherence, measured via vacuum Rabi splitting.

Findings

Coupling strength of approximately 31 MHz achieved.

Decoherence rate tunable down to about 10 MHz.

Direct measurement of coupling dependence on electric dipole moment.

Abstract

Electron spins hold great promise for quantum computation due to their long coherence times. An approach to realize interactions between distant spin-qubits is to use photons as carriers of quantum information. We demonstrate strong coupling between single microwave photons in a NbTiN high impedance cavity and a three-electron spin-qubit in a GaAs triple quantum dot. We resolve the vacuum Rabi mode splitting with a coupling strength of $g/2\pi\simeq31$ MHz and a qubit decoherence of $\gamma_2/2\pi\simeq 20$ MHz. We can tune the decoherence electrostatically and obtain a minimal $\gamma_2/2\pi\simeq 10$ MHz for $g/2\pi\simeq 23$ MHz. The dependence of the qubit-photon coupling strength on the tunable electric dipole moment of the qubit is measured directly using the ac Stark effect. Our demonstration of strong spin-photon interaction is an important step towards coherent long-distance coupling of spin-qubits.