Hybrid Acousto-Optical Charge and Spin Control in Quantum Dots

Optically active semiconductor quantum dots (QDs) are at the forefront of platforms for quantum technologies. They offer extensive tunability of optical properties and cover a wide range of energy scales related to their charge and spin qubits. QDs feature interfaces with light, microwaves, nuclear spins, and mechanical waves, which makes them an excellent component of hybrid systems [1].  However, phonons can only modulate the energy in QDs, and thus cannot induce transitions between charge states, and virtually do not interact with the electron spin degree of freedom. To overcome this, we theoretically propose acousto-optical methods that introduce optically gated acoustic state control to this system for both charge and spin states.

For charge states, our method [2] is a hybrid extension of the novel, originally all-optical swing-up approach, in which the state is prepared by periodically switching between two laser detunings [3]. Additionally, we show that higher-harmonic acoustic driving is also possible, thanks to the parametric character of the control based on phase modulation of the excitonic transition [4]. For spin control, we use a detuned optical coupling to a charged exciton state in the Voigt configuration and acoustic modulation of the detuning [5]. We also extend the acoustic swing-up control scheme to QD spin states, and show that arbitrary rotation can be obtained even faster [6]. In all the cases, we predict high-fidelity operation with a detuned laser and an acoustic mode, where either field can act as the gating field, while the other drives the transition.
Those schemes may pave the way for generating entanglement between an emitter and a quantum acoustic mode, leading to subsequent state transfer via an acoustic bus or the realization of phonon-mediated two-qubit gates.

[1] G. Kurizki, et al., Proc. Natl. Acad. Sci. 112, 3866 (2015).
[2] M. Kuniej, P. Machnikowski, and M. Gawełczyk, npj Quantum Inf. 11, 161 (2025).
[3] T. K. Bracht, et al., PRX Quantum 2, 040354 (2021).
[4] M. Kuniej, P. Machnikowski, and M. Gawełczyk, arXiv:2603.09849 (2026).
[5] M. Kuniej, P. Machnikowski, and M. Gawełczyk, Phys. Rev. Lett. 136 046904 (2026).
[6] M. Kuniej, and M. Gawełczyk, in preparation.