Higher-harmonic acoustic driving of quantum-dot optical transitions beyond Rabi-frequency resonance

TL;DR

This paper demonstrates a method to control quantum-dot optical transitions using higher-harmonic acoustic phonons at accessible frequencies, enabling advanced on-chip quantum technologies with high fidelity.

Contribution

It introduces a novel higher-harmonic-assisted process for quantum-dot control, overcoming previous frequency limitations and enabling multi-phonon resonances for quantum state manipulation.

Findings

Faithful quantum state preparation at 42 GHz acoustic frequency

High state-preparation fidelities comparable to existing schemes

Potential for multi-phonon entanglement and quantum state transfer

Abstract

Acoustic control and coupling of quantum systems via phonons can enable miniaturized quantum technology devices for on-chip integration. Optically active quantum dots (QDs) are essential for such platforms, yet they have long lacked direct acoustic transitions between charge states. The recently proposed hybrid acousto-optical swing-up scheme introduces such high-fidelity transitions but has been proposed for sub-THz phonon frequencies, limiting practical implementations. Here, we overcome this limitation by exploiting higher-harmonic-assisted processes arising from strain-induced modulation of the optical transition energy. This parametric modulation of the optically dressed splitting produces multi-phonon-like resonances when a harmonic of the mechanical modulation matches the generalized Rabi frequency. We predict faithful state preparation with an acoustic frequency that is only a fraction of this splitting, specifically 42 GHz for a 0.341 THz splitting, thereby bridging control at accessible acoustic frequencies with the THz energy scales. In doing so, we establish control principles that separate optical energy delivery from coherent acoustic control. We complement numerical simulations with an effective model and a geometric interpretation. Evaluation of phonon-induced decoherence within a non-Markovian framework indicates high state-preparation fidelities, comparable to one-phonon and all-optical schemes. Potential applications extend beyond QD charge state preparation. Since the same interaction structure arises for a quantized acoustic field, our results provide a foundation for multi-phonon processes in QDs coupled to phononic resonators, including QD-phonon entanglement, state transfer, and the optical preparation of nonclassical multi-phonon states in quantized acoustic modes, all essential for future on-chip quantum technologies.