Enhancing quantum exchanges between two oscillators

TL;DR

This paper investigates methods to enhance quantum state exchange between two oscillators via a three-level system, employing Hamiltonian engineering and optimal control to improve fidelity in various coupling regimes.

Contribution

It introduces a control scheme for high-fidelity quantum exchange between oscillators using a three-level system, addressing limitations of static coupling conditions.

Findings

High transition probabilities achieved through Hamiltonian engineering.

Time-dependent control fields improve exchange fidelity.

Optimal control reduces fidelity loss in strong coupling regimes.

Abstract

We explore the extent to which two quantum oscillators can exchange their quantum states efficiently through a three-level system which can be spin levels of colored centers in solids. High transition probabilities are obtained using Hamiltonian engineering and quantum control techniques. Starting from a weak coupling approximation, we derive conditions on the spin-oscillator interaction Hamiltonian that enable a high-fidelity exchange of quanta. We find that these conditions cannot be fulfilled for arbitrary spin-oscillator coupling. To overcome this limitation, we illustrate how a time-dependent control field applied to the three-level system can lead to an effective dynamic that performs the desired exchange of excitation. In the (ultra) strong coupling regime, an important loss of fidelity is induced by the dispersion of the excitation onto many Fock states of the oscillators. We show that this detrimental effect can be substantially reduced by suitable control fields, which are computed with optimal control numerical algorithms.