Long-range two-hybrid-qubit gates mediated by a microwave cavity with red sidebands

TL;DR

This paper explores schemes for long-range two-qubit gates between quantum-dot hybrid qubits mediated by a microwave cavity, demonstrating high fidelities and leveraging unique sweet spots for strong coupling.

Contribution

It introduces off-resonant red-sideband-mediated gates exploiting quantum dot hybrid qubit properties, achieving high fidelities and addressing long-distance gate challenges.

Findings

Fidelities >95% with realistic parameters.

Identification of sweet spots with strong charge dipole moments.

Potential for fidelities >99% with improvements.

Abstract

Implementing two-qubit gates via strong coupling between quantum-dot qubits and a superconducting microwave cavity requires achieving coupling rates that are much faster than decoherence rates. Typically, this involves tuning the qubit either to a sweet spot, where it is relatively insensitive to charge noise, or to a point where it is resonant with the microwave cavity. Unfortunately, such operating points seldom coincide. Here, we theoretically investigate several schemes for performing gates between two quantum-dot hybrid qubits, mediated by a microwave cavity. The rich physics of the quantum dot hybrid qubit gives rise to two types of sweet spots, which can occur at operating points with strong charge dipole moments. Such strong interactions provide new opportunities for off-resonant gating, thereby removing one of the main obstacles for long-distance two-qubit gates. Our results suggest that the numerous tuning knobs of quantum dot hybrid qubits make them good candidates for strong coupling. In particular, we show that off-resonant red-sideband-mediated two-qubit gates can exhibit fidelities $>$95\% for realistic operating parameters, and we describe improvements that could potentially yield gate fidelities $>$99\%.