Long distance coupling of resonant exchange qubits

TL;DR

This paper demonstrates that microwave cavities can mediate long-distance interactions between resonant exchange qubits in semiconductor quantum dots, enabling fast two-qubit gates over millimeter scales.

Contribution

It introduces a model for qubit-cavity coupling using Wannier orbitals and shows how this enables universal two-qubit gates over long distances.

Findings

Effective qubit-cavity coupling via dipole transitions identified.

Two-qubit iSWAP-gate achievable within nanoseconds.

Long-distance coupling extends to millimeter scales.

Abstract

We investigate the effectiveness of a microwave cavity as a mediator of interactions between two resonant exchange (RX) qubits in semiconductor quantum dots (QDs) over long distances, limited only by the extension of the cavity. Our interaction model includes the orthonormalized Wannier orbitals constructed from Fock-Darwin states under the assumption of a harmonic QD confinement potential. We calculate the qubit-cavity coupling strength in a Jaynes Cummings Hamiltonian, and find that dipole transitions between two states with an asymmetric charge configuration constitute the relevant RX quoit-cavity coupling mechanism. The effective coupling between two RX qubits in a shared cavity yields a universal two-qubit iSWAP-gate with gate times on the order of nanoseconds over distances on the order of up to a millimeter.