Dipolar Exchange Quantum Logic Gate with Polar Molecules

TL;DR

This paper proposes a high-fidelity two-qubit quantum logic gate using dipolar exchange interactions between ultracold polar molecules, enabling scalable quantum computing with minimal external field sensitivity.

Contribution

It introduces a novel switchable dipolar exchange interaction-based two-qubit gate utilizing full molecular Hamiltonian and nuclear spin states, achieving over 99.99% fidelity.

Findings

Potential fidelity above 99.99% in ideal conditions

Gate operation is insensitive to external magnetic and electric fields

Scalable quantum system using purely optical methods

Abstract

We propose a two-qubit gate based on dipolar exchange interactions between individually addressable ultracold polar molecules in an array of optical dipole traps. Our proposal treats the full Hamiltonian of the $^1\Sigma^+$ molecule NaCs, utilizing a pair of nuclear spin states as storage qubits. A third rotationally excited state with rotation-hyperfine coupling enables switchable dipolar exchange interactions between two molecules to generate an iSWAP gate. All three states are insensitive to external magnetic and electric fields. Impacts on gate fidelity due to coupling to other molecular states, imperfect ground-state cooling, blackbody radiation and vacuum spontaneous emission are small, leading to potential fidelity above $99.99~\%$ in a coherent quantum system that can be scaled by purely optical means.