Prospects for Quantum Computing with an Array of Ultracold Polar Paramagnetic Molecules

TL;DR

This paper explores the potential of using arrays of ultracold polar paramagnetic molecules for quantum computing, demonstrating how to control entanglement and implement quantum gates with external fields.

Contribution

It introduces a novel approach using polar $^2\Sigma$ molecules with Bell states, proposing schemes for optically controlled CNOT gates and analyzing their feasibility.

Findings

Entanglement can be tuned with electric and magnetic fields.

Proposed schemes for CNOT gate implementation.

Feasibility affected by spectral broadening and field inhomogeneity.

Abstract

Arrays of trapped ultracold molecules represent a promising platform for implementing a universal quantum computer. DeMille has detailed a prototype design based on Stark states of polar $^1\Sigma$ molecules as qubits. Herein, we consider an array of polar $^2\Sigma$ molecules which are, in addition, inherently paramagnetic and whose Hund's case (b) free-rotor states are Bell states. We show that by subjecting the array to combinations of concurrent homogeneous and inhomogeneous electric and magnetic fields, the entanglement of the array's Stark and Zeeman states can be tuned and the qubit sites addressed. Two schemes for implementing an optically controlled CNOT gate are proposed and their feasibility discussed in the face of the broadening of spectral lines due to dipole-dipole coupling and the inhomogeneity of the electric and magnetic fields.