A quantum register using collective excitations in a Bose-Einstein condensate

TL;DR

This paper proposes a feasible method to create a quantum register using collective excitations in a Bose-Einstein condensate, enabling high-fidelity operations without the need for atom removal or separate storage bases.

Contribution

It introduces a protocol for coherently loading a spin-dependent optical lattice from a BEC to realize a robust quantum register with simplified control and reduced decoherence.

Findings

High-fidelity single-qubit operations demonstrated

Two-qubit gates between arbitrary pairs feasible

Atom losses have minimal impact on coherence

Abstract

A qubit made up of an ensemble of atoms is attractive due to its resistance to atom losses, and many proposals to realize such a qubit are based on the Rydberg blockade effect. In this work, we instead consider an experimentally feasible protocol to coherently load a spin-dependent optical lattice from a spatially overlapping Bose--Einstein condensate. Identifying each lattice site as a qubit, with an empty or filled site as the qubit basis, we discuss how high-fidelity single-qubit operations, two-qubit gates between arbitrary pairs of qubits, and nondestructive measurements could be performed. In this setup, the effect of atom losses has been mitigated, the atoms never need to be removed from the ground state manifold, and separate storage and computational bases for the qubits are not required, all of which can be significant sources of decoherence in many other types of atomic qubits.