Quantum computation toolbox for decoherence-free qubits using multi-band alkali atoms

TL;DR

This paper presents a new method for creating decoherence-free qubits with ultracold alkali atoms in optical lattices, enhancing coherence and control for quantum computing applications.

Contribution

It introduces a protocol that uses higher motional bands to realize tunable interactions without continuous driving, enabling robust qubit manipulation and entanglement generation.

Findings

Decoherence-free qubits exhibit improved coherence times.

Cross-site superexchange interactions can generate 1D cluster states.

Protocols for experimental realization and measurement are provided.

Abstract

We introduce protocols for designing and manipulating qubits with ultracold alkali atoms in 3D optical lattices. These qubits are formed from two-atom spin superposition states that create a decoherence-free subspace immune to stray magnetic fields, dramatically improving coherence times while still enjoying the single-site addressability and Feshbach resonance control of state-of-the-art alkali atom systems. Our protocol requires no continuous driving or spin-dependent potentials, and instead relies upon the population of a higher motional band to realize naturally tunable in-site exchange and cross-site superexchange interactions. As a proof-of-principle example of their utility for entanglement generation for quantum computation, we show the cross-site superexchange interactions can be used to engineer 1D cluster states. Explicit protocols for experimental preparation and manipulation of the qubits are also discussed, as well as methods for measuring more complex quantities such as out-of-time-ordered correlation functions (OTOCs).