Protecting collective qubits from non-Markovian dephasing

TL;DR

This paper introduces a novel approach to model and mitigate non-Markovian dephasing in collectively-encoded qubits, demonstrating enhanced coherence times through strong driving and non-Markovian effects in experiments with Rydberg superatoms.

Contribution

It presents a new phase space description for non-Markovian dephasing and shows how to protect collective qubits from decoherence using strong driving and non-Markovianity.

Findings

Accurate simulation of non-Markovian dephasing dynamics.

Protection of qubits extends coherence beyond typical dephasing times.

Experimental validation with Rydberg superatoms demonstrates increased coherence.

Abstract

Collectively-encoded qubits, involving ensembles of atomic or solid-state emitters, present many practical advantages for quantum technologies. However, they suffer from uncontrolled inhomogeneous dephasing which couples them to a quasi-continuum of dark states. In most cases, this process cannot be encompassed in a standard master equation with time-independent coefficients, making its description either tedious or inaccurate. We show that it can be understood as a displacement in time-frequency phase space and accurately included in resource-efficient numerical simulations of the qubit's dynamics. This description unveils a regime where the qubit becomes protected from dephasing through a combination of strong driving and non-Markovianity. We experimentally investigate this regime using a Rydberg superatom and extend its coherent dynamics beyond the inhomogeneous-dephasing characteristic time by an order of magnitude.