Non-Markovian dynamics of collectively-encoded qubits

• URL: http://arxiv.org/abs/2501.07232v1
• Date: Mon, 13 Jan 2025 11:32:01 GMT
• Title: Non-Markovian dynamics of collectively-encoded qubits
• Authors: Antoine Covolo, Valentin Magro, Mathieu Girard, Sébastien Garcia, Alexei Ourjoumtsev,
• Abstract summary: Collectively-encoded qubits suffer from uncontrolled inhomogeneous dephasing. We show that it can be understood as a displacement in time-frequency phase space. We experimentally investigate this regime using a Rydberg superatom.
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• 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.

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