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SYCC: Symposium Quantum Computing and Communication: Early Days and New Developments

SYCC 1: Quantum Computing and Communication: Early Days and New Developments

SYCC 1.3: Invited Talk

Tuesday, September 9, 2025, 12:05–12:45, ZHG010

Perspectives on Control and Characterization of Temporally Correlated Nonclassical Noise — •Lorenza Viola — Dartmouth College, Hanover, NH 03755, USA

Accurate characterization and control of realistic open-quantum system dynamics is vital for exploiting the full potential of quantum technologies. Over the past decade, substantial progress has been made in developing qubit-based quantum noise spectroscopy techniques, which have revealed how realistic noise often exhibits strong correlations both in space and time. Still, even in the simplest setting of a single qubit exposed to pure-dephasing noise, understanding the full implications of modeling the environment as a genuinely quantum, as opposed to a classical system, remains surprisingly subtle. I will revisit the use of dynamical decoupling to protect a single-qubit gate in the presence of dephasing noise that is both temporally correlated and nonclassical, and show how the evolution of the quantum bath statistics causes the gate fidelity to depend strongly on the applied control history even if the system-side error propagation is fully removed through perfect reset operations. As a result, the fidelity can saturate at a value substantially lower than the one achievable with no intervening history. Only if decoupling can keep the qubit highly pure over a timescale larger than the noise correlation time, the bath is shown to approximately re-equilibrate to its original statistics and a stable-in-time control performance is recovered. I will conclude by discussing ongoing extensions to multi-qubit settings and implications for fault-tolerant quantum computation.

Keywords: Open quantum systems; Quantum noise; Quantum control