When the Bath Remembers: Temporal Correlation, Noise and the Quantum Bath

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Abstract
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Realistic noise processes in quantum systems are often not captured by the probabilistic, Markovian error models commonly used in circuit-level analyses. Here, we investigate how temporally correlated and nonclassical noise affects both quantum control and information Extraction. First, we show that temporally correlated nonclassical noise can make the performance of dynamical decoupling (DD) history dependent. Using an exactly solvable single-qubit model of Gaussian quantum dephasing noise, we demonstrate that the fidelity of a DD-protected gate can depend on control applied at earlier times, even when system-side error propagation is removed through perfect reset operations. This history dependence arises from the evolution of the bath statistics induced by prior control. We then turn this memory effect into a resource for detecting nonclassical noise. We introduce T2-type measurement frameworks incorporating interventions and show how they can reveal nonclassical temporal correlations from time-domain measurements. Together, these results highlight how temporal correlations can both complicate quantum control and provide new opportunities for probing the dynamics of quantum environments.

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About the Speaker
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Nattaphong Wonglakhon is a quantum information researcher who completed his PhD in Howard Wiseman’s group at Griffith University, working on quantum measurement, quantum control, and open quantum systems. His research focused on extracting information from quantum systems and understanding the effects of temporally correlated quantum noise. His current interests include non-Markovian quantum dynamics, quantum sensing, and multi-time quantum processes.