Limits on Preserving Quantum Coherence using Multi-Pulse Control

Abstract

We explore the physical limits of pulsed dynamical decoupling methods for decoherence control as determined by finite timing resources. By focusing on a decohering qubit controlled by arbitrary sequences of $\pi$-pulses, we establish a non-perturbative quantitative upper bound to the achievable coherence for specified maximum pulsing rate and noise spectral bandwidth. We introduce numerically optimized control "bandwidth-adapted" sequences that saturate the performance bound, and show how they outperform existing sequences in a realistic excitonic-qubit system where timing constraints are significant. As a byproduct, our analysis reinforces the impossibility of fault-tolerance accuracy thresholds for generic open quantum systems under purely reversible error control.

6 pages, 4 figures. Updated to match the journal version, including the EPAPS

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Cited by in corpus (1)

• Optimal pulse spacing for dynamical decoupling in the presence of a purely-dephasing spin-bath