Quantifiers of noise reducibility under restricted control
Phys. Rev. A 114, 042406 – Published 6 October, 2026
DOI: https://doi.org/10.1103/29q3-fq6z
Abstract
The correlation structure of multitime quantum processes—succinctly described by quantum combs—is an important resource for many quantum information protocols and control tasks. Inspired by approaches for quantum states, we introduce quantifiers of the practical utility of quantum processes that satisfy monotonicity properties, thus overcoming shortcomings in previous state-motivated approaches. Applying these quantifiers to the problem of noise reduction of a quantum process under open-loop control, they are shown to represent the largest amount of temporal mutual information that a process can possibly exhibit. In addition, we study their resource composition behavior and connect them to the recently introduced notion of generalized comb divergences. Finally, in light of these new quantifiers, we reinterpret the numerical findings of Berk et al. [npj Quantum Inf. 9, 104 (2023)] on the relationship of dynamical decoupling and non-Markovian memory, which were based on insufficient resource quantifiers, and show that their main conclusion—the interpretation of dynamical decoupling as a resource distillation—still holds.
