Universal bounds for noisy quantum metrology in presence of uncorrelated and correlated noise
by
Francesco Albarelli
→
Europe/Rome
281
281
Description
Title: Universal bounds for noisy quantum metrology in presence of uncorrelated and correlated noise
Abstract
In this talk, I will discuss recent advancements in understanding the ultimate precision limits of noisy quantum metrology for finite-dimensional systems, focusing on scenarios involving N uses of a parameter-encoding channel under the most general adaptive strategies. A key result is the derivation of novel bounds on the quantum Fisher information, based on purifications of the noisy state. These bounds are applicable to both uncorrelated and correlated noise [1].
For uncorrelated noise, the bound is saturable by parallel strategies in the asymptotic regime $N \to \infty$, which demonstrates the equivalence of parallel and adaptive strategies in achieving optimal precision, irrespective of whether Heisenberg scaling is allowed or forbidden by noise [2]. Additionally, this framework provides insights into more unconventional strategies, such as causal superpositions of channels, showing that these do not offer an asymptotic advantage over parallel strategies, even if an advantage for finite number of uses may be present.
For correlated noise, the bounds are not guaranteed to be tight in general, but their tightness may be systematically increased by increasing the numerical complexity of the numerical procedure. Applying this approach to study phase estimation models in the presence of temporally correlated dephasing, we show that i) negative correlations are beneficial for parallel dephasing (no Heisenberg scaling), and ii) the bounds are tight for perpendicular dephasing (Heisenberg scaling).
