Quantum metrology in the presence of spatially correlated noise: Restoring Heisenberg scaling

Understand

Environmental noise can hinder the metrological capabilities of entangled states.

• While the use of entanglement allows for Heisenberg-limited resolution, the largest permitted by quantum mechanics, deviations from strictly unitary dynamics quickly restore the standard scaling dictated by the central limit theorem.
• Product and maximally entangled states become asymptotically equivalent when the noisy evolution is both local and strictly Markovian.
• However, temporal correlations in the noise have been shown to lift this equivalence while fully (spatially) correlated noise allows for the identification of decoherence free subspaces.