Southwest Quantum Information and Technology

Random bosonic states for robust quantum metrology

Presenting Author: Jan Kolodynski, ICFO
Contributing Author(s): M. Oszmaniec, R. Augusiak, C. Gogolin, A. Acin, and M. Lewenstein

We study how useful random states are for quantum metrology, i.e., whether they surpass the classical limits imposed on precision in the canonical phase sensing scenario. First, we prove that random pure states drawn from the Hilbert space of distinguishable particles typically do not lead to superclassical scaling of precision even when allowing for local unitary optimization. Conversely, we show that random pure states from the symmetric subspace typically achieve the optimal Heisenberg scaling without the need for local unitary optimization. Surprisingly, the Heisenberg scaling is observed for random isospectral states of arbitrarily low purity and preserved under loss of a fixed number of particles. Moreover, we prove that for pure states, a standard photon-counting interferometric measurement suffices to typically achieve resolutions following the Heisenberg scaling for all values of the phase at the same time. Finally, we demonstrate that metrologically useful states can be prepared with short random optical circuits generated from three types of beam splitters and a single nonlinear (Kerr-like) transformation.

Read this article online: https://arxiv.org/abs/1602.05407

(Session 9b : Friday from 4:45pm - 5:15pm)