Distributed Quantum Metrology with Linear Networks and Separable Inputs

Wenchao Ge, Kurt Jacobs, Zachary Eldredge, Alexey V. Gorshkov, and Michael Foss-Feig

Phys. Rev. Lett. 121, 043604 – Published 25 July 2018

Abstract

We derive a bound on the ability of a linear-optical network to estimate a linear combination of independent phase shifts by using an arbitrary nonclassical but unentangled input state, thereby elucidating the quantum resources required to obtain the Heisenberg limit with a multiport interferometer. Our bound reveals that while linear networks can generate highly entangled states, they cannot effectively combine quantum resources that are well distributed across multiple modes for the purposes of metrology: In this sense, linear networks endowed with well-distributed quantum resources behave classically. Conversely, our bound shows that linear networks can achieve the Heisenberg limit for distributed metrology when the input photons are concentrated in a small number of input modes, and we present an explicit scheme for doing so.

Received 20 July 2017

DOI:https://doi.org/10.1103/PhysRevLett.121.043604

Physics Subject Headings (PhySH)

Quantum entanglement Quantum metrology Quantum states of light

Atomic, Molecular & Optical

Authors & Affiliations

Wenchao Ge^1,2, Kurt Jacobs^1,3,4, Zachary Eldredge^5,6, Alexey V. Gorshkov^5,6, and Michael Foss-Feig^1,5,6

¹United States Army Research Laboratory, Adelphi, Maryland 20783, USA
²The Institute for Research in Electronics and Applied Physics (IREAP), College Park, Maryland 20740, USA
³Department of Physics, University of Massachusetts at Boston, Boston, Massachusetts 02125, USA
⁴Hearne Institute for Theoretical Physics, Louisiana State University, Baton Rouge, Louisiana 70803, USA
⁵Joint Quantum Institute, NIST/University of Maryland, College Park, Maryland 20742, USA
⁶Joint Center for Quantum Information and Computer Science, NIST/University of Maryland, College Park, Maryland 20742, USA