Supersensitive Ancilla-Based Adaptive Quantum Phase Estimation

Abstract

The supersensitivity attained in quantum phase estimation is known to be compromised in the presence of decoherence. This is particularly patent at blind spots - phase values at which sensitivity is totally lost. One remedy is to use a precisely known reference phase to shift the operation point to a less vulnerable phase value. Since this is not always feasible, we present here an alternative approach based on combining the probe with an ancillary degree of freedom containing adjustable parameters to create an entangled quantum state of higher dimension. We validate this concept by simulating a configuration of a Mach-Zehnder interferometer with a two-photon probe and a polarization ancilla of adjustable parameters, entangled at a polarizing beam splitter. At the interferometer output, the photons are measured after an adjustable unitary transformation in the polarization subspace. Through calculation of the Fisher information and simulation of an estimation procedure, we show that optimizing the adjustable polarization parameters using an adaptive measurement process provides globally supersensitive unbiased phase estimates for a range of decoherence levels, without prior information or a reference phase.

Publication Date

10-16-2017

Publication Title

Physical Review A

Volume

96

Issue

4

Document Type

Article

Personal Identifier

scopus

DOI Link

https://doi.org/10.1103/PhysRevA.96.042110

Socpus ID

85031735638 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/85031735638

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