Eur. Phys. J. D (2012) 66: 288
https://doi.org/10.1140/epjd/e2012-30037-1

Regular Article

Extracting spatial information from noise measurements of multi-spatial-mode quantum states

Quantum Measurement Division, National Institute of Standards and Technology, 20899 Gaithersburg, MD, USA and Joint Quantum Institute, NIST and the University of Maryland, 20899 Gaithersburg, MD, USA

^a e-mail: marino@ou.edu

Received: 15 January 2012
Received in final form: 3 September 2012
Published online: 27 November 2012

Abstract

We show that it is possible to use the spatial quantum correlations present in twin beams to extract information about the shape of a binary amplitude mask in the path of one of the beams. The scheme, based on noise measurements through homodyne detection, is useful in the regime where the number of photons is low enough that direct detection with a photodiode is difficult but high enough that photon counting is not an option. We find that under some conditions the use of quantum states of light leads to an enhancement of the sensitivity in the estimation of the shape of the mask over what can be achieved with a classical state with equivalent properties (mean photon flux and noise properties). In addition, we show that the level of enhancement that is obtained is a result of the quantum correlations and cannot be explained with only classical correlations.