An optimal photon counting polarimeter

Abstract

We present experimental results on a method to perform polarimetry on ensembles of single photons. Our setup is based on a measurement method known to be optimal for estimating the state of two level systems. The setup has no moving parts and is sensitive to weak sources (emitting single photons) of light as it relies on photon counting and has potential applications in both classical polarization measurements and quantum communication scenarios. In our implementation, we are able to reconstruct the Stokes parameters of pure polarization states with an average fidelity of 99.9%.Polarization measurement (also called polarimetry) is fundamental for many optical measurement techniques. In classical optics, applications include stress measurement, magnetic field sensing and optical thin film characterization [1]. More recently, polarization measurement of single photons prepared in particular ways has allowed experimental tests of non-locality and enabled applications in the field of quantum communication and information processing.The purpose of this paper is to report on an implementation of an optimal polarimeter without moving parts suitable for accurate polarization measurement at faint light (single photon) levels. Polarimetry is usually performed using a combination of rotating wave plates and a linear polarizer. Implementations without moving parts to ensure speed and reliability have been reported before [2,3] and exhaustive research has been performed on optimizing them [4,5,6,7,8]. Both types of polarimeters are applicable to complete state estimation techniques (also called state tomography) which are of interest in quantum information.Optimal polarimeters have been studied recently in the context of quantum key distribution [10,12] where the concern is to obtain the best possible estimate on the polarization state of a limited collection of photons. While tomographic techniques are fairly common in quantum optics and related areas [11], it should be noted that classical optics has used such techniques ever since Stokes showed how to determine

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