Characterization of a spatial light modulator as a polarization quantum channel

Abstract

Spatial light modulators are versatile devices employed in a vast range of applications to modify the transverse phase or amplitude profile of an incident light beam. Most experiments are designed to use a specific polarization which renders optimal sensitivity for phase or amplitude modulation. Here we take a different approach and apply the formalism of quantum information to characterize how a phase modulator affects a general polarization state. In this context, the spatial modulators can be exploited as a resource to couple the polarization and the transverse spatial degrees of freedom. Using a quasimonochromatic single-photon beam obtained from a pair of twin photons generated by spontaneous parametric down conversion, we performed quantum process tomography in order to obtain a general analytic model for a quantum channel that describes the action of the device on the polarization qubits. We illustrate the application of these concepts by demonstrating the implementation of a controllable phase flip channel. This scheme can be applied in a straightforward manner to characterize the resulting polarization states of different types of phase or amplitude modulators and motivates the combined use of polarization and spatial degrees of freedom in innovative applications.

Optical integration of a real-valued function by measurement of a Stokes parameter

“…This polarization dependent action of the SLM circumvents the need to build an interferometer using a PBS (as shown schematically in Fig.1(a)), resulting in a very stable setup. Moreover, the coherence length required for coherent operation is very small, as decoherence effects induced by the SLM are practically negligible [18]. Two spherical lenses are used to map the reflected light field onto a power meter.…”

“…The SLM introduces a phase noise, which reduces the visibility of the polarization interference. This type of effect has been analyzed in [18]. The main effect of this noise in terms of the integration method is to decrease the signal to noise ratio, so that the overall intensity must be increased to achieve a certain precision in the evaluation of the integral.…”

Ancilla-Assisted Measurement of Photonic Spatial Correlations and Entanglement

“…The boxes α and β represent lens systems that map either the near-field (α; β ¼ π) or far-field (α; β ¼ π=2) spatial distributions of the source onto the SLMs. The action of the SLM on the monochromatic single-photon field can be described as [25] S ¼ jHi hHj ⊗ U þ jVi hVj ⊗ I. A second set of HWPs and polarizing beam splitters are used to project onto the polarization states jAEi.…”

Experimental simulation of decoherence in photonics qudits

“…In particular, we simulate two types of decoherence mechanisms namely dephasing 22 and amplitude damping 23 , by means of a spatial light modulator (SLM) employed to implement operations on the qudit states. A wide variety of applications extend the use of SLMs for controlled manipulation of photonic quantum systems encoded, for instance, in polarization 24 , in orbital angular momentum 25 26 or in transverse momenta of the photons 27 28 29 30 31 32 33 .…”