Quantum Reconstruction of an Intense Polarization Squeezed Optical State

Abstract

We perform a reconstruction of the polarization sector of the density matrix of an intense polarization squeezed beam starting from a complete set of Stokes measurements. By using an appropriate quasidistribution, we map this onto the Poincaré space providing a full quantum mechanical characterization of the measured polarization state.

Simulations and experiments on polarization squeezing in optical fiber

“…The single-pass squeezing method allows the measurement of greater squeezing as well as the direct and full characterization of the bright Kerr-squeezed beams [33,60]. Both of these traits are visible in Fig.…”

“…This is advantageous for experiments with long acquisition times, i.e. state tomography, and has indeed allowed the reconstruction of the Wigner function of the dark Stokes plane or Kerr-squeezed states [60]. It is crucial to ensure that the measured squeezing did not arise from detector saturation or any other spurious effect.…”

“…This is a unique feature of polarization measurements and has been used to great advantage in many experiments, for example [33,38,39,55,56,57,58,59]. This has also allowed the first characterization of a bright Kerr squeezed state as well as the reconstruction of the polarization variable Q function using polarization measurements [60].…”

Multipolar hierarchy of efficient quantum polarization measures

“…The wave plates effectively perform a displacement of the state that can be described by the operatorD(θ , φ ) = e iθŜ 2 e iφŜ 3 , and (θ , φ ) are angular coordinates on the sphere. The two output of PBS are measured by photon detectors: the photocurrent sum gives directly the eigenvalue ofN, while the difference gives the ob- servableŜ n = n ·Ŝ, where n is the unit vector in the direction (θ , φ ) [29]. Altogether, this indicates that the scheme yields the probability distribution forŜ n , from which we can equivalently infer the moments…”

Unpolarized states and hidden polarization

“…If n is the unit vector in the direction (θ,φ), the operatorŜ n = n ·Ŝ is the observable measured in polarization experiments [25]: coherent states can be alternatively interpreted as eigenstates ofŜ n S n |θ,φ = S|θ,φ , (3.4) from which one can confirm that they saturate the uncertainty relation (2.4) and so they are the minimum uncertainty states in polarization optics. For these states, one can immediately find…”