Tunable decoherence of quantum polarization states via birefringence-frequency coupling using liquid crystal

We theoretically investigate a novel mechanism for controlling the quantum degree of polarization of single- and multi-photon light fields through the combined effects of birefringence and dispersion in optical media. While birefringence alone introduces a unitary phase shift between horizontal (H) and vertical (V) polarization modes, the inclusion of dispersion produces frequency-dependent effects that couple polarization with spectral degrees of freedom, thereby inducing decoherence and transforming the quantum state into a mixed state. By employing an electro-optically controlled nematic liquid crystal as the birefringent medium, this decoherence process can be harnessed to achieve tunable control of the quantum degree of polarization. We model this voltage-dependent tunability theoretically and propose methods for experimental verification.