All-optical input-agnostic polarization transformer via experimental Kraus-map control

Abstract

The polarization of light is utilized in many technologies throughout science and engineering. The ability to transform one state of polarization to another is a key enabling technology. Common polarization transformers are simple polarizers and polarization rotators. Simple polarizers change the intensity depending on the input state and can only output a fixed polarized state, while polarization rotators rotates the input Stokes vector in the 3D Stokes space. We demonstrate an all-optical input-agnostic polarization transformer (AI-APT), which transforms all input states of polarization to a particular state that can be polarized or partially polarized. The output state of polarization and intensity depends solely on setup parameters, and not on the input state, thereby the AI-APT functions differently from simple polarizers and polarization rotators. The AI-APT is completely passive, and thus can be used as a polarization controller or stabilizer for single photons and ultrafast pulses. The AI-APT may open a new frontier of partially polarized ultrafast optics.

Robust Free-Space Optical Communication Utilizing Polarization for the Advancement of Quantum Communication

“…We also confirm this via simulations in Appendix A. This would suggest that the polarization of light could serve as a useful degree of freedom in FSO communications, particularly given that polarization transformers have been shown to be able to manipulate the state and degree of polarization (SOP and DOP, respectively) [21] in ways that may be suitable for FSO communications [22]. It has also been shown that polarization can be used to encode and transmit information securely [23], and that states with a DOP of 1 are preserved in the presence of turbulence [16,24].…”

“…The desired partially polarized states are generated by a Mach-Zehnder interferometer, where a polarizing beamsplitter generates beams of horizontal and vertical polarizations, which are then recombined on a 50:50 non-polarizing beamsplitter (BS), such that they are separated by a small distance and not coaxially superposing. This allows for control over the DOP by adjusting relative intensity of each arm of the interferometer [21,32]. This is done by attenuating one arm by tuning a variable neutral-density filter.…”

Quantum Polarimetry

“…As with all paradoxes in the technical sense of the word, a resolution awaits. The creation of such an input-agnostic polarization transformer from linear optical devices requires postselection to enable a lossless polarizer (Zhang et al, 2021); in actuality, some light is always lost by such a polarizer. Such a transformation with Kraus operators enacting Eq.…”

“…Quantum polarization has been used for quantum key distribution (Bennett et al, 1992;Muller et al, 1993), Einstein-Podolsky-Rosen tests (Kwiat et al, 1995), quantum teleportation (Bouwmeester et al, 1997), quantum tomography (James et al, 2001), weak value amplification (Hallaji et al, 2017), and more. However, the study of the changes in quantum polarization have not, to our knowledge, been the focus of any major review, which is a void that must especially be filled due to the proliferation of recent experiments on polarimetry with explicitly quantum mechanical states of light (Altepeter et al, 2011;Bogdanov et al, 2004;Daryanoosh et al, 2018;Graham et al, 2006;Mitchell et al, 2004;Oza et al, 2010;Rosskopf et al, 2020;Slussarenko et al, 2017;Sun et al, 2020;Toussaint et al, 2004;Yoon et al, 2020;Zhang et al, 2021). We set forth to present a complete picture of quantum polarimetry in this work.…”