Polarization-preserving fibers maintain the two polarization states of an orthogonal basis. Quantum communication, however, requires sending at least two nonorthogonal states and these cannot both be preserved. We present a new scheme that allows for using polarization encoding in a fiber not only in the discrete, but also in the continuous-variable regime. For the example of a helically twisted photonic-crystal fibre, we experimentally demonstrate that using appropriate nonorthogonal modes, the polarization-preserving fiber does not fully scramble these modes over the full Poincar\'e sphere, but that the output polarization will stay on a great circle; that is, within a one-dimensional protected subspace, which can be parametrized by a single variable. This will allow for more efficient measurements of quantum excitations in nonorthogonal modes.
@article{arxiv.2305.11220,
title = {Protecting quantum modes in optical fibres},
author = {M. A. T. Butt and P. Roth and G. K. L. Wong and M. H. Frosz and L. L. Sanchez-Soto and E. A. Anashkina and A. V. Andrianov and P. Banzer and P. S. J. Russell and G. Leuchs},
journal= {arXiv preprint arXiv:2305.11220},
year = {2023}
}
Comments
7 pages, 4 figures, accepted in Phys. Rev. Applied