Symmetry-protection of multiphoton states of light

TL;DR

This paper explores how cylindrical symmetry in scattering problems can protect multiphoton states of light, extending the concept of symmetry-protection beyond single-photon states and highlighting potential quantum communication applications.

Contribution

It formally defines postselected symmetry-protection for multiphoton states and shows these states can be built from a limited set of one- and two-photon states under cylindrical symmetry.

Findings

Protected multiphoton states can be constructed from simple one- and two-photon states.

Symmetry-protected states are not limited to low photon numbers.

Potential applications in decoherence-free subspaces for quantum communication.

Abstract

In this manuscript we analyze the emergence of protected multiphoton states in scattering problems with cylindrical symmetry. In order to do that, we first provide a formal definition of the concept of postselected symmetry-protection. We show that symmetry-protected states are not limited to one- or two-photon states, on the contrary, it can be formally extended to the multiphoton case. In addition, we prove for the case of cylindrical symmetry that all possible multiphoton protected states are constructed from a small set of one- and two-photon states. Finally, we point out possible applications that symmetry-protected states may have in quantum communications, concretely, in the construction of decoherence-free subspaces.