Quantum state engineering, purification, and number resolved photon detection with high finesse optical cavities

TL;DR

This paper introduces a versatile optical setup using high finesse cavities for projecting, purifying, and detecting photon number states, advancing quantum information processing and entanglement distribution.

Contribution

It presents a novel multi-functional optical scheme capable of generating, purifying, and detecting photon number states with high precision, suitable for quantum networks.

Findings

Enables conditional generation of entangled photon number states

Allows purification of quantum states in communication scenarios

Provides high-fidelity, number-resolved photon detection

Abstract

We propose and analyze a multi-functional setup consisting of high finesse optical cavities, beam splitters, and phase shifters. The basic scheme projects arbitrary photonic two-mode input states onto the subspace spanned by the product of Fock states |n>|n> with n=0,1,2,.... This protocol does not only provide the possibility to conditionally generate highly entangled photon number states as resource for quantum information protocols but also allows one to test and hence purify this type of quantum states in a communication scenario, which is of great practical importance. The scheme is especially attractive as a generalization to many modes allows for distribution and purification of entanglement in networks. In an alternative working mode, the setup allows of quantum non demolition number resolved photodetection in the optical domain.