Experimental tomography of NOON states with large photon numbers

TL;DR

This paper reports the experimental quantum tomography of NOON states with up to four photons, demonstrating high fidelity states generated via mixing coherent and down-converted photons, and analyzing fidelity limitations.

Contribution

It introduces an experimental method for quantum state tomography of NOON states with large photon numbers and characterizes the fidelity constraints in such states.

Findings

Achieved quantum state tomography of NOON states with up to four photons.

Identified the main fidelity limitations due to state overlap and setup transmission.

Applied tomography to characterize correlated photon hole states.

Abstract

We have performed experimental quantum state tomography of NOON states with up to four photons. The measured states are generated by mixing a classical coherent state with spontaneous parametric down-conversion. We show that this method produces states which exhibit a high fidelity with ideal NOON states. The fidelity is limited by the overlap of the two-photon down-conversion state with any two photons originating from the coherent state, for which we introduce and measure a figure of merit. A second limitation on the fidelity set by the total setup transmission is discussed. We also apply the same tomography procedure for characterizing correlated photon hole states.