Efficient entanglement length measurements for photonic cluster state sources

TL;DR

This paper introduces a passive, efficient method for verifying long photonic cluster states without full state tomography, effective even with low collection efficiencies.

Contribution

It proposes a novel, passive measurement scheme that simplifies and accelerates the verification of entangled photonic cluster states.

Findings

Effective verification at low collection efficiencies

No need for switching optical elements during measurements

Avoids complete state tomography

Abstract

We present a procedure for confirming the generation of long strings of photons in an entangled (cluster) state that does not rely on complete state tomography and that works even at low collection efficiencies. The scheme has the added advantage of being passive - it does not require switching of optical elements to perform measurements in different bases for instance.