Demonstrating quantum properties of triple photons generated by $$\chi ^3$$ processes

Abstract

Triple photon generation (TPG) is based on a third-order nonlinear optical interaction, which is the most direct way to produce pure quantum three-photon states. These states can exhibit threebody quantum correlations and their statistics cannot be reproduced by any Gaussian statistics of coherent sources or optical parametric twin-photon generator, making them potentially useful for quantum information processing tasks such as quantum state distillation, quantum error-correction and universal quantum computing. Furthermore, the generation of entangled photon pairs heralded by the detection of a third photon can be used in advanced quantum communication protocols. We made the first experimental demonstration of TPG in 2004 using a bi-stimulation scheme in a bulk KTP crystal, followed by the quantum theory. The new challenges are now to achieve a spontaneous TPG and the corresponding quantum experiments and protocols using oriented ridge KTP waveguides, which ensures both birefringence phase-matching and light confinement. The waveguides are cut by a precision dicing saw. We recently performed their characterization using third-harmonic generation measurements, which showed their good quality. A rate of about 5 triplets per second is expected when pumping a 5-cm long waveguide with a 5-W 532 nm beam in the CW regime. Such a spontaneous TPG exhibits low rate of triple photons, which makes the certification of quantum features hard. In this article, we review our theoretical and experimental work on TPG and the associated quantum modeling. We also develop theoretical tools for the certification of quantum features of spontaneous triple photon states.we additionally implement an easily accessible numerical solution to this problem that has not known analytical solution. Finally, we propose new tools in order to characterize quantum features of TPG in section IV, a difficult and important problem under active investigation in several international teams.

Quantum optics of light and matter: honouring Alain Aspect

“…Since entangled pairs of photons were required to demonstrate the "weirdness" of our quantum world, it is natural to consider what three photons might reveal. K. Bencheikh et al describe the generation of triple-photon states [6]. This tri-national work also shines new light on the nonclassical nature of these states.…”