High spatial entanglement via chirped quasi-phase-matched optical parametric down-conversion

TL;DR

This paper demonstrates that engineering the quasi-phase-matching in optical parametric down-conversion can significantly enhance the generation of high-dimensional spatial entanglement, reaching tens of ebits of entropy.

Contribution

It introduces a method to increase spatial entanglement in photon pairs through quasi-phase-matching engineering, surpassing previous limitations.

Findings

Achieved tens of ebits of entanglement entropy.

Enhanced entanglement by optimizing crystal geometry and pump parameters.

Potential for practical implementation of high-dimensional quantum information protocols.

Abstract

By making use of the spatial shape of paired photons, parametric down-conversion allows the generation of two-photon entanglement in a multidimensional Hilbert space. How much entanglement can be generated in this way? In principle, the infinite-dimensional nature of the spatial degree of freedom renders unbounded the amount of entanglement available. However, in practice, the specific configuration used, namely its geometry, the length of the nonlinear crystal and the size of the pump beam, can severely limit the value that could be achieved. Here we show that the use of quasi-phase-matching engineering allows to increase the amount of entanglement generated, reaching values of tens of ebits of entropy of entanglement under different conditions. Our work thus opens a way to fulfill the promise of generating massive spatial entanglement under a diverse variety of circumstances, some more favorable for its experimental implementation.