3D imaging of the biphoton spatiotemporal wave packet

TL;DR

This paper introduces a novel all-optical 3D imaging technique for detailed characterization of biphoton spatiotemporal wave packets, enabling the observation of complex correlations in quantum light fields.

Contribution

The study presents a new high-efficiency, self-referenced method for 3D imaging of quantum biphoton wave packets, overcoming previous technical limitations.

Findings

Successfully observed spatial-spatial correlations in biphotons

Revealed spectral-spectral correlations in quantum light

Mapped spatiotemporal correlations, showing rich structure

Abstract

Photons are among the most important carriers of quantum information owing to their rich degrees of freedom (DoFs), including various spatiotemporal structures. The ability to characterize these DoFs, as well as the hidden correlations among them, directly determines whether they can be exploited for quantum tasks. While various methods have been developed for measuring the spatiotemporal structure of classical light fields, owing to the technical challenges posed by weak photon flux, there have so far been no reports of observing such structures in their quantum counterparts, except for a few studies limited to correlations within individual DoFs. Here, we propose and experimentally demonstrate a self-referenced, high-efficiency, and all-optical method, termed 3D imaging of photonic wave packets, for comprehensive characterization of the spatiotemporal structure of a quantum light field, i.e., the biphoton spatiotemporal wave packet. Benefiting from this developed method, we successfully observe the spatial-spatial, spectral-spectral, and spatiotemporal correlations of biphotons generated via spontaneous parametric down-conversion, revealing rich local and nonlocal spatiotemporal structure in quantum light fields. This method will further advance the understanding of the dynamics in nonlinear quantum optics and expand the potential of photons for applications in quantum communication and quantum computing.