Programmable two-photon quantum interference in $10^3$ channels in opaque scattering media

TL;DR

This paper demonstrates programmable two-photon quantum interference in a highly scattering medium with thousands of channels, enabling tunable quantum effects for advanced quantum information applications.

Contribution

It introduces a method to control and program two-photon interference in an opaque medium using adaptive wavefront shaping, expanding the capabilities of complex scattering systems for quantum computing.

Findings

Achieved programmable two-photon interference in 10^3 channels.

Demonstrated tunable quantum interference from bunching to antibunching.

Established opaque media as a platform for high-dimensional quantum interference.

Abstract

We investigate two-photon quantum interference in an opaque scattering medium that intrinsically supports $10^6$ transmission channels. By adaptive spatial phase-modulation of the incident wavefronts, the photons are directed at targeted speckle spots or output channels. From $10^3$ experimentally available coupled channels, we select two channels and enhance their transmission, to realize the equivalent of a fully programmable $2\times2$ beam splitter. By sending pairs of single photons from a parametric down-conversion source through the opaque scattering medium, we observe two-photon quantum interference. The programmed beam splitter need not fulfill energy conservation over the two selected output channels and hence could be non-unitary. Consequently, we have the freedom to tune the quantum interference from bunching (Hong-Ou-Mandel-like) to antibunching. Our results establish opaque scattering media as a platform for high-dimensional quantum interference that is notably relevant for boson sampling and physical-key-based authentication.