Measuring photon-photon interactions via photon detection

TL;DR

This paper presents a method to measure photon-photon interactions in complex systems by analyzing photon detection patterns, revealing peaks that correspond to interaction potential and demonstrating quantum effects like entanglement with minimal photons.

Contribution

It introduces a novel measurement technique for strong non-linearities in complex quantum systems using weakly pumped optical modes and photon detection analysis.

Findings

Detected mean-photon number peaks correspond to photon-photon interaction potential.

System exhibits sub-Poissonian photon statistics and entanglement.

Photon switching occurs with less than one photon.

Abstract

The strong non-linearity plays a significant role in physics, particularly, in designing novel quantum sources of light and matter as well as in quantum chemistry or quantum biology. In simple systems, the photon-photon interaction can be determined analytically. However, it becomes challenging to obtain it for more compex systems. Therefore, we show here how to measure strong non-linearities via allowing the sample to interact with a weakly pumped quantized leaking optical mode. We found that the detected mean-photon number versus pump-field frequency shows several peaks. Interestingly, the interval between neighbour peaks equals the photon-photon interaction potential. Furthermore, the system exhibits sub-Poissonian photon statistics, entanglement and photon switching with less than one photon. Finally, we connect our study with existing related experiments.