All-optical Quantum Vacuum Signals in Two-Beam Collision

TL;DR

This paper investigates how to detect quantum vacuum nonlinearities through two-beam laser collisions, finding that wider focusing enhances the distinguishability of vacuum signals over background noise.

Contribution

It introduces strategies to optimize the detection of quantum vacuum signals in laser collisions, challenging the assumption that maximum focusing yields the best results.

Findings

Widening laser focus improves signal-to-background separation.

Maximum focusing does not produce the strongest discernible vacuum signal.

Optimal detection strategies depend on beam focusing parameters.

Abstract

The fundamental theory of quantum electrodynamics predicts the vacuum to resemble a polarizable medium. This gives rise to effective nonlinear interactions between electromagnetic fields and light-by-light scattering phenomena. We study the collision of two optical laser pulses in a pump-probe setup using beams with circular and elliptic cross section and estimate the number of discernible signal photons induced by quantum vacuum nonlinearities. In this analysis we study strategies to optimize the quantum vacuum signal discernible from the background of the driving lasers. One of the main results is that the collision of two maximally focused lasers does not lead to the best discernible signal. Instead, widening the focus typically improves the signal to background separation in the far field.