Orbital angular momentum of entangled photons as a probe for relativistic effects

TL;DR

This paper demonstrates that the orbital angular momentum spectrum of entangled photons can be used as a novel method to measure relativistic effects, specifically the Lorentz factor, by observing spectrum broadening due to length contraction.

Contribution

It introduces a new relativistic metrology technique using entangled photons' OAM spectrum to determine the Lorentz factor, extending OAM applications to relativistic physics.

Findings

Spectrum broadening correlates with relativistic velocity

Experimental simulation confirms theoretical predictions

Lorentz factor can be extracted from OAM spectrum measurements

Abstract

Orbital angular momentum (OAM) as both classical and quantum states of light has proven essential in numerous applications, from high-capacity information transfer to enhanced precision and accuracy in metrology. Here, we extend OAM metrology to relativistic scenarios to determine the Lorentz factor of a moving reference frame, exploiting the fact that OAM is not Lorentz invariant. We show that the joint OAM spectrum from entangled states is modified by length contraction when measured by two observers moving relative to the entanglement source. This relative motion rescales the spatial dimensions, thus breaking the orthogonality of the OAM measurement process and resulting in a broadening of the joint OAM spectrum that can precisely determine the Lorentz factor. We experimentally simulate velocities up to $0.99c$, confirm the predicted broadening, and use the measurement outcomes to extract the Lorentz factor. Our work provides a pathway for novel measurement techniques suitable for relativistic conditions that leverage OAM structured light as a resource.