Entangled Light’s Angular Momentum Reveals Relativistic Lorentz Contraction Factors

The behaviour of light fundamentally changes when observed from a moving perspective, a principle central to Einstein’s theory of relativity, and researchers are continually seeking new ways to explore these effects. Fazilah Nothlawala and colleagues at the University of Glasgow, alongside collaborators, now demonstrate how the twisted properties of light, known as orbital angular momentum, can serve as a sensitive probe of relativistic motion. The team exploits the fact that this ‘twisted’ light isn’t constant when viewed from different speeds, and shows that the correlations within entangled photons are altered by the length contraction predicted by relativity. This innovative approach allows for the quantitative measurement of relativistic effects, effectively using light itself as a ruler to measure speeds approaching 99% of the speed of light, and opens up possibilities for new measurement techniques in extreme conditions.

High-capacity information transfer increasingly demands enhanced precision and accuracy in metrology. This research extends orbital angular momentum (OAM) metrology to relativistic scenarios to determine the Lorentz factor of a moving reference frame, exploiting the non-Lorentz invariance of OAM. Researchers demonstrate that correlations of entangled states exhibit a modified joint OAM spectrum due to length contraction, where the rescaling of spatial dimensions alters the orthogonality of the OAM modes themselves. In an emulated experiment, the team confirms the predicted broadening of the OAM spectrum and uses this to quantitatively infer the Lorentz (contraction) factor, reaching experimentally simulated velocities of up to 0. 99c.

Relativistic Effects on Entangled Photon OAM

This document details the theoretical and experimental framework for investigating how relativistic motion affects the observed orbital angular momentum (OAM) spectra of entangled photon pairs. The research explores how the observed OAM distribution changes when one detector is in relative motion to the source. The core goal is to derive the expected joint probability distribution of detected OAM modes when one detector is moving at relativistic speeds. The work builds upon key concepts including OAM, which describes the twist of a photon, and Spontaneous Parametric Down-Conversion (SPDC), a process used to generate entangled photon pairs.

The experimental setup utilizes a SPDC source with a pump laser and nonlinear crystal to generate entangled photons, and coincidence measurements identify entangled photon pairs. The key findings demonstrate how relativistic motion affects the observed OAM spectra, leading to an increased modal spread with the Lorentz factor. The experimental setup verifies the theoretical predictions and investigates relativistic effects on OAM.

Light Twist Reveals Relativistic Length Contraction

Researchers have demonstrated a novel method for measuring relativistic effects, specifically length contraction, using the orbital angular momentum (OAM) of light. This work establishes a direct link between the properties of light carrying OAM and its behaviour in rapidly moving frames of reference, opening new avenues for precision measurement in extreme conditions. The team successfully simulated relativistic scenarios, achieving velocities approaching 99% of the speed of light, and observed a predictable broadening of the OAM spectrum as a consequence of length contraction. By carefully encoding and analyzing the OAM of entangled photons, the researchers were able to quantify the degree of length contraction experienced by a moving observer.

The observed changes in the OAM spectrum directly correlated with the predicted Lorentz factor, a measure of time dilation and length contraction. This approach offers a potentially more precise and versatile alternative to traditional methods for measuring relativistic effects. Future work could explore the application of this technique to study gravitational fields or to investigate the behaviour of entangled photons in extreme environments.

Lorentz Factor from Orbital Angular Momentum Correlations

This research demonstrates a connection between relativistic effects and the orbital angular momentum (OAM) of light, establishing a pathway to quantify the Lorentz factor using OAM correlations. By examining how the OAM spectrum of entangled photons changes under simulated relativistic motion, the team confirmed that length contraction alters the orthogonality of OAM modes, resulting in a broadening of the spectrum. They showed that a direct relationship exists between the Lorentz factor and the observed OAM spectrum, successfully inferring velocities up to 99% of the speed of light in their simulations. The findings offer a novel technique for measurement in relativistic conditions, leveraging the properties of structured light.