Interferometric Constraints on Spacelike Coherent Rotational Fluctuations

TL;DR

This paper reports high-precision interferometric measurements constraining exotic rotational fluctuations of spacetime, achieving quantum-limited sensitivity and providing new bounds on semiclassical models of holographic quantum geometry.

Contribution

It introduces a novel interferometric setup sensitive to rotational spacetime fluctuations and sets unprecedented limits on nonlocal coherent rotational degrees of freedom.

Findings

Achieved quantum-limited sensitivity to rotational signals beyond 3.9 MHz

Set new upper bounds on classical or exotic rotational strain of spacetime

Constrained semiclassical models of holographic quantum geometry

Abstract

Precision measurements are reported of the cross-spectrum of rotationally-induced differential position displacements in a pair of colocated 39 m long, high power Michelson interferometers. One arm of each interferometer is bent $90^{\circ}$ near its midpoint to obtain sensitivity to rotations about an axis normal to the plane of the instrument. The instrument achieves quantum-limited sensing of spatially-correlated signals in a broad frequency band extending beyond the 3.9 MHz inverse light travel time of the apparatus. For stationary signals with bandwidth $\Delta f > 10\;\mathrm{kHz}$, the sensitivity to rotation-induced strain $h$ of classical or exotic origin surpasses $\mathrm{CSD}_{\delta h} < t_P / 2$, where $t_P = 5.39 \times 10^{-44}\;\mathrm{s}$ is the Planck time. This measurement is used to constrain a semiclassical model of nonlocally coherent rotational degrees of freedom of spacetime, which have been conjectured to emerge in holographic quantum geometry but are not present in a classical metric.