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Quasar absorption spectral data indicate the presence of a spatial gradientin the electromagnetic fine-structure constant $\alpha$ on cosmological lengthscales. We point out that experiments with accelerometers, including torsionpendula and atom interferometers, can be used as sensitive probes ofcosmological spatial gradients in the fundamental constants of nature, whichgive rise to equivalence-principle-violating forces on test masses. Usinglaboratory data from the E\"ot-Wash experiment, we constrain spatial gradientsin $\alpha$ along any direction to be $| \boldsymbol{\nabla} \alpha / \alpha |< 6.6 \times 10^{-4}~(\textrm{Glyr})^{-1}$ at $95\%$ confidence level. Ourresult represents an order of magnitude improvement over laboratory bounds fromclock-based searches for a spatial gradient in $\alpha$ directed along theobserved cosmological $\alpha$-dipole axis. Improvements to accelerometerexperiments in the foreseeable future are expected to provide sufficientsensitivity to test the cosmological $\alpha$-dipole seen in astrophysicaldata.

Robust laboratory limits on a cosmological spatial gradient in the electromagnetic fine-structure constant from accelerometer experiments