A prototype differential atom interferometer for fundamental physics

Nature 654, 622-628 (2026) · DOI: 10.1038/s41586-026-10617-1

License: CC BY 4.0.

Abstract

Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for very-long-baseline atom interferometers such as AION, MAGIS, AICE and AEDGE that aim to detect at frequencies at which ground-based and space-borne laser interferometers lose sensitivity. Very-long-baseline atom interferometers look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. The experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87Sr. Thus, we obtain a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the standard quantum limit with no excess noise beyond atom shot noise. The differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, which emulates the conditions expected in a very-long-baseline atom interferometer. We also demonstrate the recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomized conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying very-long-baseline atom interferometers and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter.

Figures

14 panels with data across 3 figures. Each panel page shows the plot, its columns and its files; each data.csv begins with a header naming the paper, the panel, the source, the license and the provenance route.

Fig. 1

• panel (1): Redshift $z$ against merger mass $M$ ($M_{\odot}$) on log-log axes. Dots are simulated mergers: stellar-mass black holes (orange), IMBHs (cyan) and a hypothetical primordial population (violet); curves are the sensitivity contours of AEDGE, AION-km, ET, LIGO and LISA. The print's black background, its white AION-km and AEDGE contours and its epoch labels are not reproduced. data.csv

Fig. 2

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 3

Illustrative figure, no extractable data. Shown in the paper PDF.

Fig. 4

• panel (a-1): Excitation (%) of the bottom (green) and top (orange) atom clouds against the clock laser phase step (rad), without added laser noise, with a fixed Stark shift applied to the top cloud. Upper plot of printed panel (a). data.csv
• panel (a-2): Excitation (%) of the bottom (green) and top (orange) atom clouds against the clock laser phase step (rad), with artificial laser noise added, with a fixed Stark shift applied to the top cloud. Lower plot of printed panel (a). data.csv
• panel (b): Top excitation (%) against bottom excitation (%), the Lissajous figure of the two atom-interferometer signals, without (LLN, red) and with (HLN, blue) added laser noise. data.csv
• panel (c): Overlapping Allan deviation of $\delta\phi$ (mrad) against measurement time (s) on log-log axes for the LLN and HLN datasets, with error bars. Gray lines are the edges of the 68% and 95% bounds on a Monte Carlo SQL prediction, which the print fills as gray bands; the black dotted line is the SQL $1/\sqrt{\tau}$ averaging. data.csv
• panel (c-inset): Inset of printed panel (c): the standard error $\sigma_{\langle\delta\phi\rangle}$ ($\mu$rad) of the differential phase for the HLN and LLN datasets and the SQL Cramer-Rao bound, with error bars. The print draws the three as a horizontal strip with their labels on the vertical axis. data.csv

Fig. 5

• panel (a-1): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 100 $\mu$Hz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 1 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-2): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 300 $\mu$Hz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 2 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-3): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 1 mHz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 3 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-4): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 3 mHz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 4 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-5): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 10 mHz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 5 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-6): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 30 mHz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 6 of the seven on the broken axis of printed panel (a). data.csv
• panel (a-7): Signal likelihood (arb. units) against frequency (Hz) around the signal injected at 100 mHz: the likelihood extracted from the interferometer output (solid, fitted signal) and a periodogram of the true injected signal (dashed; dotted in the print). Window 7 of the seven on the broken axis of printed panel (a). data.csv
• panel (b): Probability density (norm.) against signal amplitude (mrad): Monte Carlo histograms for SQL-limited measurements of three injected signals, 1 mHz low (black), 100 mHz medium (red) and 1 mHz high, with dashed lines at the amplitudes fitted to the interferometer datasets. The 1 mHz high histogram, black in the print, is dark gray here. data.csv

Ext. Data Fig. 1

The underlying data is not available. The figure is shown in the paper PDF.

Cite

C. F. A. Baynham et al. (107 authors). A prototype differential atom interferometer for fundamental physics. Nature 654, 622-628 (2026). https://doi.org/10.1038/s41586-026-10617-1

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