📝 SummarXiv

Abstract

Detecting the faint signal of continuous gravitational waves (CWs) stands as a major frontier in gravitational-wave astronomy, pushing the need for detectors whose sensitivity exceeds the standard quantum limit (SQL). Here, we propose an orbital optomechanical (OOM) sensor that exploits the sensitive coupling of an orbitally squeezed $p$-orbital Bose-Einstein condensate to spacetime distortions, enabling the detection of interferometer phase shifts induced by CWs. This sensor achieves a theoretical quantum-noise-limited sensitivity 16 dB below the SQL while reducing the required laser power by five orders of magnitude. The performance arises from a novel noise trade-off: a counter-propagating readout scheme suppresses photonic shot noise, while orbital squeezing minimizes the remaining atomic projection noise. By leveraging quantum control over atomic orbital degrees of freedom, this approach establishes a new framework for interferometric sensing with direct applications to the search for CWs and ultralight dark matter.