Cryogenic interferometry

Eric Varoquaux, Olivier Avenel, Pertti Juhani Hakonen +1 more

Franklyn Quinlan

The photodetection of ultrashort optical pulse trains has applications in RF and microwave photonics systems that wish to take advantage of the exceptional frequency and timing precision available from optical sources. Room temperature applications include low phase noise microwave generation and sources for very long baseline interferometry, whereas cryogenic applications include driving quantum-based voltage standards and the drive and readout of superconducting qubits. Both room temperature and cryogenic applications of short pulse detection are reviewed.

Francis Procaccia

Theoretical framework for a directionally sensitive quantum inertial sensor exploiting the anisotropic band structure of semi-Dirac topological materials (ZrSiS) coupled with Bose-Einstein Condensate (BEC) interferometry. The sensor achieves target sensitivity <10⁻¹⁰ g drift over 1 hour with directional selectivity exceeding 100:1, addressing fundamental limitations of conventional atom interferometers which lack inherent directional tunability. KEY INNOVATION: Optical coupling mechanism where a differential laser interferometer probes both systems—the BEC provides an ultra-stable phase reference via matter-wave interferometry, while acceleration-induced charge redistribution in the anisotropic lattice modulates the optical path length. The semi-Dirac band structure exhibits orthogonal massive and massless dispersion, enabling directional tuning without mechanical rotation. The system operates with the BEC at nanoKelvin temperatures and the lattice at 2-4 K, coupled optically while maintaining thermal isolation through multi-stage cryogenic architecture. APPLICATIONS: GPS-denied navigation (submarine, underground, contested environments), fundamental physics (gravitational wave detection, geodesy), and compact multi-axis inertial measurement units. CURRENT STATUS: Theoretical framework with quantitative performance predictions. U.S. Provisional Patent filed July 2025. Seeking experimental collaborators with dilution refrigeration and BEC capabilities for proof-of-concept validation. CONTACT: francisprocaccia@proton.me - Open to collaboration inquiries from university groups, national laboratories, and quantum sensor companies.

F. De Martini, G. Denardo, Anton Zeilinger

L. Kleybolte, P. Gewecke, A. Sawadsky +2 more

Squeezed states of light reduce the signal-normalized photon counting noise of measurements without increasing the light power and enable fundamental research on quantum entanglement in hybrid systems of light and matter. Squeezed states of light have high potential to complement cryogenically cooled sensors, whose thermal noise is suppressed below the quantum noise of light by operation at low temperature. They allow us to reduce the optical heat load on cooled devices by lowering the light power without losing measurement precision. Here, we demonstrate the squeezed-light position sensing of a cryo-cooled micromechanical membrane. The sensing precision is improved by up to 4.8 dB below photon counting noise, limited by optical loss, at a membrane temperature of about 20 K. We prove that realizing a high interference contrast in a cryogenic Michelson interferometer is feasible. Our setup is the first conceptual demonstration towards the envisioned European gravitational-wave detector, the "Einstein telescope," which is planned to use squeezed states of light together with cryo-cooled mirror test masses.

Lawrence N. Mertz