Probing spacetime geometry with atoms

by Jerzy Michal Paczos (Stockholm University)

Friday 13 Mar 2026, 13:00 → 15:00 Europe/Stockholm

AlbaNova A3:1003 - Styrelserum/KOMKO (AlbaNova Main Building)

Abstract:
“This thesis examines how atomic quantum systems can be utilized to probe spacetime effects
in regimes where quantum mechanics and general relativity intersect, and how gravitational
phenomena imprint on experimentally accessible observables. The work is based on two
complementary studies. In Article I, we propose an experimental scheme that combines
trapped-atom interferometry with Ramsey interrogation to realize a clock held in a spatial
superposition at two heights in Earth’s gravitational field. Using a path-integral treatment of
interferometric phases and incorporating the internal-energy contribution to mass, we derive
leading relativistic corrections and identify two signatures of proper-time superposition: (i)
oscillations of interferometric visibility and (ii) an effective shift of the clock transition
frequency. We argue that this frequency-shift signature may be within reach of current or
near-term technology, even when visibility changes are too small to resolve. In Article II, we
develop a general framework for spontaneous emission in curved spacetime and apply it to a
gravitational-wave background. We demonstrate that gravitational waves can induce spectral
sidebands and directional modulations in the emitted radiation, and formulate parameter
estimation via Fisher-information-based sensitivity bounds, yielding order-of-magnitude
requirements for detectability under idealized measurement conditions.”