Testing gravity's attraction on quantum vacuum: the state of art of ARCHIMEDES experiment (joint PHE/A2C/Theory seminar)

par Annalisa Allocca (Université de Naples)

vendredi 6 nov. 2026, 10:30 → 11:30 Europe/Paris

200/0-Auditorium - Auditorium P. Lehmann (IJCLab)

The Cosmological Constant problem is one of the most persistent unresolved issues in theoretical physics, arising from the fundamental incompatibility between Quantum Field Theory and General Relativity. Addressing this challenge, the Archimedes experiment investigates the potential coupling
between zero-point quantum fluctuations of the electromagnetic field and gravitational interactions. The experiment employs an ultra-sensitive, custom-designed beam-balance to detect gravitational forces acting on suspended samples. These samples undergo vacuum energy modulation via a superconducting phase transition, effectively forming a series of Casimir cavities that exclude specific electromagnetic modes. Should vacuum energy gravitate, the expelled modes would generate an upward force on the samples, analogous to Archimedes’ buoyancy principle in fluids, and measurable as a variation in effective weight.

The expected torque signal from this modulation is on the order of 10⁻¹³ Nm/√Hz. To mitigate environmental interference, the experiment is sited at the SarGrav Laboratories in Sardinia’s Sos-Enattos region, renowned for its exceptionally low seismic noise and selected as a candidate location
for the next-generation Einstein Telescope gravitational wave observatory.

The tilt sensitivity of the Archimedes prototype, which is also installed at the same laboratory, is currently limited by thermal noise. This sensitivity in torque has been measured to be below 10⁻¹² Nm/√Hz within the frequency range of 20 mHz to 70 mHz, placing it among the most sensitive
beam balances in the world within this range. The final setup of the Archimedes experiment is now fully operational: the first data taking of the full experiment at room temperature started on October 2025. Preliminary results already demonstrate the exceptional capabilities of the experimental
apparatus and the remarkably low background noise levels at the experimental site.