Online
4/10/2022 - 26/9/2022
QuCoM experimentalists continue to hold regular online meetings every second Tuesday of every month. At both experiment sites, Leiden and Southampton, there are setups which are used to detect gravity with levitated masses. These experiments are cryogenic and involved advanced vibration isolation techniques.
Leiden labs are using tantalum superconductors and asymmetric shaped particles to preferentially detect selected oscillation modes, while Southampton is using lead traps and mostly spherical particles. Experimentalists have also been discussing techniques and protocols to acquire data of the motion of levitated particles for highly sensitive force and acceleration detection as well as manipulation techniques to prepare selected states of motion, such as squeezed and cooled thermal states. The intermediate goal is to achieve thermal noise limited motional modes at the temperature of the cryogenic environment.
Presently, most modes are still driven and therefore heated by vibrations coupling into the particle motion. The best results have been achieved with a passive cryogenic system to be close to the thermal noise limit at 300 mK at Southampton. Therefore, vibration isolation strategies are discussed, and knowledge is shared for inverted pendulum GAS filters and other spring-mass type vibration isolation approaches. Leiden University has the most advanced setup on vibration isolation while using a pulsed tube cooled cryostat. A creative idea is to use a liquid-based vibration damper for future improved isolation at low frequencies.
The QuCoM team is also, with occasional participation from theorists across the project team, discussing different ideas for setting up gravity experiments with the source mass implemented inside the cryostat, which will allow to reduce the size of the source mass significantly and likely below the current smallest mass gravity measurement achieved. The main idea is still to use close to resonance excitation of the source mass to enhance detection sensitive and use some sort of mass modulation of the source mass inside the cryostat. Rotation based platforms as well as linear modulation systems are under consideration.