ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarVukics AndrásHUN-REN Wigner RCP SZFIPlaying ball games with a 
cold ensemble: measuring temperature, magnetic field, and gravity in a 
cold-atom cavity QED systemTuesday, 10 June 2025, 10:00, KFKI Campus, Bldg. 
1, 2nd floor, Conference RoomIn this talk, I present recent developments from 
our quantum optics laboratory, aimed at the institute's broad audience. After 
a brief overview of the main components of the experimental system – 
including optics, vacuum, electronics, and the optical cavity – I outline the 
main operational processes: magneto-optical trapping, polarization gradient 
cooling, optical pumping, magnetic trapping and transport. I also describe 
the diagnostic techniques, such as fluorescence and absorption imaging.I show 
how careful image processing allows for determining the optical density, 
center, and spatial extent of the cold-atom cloud. These are essential for 
calculating the atom number and the absolute temperature in Kelvin, since the 
length scale of the image can be determined from the free fall of the cloud 
during time-of-flight.Cold-atom systems have demonstrated great potential in 
the sensing of external fields such as magnetism and gravity. I present a 
novel technique developed in our lab – dubbed "cold-atom buoy" – that 
utilizes the center of mass to determine an external magnetic bias field at 
the position of the cloud arising from the Earth or nearby devices. A micron 
precision in the determination of the center of mass translates to a 
precision on the milli-Gauss scale. This creates a bridge between macroscopic 
magnetic fields and the range of probes based on atomic physics.Finally, I 
will highlight a method that leverages the core feature of our setup, the 
high-finesse optical cavity that can strongly couple to collective atomic 
degrees of freedom. I show how a polarization-resolved single-photon counting 
technique that we have adopted over the past few years allows us to 
differentiate between the density distribution of the atoms in the magnetic 
trap, and the spatial distribution of the trap's magnetic field across the 
sample. Due to gravity, the centers of these distributions are displaced 
relative to each other, enabling the measurement of the gravitational sag of 
a magnetically trapped cold-atom cloud.  Minden érdeklődőt szívesen 
látunk! - Everyone is welcome to attend.Attila Nagysem-admin AT szfki.hu