ELFT HÍRADÓ

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

SZFI SeminarNagy DávidWigner RCP SZFIObservation of phase transitions in 
cavity QEDTuesday, 28 February 2023, 10:00, KFKI Campus, Bldg. 1, 2nd floor, 
Conference RoomThe talk overviews recent developments and presents the latest 
experimental results achieved in the Quantum Optics Laboratory of Wigner 
SZFI.A cloud of laser-cooled rubidium atoms is routinely transported into a 
high-finesse optical resonator. The strong collective light-matter coupling 
can be reached even at the limit where a single atom is weakly coupled to the 
field. As a result, the atomic ensemble significantly alters the resonator's 
transmission, which can then be used to monitor the dynamics of this 
nonlinear quantum system. On the other hand, light inside the cavity pumps 
the multilevel atoms into an uncoupled state via a critical runaway process. 
With time-resolved measurements of the cavity output, we can track this 
genuine dynamical transition and measure finite-size scaling relations of the 
enhanced photon number fluctuations. By shining an additional repumper laser 
on the atoms, the two phases of the coupled atom-cavity system can be 
stabilized. They correspond to different hyperfine ground states of the 
atoms, and only one of them is coupled to the cavity mode. Atoms being in 
this latter state block cavity transmission, while the uncoupled state leads 
to high transmission. We demonstrate experimentally that there is a 
bistability region where the two phases coexist. We find a hysteresis in the 
order parameter when either of the two control parameters is swept across the 
bistability region. We interpret the phenomenon in terms of the recent 
paradigm of first-order, driven-dissipative phase transitions.  Join Zoom 
Meetinghttps://wigner-hu.zoom.us/j/87671456898?pwd=N3ZIU0VFekJQanB1NVV4YXNUM1A5Zz09Meeting
 ID: 876 7145 6898Passcode: 682420 Minden érdeklődőt szívesen látunk! - 
Everyone is welcome to attend.Attila Nagysem-admin AT szfki.hu