Phonon distribution measurements on a trapped ion using the Autler-Townes effect”

by Marion Mallweger (Stockholm University)

Wednesday 15 Mar 2023, 10:00 → 12:00 Europe/Stockholm

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

Trapped ion experiments are a promising platform for numerous fields such as quantum
simulation, quantum sensing and quantum information. Due to the confinement of the ions in a harmonic oscillator, created by the trap electrodes and their field, distinct motional modes arise. Most state-of-the-art trapped ion experiments rely on these motional modes. It is therefor essential to characterize the motional quantum state well. Here, a new measurement method of the motional state of the ion will be presented. The method takes advantage of the phonon number dependent coupling strength of an optical transition. When the strong coupling is on a sideband transition between two levels, a weaker probe, coupling to a third level, will experience two possible transitions. This is also known as the Autler-Townes effect. The separation between the Autler-Townes peaks in our scheme depends on the motional state of the ion, thus the transition frequency changes. We use this phonon number dependent shift to characterize the motional state. First we characterize the shift for welldefined Fock states, where we also show that theory and experimental results are in good agreement. Furthermore, we present how this method can be used to characterize a thermal state and obtain the average phonon number using the Autler-Townes effect. The measurement method not only works for trapped ions, but is applicable for any system which is coupled to a harmonic oscillator.”