Ion-Based Quantum Sensor for Optical Cavity Photon Numbers
Moonjoo Lee, Konstantin Friebe, Dario Fioretto, Klemens Schüppert, Florian R. Ong, David Plankensteiner, Valentin Torggler, Helmut Ritsch, R. Blatt, Tracy E. Northup · Physical Review Letters · 2019
We dispersively couple a single trapped ion to an optical cavity to extract information about the cavity photon-number distribution in a nondestructive way. The photon-number-dependent ac Stark shift experienced by the ion is measured via Ramsey spectroscopy. We use these measurements first to obtain the ion-cavity interaction strength. Next, we reconstruct the cavity photon-number distribution for coherent states and for a state with mixed thermal-coherent statistics, finding overlaps above 99% with the calibrated states.