Indistinguishable photons from a trapped-ion quantum network node
Martin Meraner, Azadeh Mazloom, V. Krutyanskiy, Vojtech Krcmarsky, Josef Schupp, Dario Fioretto, Pavel Sekatski, Tracy E. Northup, Nicolas Sangouard, B. P. Lanyon
Abstract
Trapped atomic ions embedded in optical cavities are a promising platform to enable long-distance quantum networks and their most far-reaching applications. Here we achieve and analyze photon indistinguishability in a telecom-converted ion-cavity system. First, two-photon interference of cavity photons at their ion-resonant wavelength is observed and found to reach the limits set by spontaneous emission. Second, this limit is shown to be preserved after a two-step frequency conversion replicating a distributed scenario, in which the cavity photons are converted to the telecom $C$ band and then back to the original wavelength. The achieved interference visibility and photon efficiency would allow for the distribution and practical verification of entanglement between ion-qubit registers separated by several tens of kilometers.