Bonn 2025 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 2: Quantum Networks, Repeaters, and QKD I (joint session Q/QI)
Q 2.5: Vortrag
Montag, 10. März 2025, 12:15–12:30, AP-HS
Hong-Ou-Mandel interference of photons generated with nanosecond laser pulses from two co-trapped 40Ca+ ions — •Pascal Baumgart, Max Bergerhoff, and Jürgen Eschner — Universität des Saarlandes, Experimentalphysik, 66123 Saarbrücken
Entangling remote quantum memories is an essential step in the realisation of a quantum repeater segment [1]. It requires the ability to create
indistinguishable single photons capable of Hong-Ou-Mandel interference on a beam splitter [2].
When generating single photons by exciting a Raman transition in a single atom, back decays and re-excitations on the driven transition lead to an uncertainty in the photon emission time, degrading
their temporal indistinguishability [3]. A common approach that limits the number of back decays is excitation via short laser pulses, in the order of the excited-state lifetime.
We present a setup to generate few-nanosecond 393-nm laser pulses to excite the S1/2→P3/2→D5/2 Raman transition in single trapped 40Ca+ ions and create single 854-nm photons. Using two ions in the same trap, we demonstrate Hong-Ou-Mandel interference of the
Raman photons. We investigate the dependence of the interference visibility on the pulse length and amplitude, both experimentally
and theoretically.
[1] P. van Loock et al., Adv. Quantum Technol., 3: 1900141 (2020)
[2] D. L. Moehring et al., Nature 449, 68-71 (2007)
[3] P. Müller et al., Phys. Rev. A 96, 023861 (2017)
Keywords: Trapped ions; Indistinguishable photons; Hong-Ou-Mandel interference; Short laser pulses; Quantum repeater