Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 21: Quantum Communication III

Q 21.2: Talk

Tuesday, March 12, 2024, 11:15–11:30, HS 3219

Generation of indistinguishable single photons from a single ⁴⁰Ca⁺-ion using short laser pulses — •Pascal Baumgart, Max Bergerhoff, Stephan Kucera, and Jürgen Eschner — Universität des Saarlandes, Experimentalphysik, 66123 Saarbrücken

Hong-Ou-Mandel interference on a beam splitter, a key step in quantum repeater schemes involving entanglement swapping, requires indistinguishability of single photons [1]. A commonly used method to create single photons from single atoms is continuous laser excitation of a Λ-type Raman transition. This renders indistinguishability difficult, as multiple back-decays and re-excitations on the driven transition, governed by the branching ratio of the excited state, lead to an uncertainty in the photon emission time [2]. An alternative approach that limits the number of back-decays is excitation by short laser pulses, on the order of the excited state lifetime. Using a Raman transition in a single trapped ⁴⁰Ca⁺-ion with an excited state lifetime of 7 ns, we investigate the feasibility of this approach. We present an experimental setup to generate few-nanosecond laser pulses at the excitation wavelength of 393 nm, and we examine the dependence of the photon purity on the pulse length and amplitude.
[1] T. van Leent et al., Nature 607, 2022
[2] P. Müller et al., Phys. Rev. A 96, 2017

Keywords: Trapped ions; Indistinguishable Photons; Short laser pulses