Heralded single-ion – single-photon interactions
Christoph Kurz, Jan Huwer, Michael Schug, Joyee Ghosh, José Brito, Pascal Eich, Philipp Müller, Stephan Kucera, Jürgen Eschner
Experimentalphysik, Universität des Saarlandes, Campus E2 6, 66123 Saarbrücken, Germany
We study various implementations of controlled interaction between single atoms and single photons in the context of quantum networks.
Specifically, we demonstrate the absorption of a single laser photon by a single trapped atomic ion, mapping the photon polarization state onto the atomic spin state, which is heralded by the detection of a Raman-scattered photon [t.b.p.]. This enables photon-to-atom entanglement transfer .
We also generate single photons with controlled temporal, spectral, and polarization properties through a laser-driven spontaneous Raman process [2-4]. The photons have between ~15 ns and ~1 µs duration and are near-Fourier-limited [2, 3]. In one experiment, single photons from one ion are transmitted over ~1 m distance to a second single ion where they are absorbed; individual absorption events are detected employing a quantum-jump heralding scheme .
In another experiment, we demonstrate heralded absorption by a single trapped ion of single photons from a Spontaneous Parametric Down-Conversion (SPDC) source; the entanglement of the SPDC photon pair is manifested in the polarization correlation between photon absorption and detection of the heralding partner [5, 6].
 Heralded mapping of photonic entanglement into single atoms in free space: proposal for a loophole-free Bell test, N. Sangouard et al., New J. Phys. 15, 085004 (2013)
 Bandwidth-Tunable Single-Photon Source in an Ion-Trap Quantum Network, M. Almendros et al., Phys. Rev. Lett. 103, 213601 (2009)
 A high-rate source for single photons in a pure quantum state, C. Kurz et al., New J. Phys. 15, 055005 (2013)
 Heralded Photonic Interaction between Distant Single Ions, M. Schug et al., Phys. Rev. Lett. 110, 213603 (2013)
 Heralded single-photon absorption by a single atom, N. Piro et al., Nature Physics 7, 17 (2011)
 Photon entanglement detection by a single atom, J. Huwer et al., New J. Phys. 15, 025033 (2013)