Title: A single emitter emitting resonance fluorescence into a coherent beam

Speaker: Mr Tomas Lamich, ICFO, Spain

Abstract:
Resonance fluorescence from a single emitter is a paradigmatic quantum light source, in which a twolevel system is coherently driven by laser light, and in response emits light that is anti-bunched, squeezed, and entangled. In 2021, Goncalves et al. [1] studied a variant of resonance fluorescence, in which the driven single emitter is placed in a probe beam containing a weak coherent state, a scenario that allows for both interference of laser light against resonance fluorescence, and stimulated emission by a single emitter.
We present an experimental implementation of the Goncalves et al. scheme, focussing on the exotic non-classical correlations produced in this way. A number of interesting and potentially useful features are predicted by Goncalves et al., including (under different conditions of pump-probe relative phase and power) the complete extinction of the probe, amplification of the probe and generation of extremes of antibunching and bunching, i.e., g(2) approaching zero or infinity. The predictions for transmitted power and g(2) can be given in terms of a single parameter, an effective coupling efficiency suggesting that interference can be used to make up for geometrical and technical limitations on the coupling to single atoms.
We use a single atom far-off-resonance trap in a “Maltese cros” geometry of four high numerical aperture lenses [2] to realise the interaction between a 87Rb atom, a strong pump beam, and a weak probe beam as described in the proposed scheme [1]. We will present a scheme for using the transmission measurement not only to show the interference effects but also to sort individual atoms based on the relative pump-probe phase at the moment of measurement, thus achieving the post-measurement phase stabilisation necessary for the g(2) measurements.

References:
[1] D. Goncalves, M. W. Mitchell, et al. “Unconventional quantum correlations of light emitted by a single atom in free space”. In: Phys. Rev. A 104 (1 2021), p. 013724. doi:10.1103/PhysRevA.104.013724.
[2] L. C. Bianchet, N. Alves, et al. “Manipulating and measuring single atoms in the Maltese cross geometry”. In: Open Research Europe 1.102 (2022). doi: 10.12688/openreseurope.13972.2.