Joint subnatural-linewidth and single-photon emission from resonance fluorescence

Abstract

Resonance fluorescence-the light emitted when exciting resonantly a two-level system-is a popular quantum source as it seems to inherit its spectral properties from the driving laser and its statistical properties from the two-level system, thus providing a subnatural-linewidth single-photon source. However, these two qualities do not actually coexist in resonance fluorescence, since an optical target detecting these antibunched photons will either be spectrally broad itself and not benefit from the spectrally narrow source, or match spectrally with the source but in this case the antibunching will be spoiled. We first explain this failure through a decomposition of the field-emission and how this gets affected by frequency resolution. We then show how to restore the sought joint subnatural linewidth and antibunched properties, by interfering the resonance fluorescence output with a coherent beam. We finally discuss how the signal that is eventually generated in this way features a new type of quantum correlations, with a plateau of antibunching which suppresses much more strongly close photon pairs. This introduces a new concept of perfect single-photon source.

Tunable Photon Statistics Exploiting the Fano Effect in a Waveguide

“…Number-state filtering, in which the weighting of the individual number states is controlled, can generate a quantum output state from such a classical coherent input (for instance, via photon blockade [9][10][11][12][13]). The use of interference has emerged as an extremely powerful tool in this regard: it has been shown theoretically that it can be used to realize complex photon statistics in cavity [14][15][16] and waveguide [17,18] quantum electrodynamics (QED), and to generate single photons with simultaneous subnatural linewidth using resonance fluorescence [19]. Experimentally, the photon statistics of a coherent input have been manipulated via quantum interference in the weakly coupled regime of cavity QED [20,21], most recently using the unconventional photon blockade [22].…”

Impact of detuning and dephasing on a laser-corrected subnatural-linewidth single-photon source

“…We have discussed our scheme to produce joint antibunching and subnatural linewidth emission [64] in the presence of dephasing and of a detuning from the emitter with either the driving laser and/or the detector. Not only does this scheme makes these properties hold simultaneously, it also produces perfect antibunching to first order in the driving (that is, g (2) a (0) = 0) which is otherwise possible only by integrating all frequencies, and features a plateau in the time-delayed photon correlations, making such a single-photon source more effectively suppressing coincidences.…”

“…In the following we will discuss and generalise a scheme which we have recently proposed [64] and that achieves such a joint narrow and antibunched emission, in the sense that a detector does collect its light with these two attributes intact. As we will focus on antibunching and spectral width, we can support our analysis of the detection process through a "sensor" that acts as a filter for the emitted light [60].…”

“…When the emission of the two-level system is filtered in frequency, the tails of the incoherent Lorentzian are trimmed out and this spoils the perfect antibunching, that arises from an interference between the coherent and incoherent components [64]. Such an interference can be restored simply by reinstating the original proportion, i.e., the perfect antibunching can be maintained after filtering by reducing the surplus of coherent emission that passes in its entirety through the filter.…”

“…In Ref. [64], we showed that in the case without dephasing and in resonance, when the loss of antibunching due to filtering is corrected with an external laser, the g (2) a (τ ) displays a plateau of perfectly antibunched photons for up to |τ | ≈ 2.5γ σ . This actually confers to such sources an even greater single-photon source character.…”