Single quantum correlation emission spectroscopy: subnatural resolution via quantum interference

P. L. Knight, PAUL M. RADMORE, Piers Coleman

Lukas Hanschke, Lucas Schweickert, Juan Camilo López Carreño +14 more

Resonance fluorescence has played a major role in quantum optics with predictions and later experimental confirmation of nonclassical features of its emitted light such as antibunching or squeezing. In the Rayleigh regime where most of the light originates from the scattering of photons with subnatural linewidth, antibunching would appear to coexist with sharp spectral lines. Here, we demonstrate that this simultaneous observation of subnatural linewidth and antibunching is not possible with simple resonant excitation. Using an epitaxial quantum dot for the two-level system, we independently confirm the single-photon character and subnatural linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our observation is explained by antibunching originating from photon-interferences between the coherent scattering and a weak incoherent signal in a skewed squeezed state. This prefigures schemes to achieve simultaneous subnatural linewidth and antibunched emission.

Stanislav O. Konorov, Xiaoji G. Xu, John W. Hepburn +1 more

High-peak-power ultrafast lasers are widely used in nonlinear spectroscopy, but often limit its spectral resolution because of the broad frequency bandwidth of ultrashort laser pulses. Improving the resolution by achieving spectrally narrow excitation of, or emission from, the resonant medium by means of multiphoton interferences has been the focus of many recent developments in ultrafast spectroscopy. We demonstrate an alternative approach in which high resolution is exercised by detecting narrow spectral correlations between broadband excitation and emission optical fields. All-optical correlation analysis, easily incorporated into a traditional spectroscopic setup, enables direct, robust, and simultaneous detection of multiple narrow resonances in a single measurement.

Prasanta Kumar Panigrahi, Chiranjib Mitra

H. M. Castro-Beltrán, R. Román-Ancheyta

We obtain time-resolved spectra of spontaneous emission and resonance fluorescence of a single multilevel emitter where two antiparallel transitions interfere and cause quantum beats. After rising as a single broad peak, the spontaneous emission spectrum turns into a doublet of subnatural peaks and then fades for long times. For strong field resonance fluorescence, the beat signature is the formation of doublet sidebands, which initially grow asymmetrically but end up symmetrical. We stress the filter bandwidth's crucial role in the spectral resolution and causal evolution.

Mikhail D. Lukin