Time-resolved scattering of a single photon by a single atom

Abstract

Scattering of light by matter has been studied extensively in the past. Yet, the most fundamental process, the scattering of a single photon by a single atom, is largely unexplored. One prominent prediction of quantum optics is the deterministic absorption of a travelling photon by a single atom, provided the photon waveform matches spatially and temporally the time-reversed version of a spontaneously emitted photon. Here we experimentally address this prediction and investigate the influence of the photon's temporal profile on the scattering dynamics using a single trapped atom and heralded single photons. In a time-resolved measurement of atomic excitation we find a 56(11)% increase of the peak excitation by photons with an exponentially rising profile compared with a decaying one. However, the overall scattering probability remains unchanged within the experimental uncertainties. Our results demonstrate that envelope tailoring of single photons enables precise control of the photon–atom interaction.

Photon bandwidth dependence of light-matter interaction

“…These photons are focused onto a single atom trapped in a far-off-resonant optical dipole trap. From the fraction of photons that are scattered out of this focused excitation mode we can accurately obtain the the transient atomic excitation [13,[31][32][33].…”

“…The transmitted probe mode is then collimated again by a second aspheric lens, subsequently coupled into a single-mode fiber, and sent to the forward detector D f . In previous experiments we determined the spatial overlap of the probe mode with the atomic dipole mode to be Λ ≈ 0.033 [13].…”

“…where Γ 0 is the width of the atomic line of interest and Λ ∈ [0, 1] is the spatial overlap between the excitation and the atomic dipole mode [12,13]. Photons of different temporal envelopes can have identical power spectra -for example, both exponentially rising and falling temporal envelopes lead to a Lorentzian power spectrum.…”

“…For such a photon the probability P e (t) of finding a two-level atom in the excited state is given by [13,23]…”

“…Aside from the potential use in quantum networks, single atoms are also an ideal test bed to study fundamental properties of light-matter interaction. Following up on recent work on time-resolved scattering of photons with exponentially rising and decaying profiles [13], we report in this work on the dependency of single photon scattering on their bandwidth.…”