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.
Highlights
Scattering of light by matter has been studied extensively in the past
The time-reversal symmetry of Schroedinger’s and Maxwell’s equations suggests that the conditions for perfect absorption of an incident single photon by a single atom in free space can be found from the reversed process, the spontaneous emission of a photon from an atom prepared in an excited state[12,13,14,15,16,17,18,19,20]
While the overall scattering probability only depends on the power spectrum, the dynamics depends on the temporal envelope of the incident photon
Summary
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. There, the excited state population decays exponentially with a time constant given by the radiative lifetime t0 of the excited state, and an outwardmoving photon with the same temporal decay profile emerges in a spatial field mode corresponding to the atomic dipole transition[21]. For efficient atomic excitation the incident photon should have an exponentially rising temporal envelope with a matching time constant t0 and propagate in the atomic dipole mode towards the position of the atom[22]. We measure the atomic excited state population dynamics by scattering single photons with identical power spectrum, but different temporal envelopes. While the overall scattering probability only depends on the power spectrum, the dynamics depends on the temporal envelope of the incident
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