17 research outputs found
Electromagnetically induced transparency of ultralong-range Rydberg molecules
We study the impact of Rydberg molecule formation on the storage and
retrieval of Rydberg polaritons in an ultracold atomic medium. We observe
coherent revivals appearing in the retrieval efficiency of stored photons that
originate from simultaneous excitation of Rydberg atoms and Rydberg molecules
in the system with subsequent interference between the possible storage paths.
We show that over a large range of principal quantum numbers the observed
results can be described by a two-state model including only the atomic Rydberg
state and the Rydberg dimer molecule state. At higher principal quantum numbers
the influence of polyatomic molecules becomes relevant and the dynamics of the
system undergoes a transition from coherent evolution of a few-state system to
an effective dephasing into a continuum of molecular states.Comment: Submitted to PR
Free-Space Quantum Electrodynamics with a single Rydberg superatom
The interaction of a single photon with an individual two-level system is the
textbook example of quantum electrodynamics. Achieving strong coupling in this
system so far required confinement of the light field inside resonators or
waveguides. Here, we demonstrate strong coherent coupling between a single
Rydberg superatom, consisting of thousands of atoms behaving as a single
two-level system due to the Rydberg blockade, and a propagating light pulse
containing only a few photons. The strong light-matter coupling in combination
with the direct access to the outgoing field allows us to observe for the first
time the effect of the interactions on the driving field at the single photon
level. We find that all our results are in quantitative agreement with the
predictions of the theory of a single two-level system strongly coupled to a
single quantized propagating light mode. The demonstrated coupling strength
opens the way towards interfacing photonic and atomic qubits and preparation of
propagating non-classical states of light, two crucial building blocks in
future quantum networks
Photon Subtraction by Many-Body Decoherence
We experimentally and theoretically investigate the scattering of a photonic
quantum field from another stored in a strongly interacting atomic Rydberg
ensemble. Considering the many-body limit of this problem, we derive an exact
solution to the scattering-induced spatial decoherence of multiple stored
photons, allowing for a rigorous understanding of the underlying dissipative
quantum dynamics. Combined with our experiments, this analysis reveals a
correlated coherence-protection process in which the scattering from one
excitation can shield all others from spatial decoherence. We discuss how this
effect can be used to manipulate light at the quantum level, providing a robust
mechanism for single-photon subtraction, and experimentally demonstrate this
capability
Observation of three-body correlations for photons coupled to a Rydberg superatom
We report on the experimental observation of non-trivial three-photon
correlations imprinted onto initially uncorrelated photons through interaction
with a single Rydberg superatom. Exploiting the Rydberg blockade mechanism, we
turn a cold atomic cloud into a single effective emitter with collectively
enhanced coupling to a focused photonic mode which gives rise to clear
signatures in the connected part of the three-body correlation function of the
out-going photons. We show that our results are in good agreement with a
quantitative model for a single, strongly coupled Rydberg superatom.
Furthermore, we present an idealized but exactly solvable model of a single
two-level system coupled to a photonic mode, which allows for an interpretation
of our experimental observations in terms of bound states and scattering
states