116 research outputs found
Giant optical nonlinearities from Rydberg-excitons in semiconductor microcavities
The realization of exciton-polaritons -- hybrid excitations of semiconductor
quantum well excitons and cavity photons -- has been of great technological and
scientific significance. In particular, the short-range collisional interaction
between excitons has enabled explorations into a wealth of nonequilibrium and
hydrodynamical effects that arise in weakly nonlinear polariton condensates.
Yet, the ability to enhance optical nonlinearities would enable quantum
photonics applications and open up a new realm of photonic many-body physics in
a scalable and engineerable solid-state environment. Here we outline a route to
such capabilities in cavity-coupled semiconductors by exploiting the giant
interactions between excitons in Rydberg-states. We demonstrate that optical
nonlinearities in such systems can be vastly enhanced by several orders of
magnitude and induce nonlinear processes at the level of single photons.Comment: 17 pages, 5 figure
Superglass formation in an atomic BEC with competing long-range interactions
The complex dynamical phases of quantum systems are dictated by atomic
interactions that usually evoke an emergent periodic order. Here, we study a
quantum many-body system with two competing and substantially different
long-range interaction potentials where the dynamical instability towards
density order can give way to a superglass phase, i. e., a superfluid
disordered amorphous solid, which exhibits local density modulations but no
long-range periodic order. We consider a two-dimensional BEC in the
Rydberg-dressing regime coupled to an optical standing wave resonator. The
dynamic pattern formation in this system is governed by the competition between
the two involved interaction potentials: repulsive soft-core interactions
arising due to Rydberg dressing and infinite-range sign changing interactions
induced by the cavity photons. The superglass phase is found when the two
interaction potentials introduce incommensurate length scales. The dynamic
formation of this peculiar phase without any externally added disorder is
driven by quantum fluctuations and can be attributed to frustration induced by
the two competing interaction energies and length scales.Comment: new title, added reference
Quantum gas microscopy of Rydberg macrodimers
A microscopic understanding of molecules is essential for many fields of
natural sciences but their tiny size hinders direct optical access to their
constituents. Rydberg macrodimers - bound states of two highly-excited Rydberg
atoms - feature bond lengths easily exceeding optical wavelengths. Here we
report on the direct microscopic observation and detailed characterization of
such macrodimers in a gas of ultracold atoms in an optical lattice. The size of
about 0.7 micrometers, comparable to the size of small bacteria, matches the
diagonal distance of the lattice. By exciting pairs in the initial
two-dimensional atom array, we resolve more than 50 vibrational resonances.
Using our spatially resolved detection, we observe the macrodimers by
correlated atom loss and demonstrate control of the molecular alignment by the
choice of the vibrational state. Our results allow for precision testing of
Rydberg interaction potentials and establish quantum gas microscopy as a
powerful new tool for quantum chemistry.Comment: 13 pages, 9 figure
Superradiant and subradiant states in lifetime-limited organic molecules through laser-induced tuning
An array of radiatively coupled emitters is an exciting new platform for
generating, storing, and manipulating quantum light. However, the simultaneous
positioning and tuning of multiple lifetime-limited emitters into resonance
remains a significant challenge. Here we report the creation of superradiant
and subradiant entangled states in pairs of lifetime-limited and sub-wavelength
spaced organic molecules by permanently shifting them into resonance with
laser-induced tuning. The molecules are embedded as defects in an organic
nanocrystal. The pump light redistributes charges in the nanocrystal and
dramatically increases the likelihood of resonant molecules. The frequency
spectra, lifetimes, and second-order correlation agree with a simple quantum
model. This scalable tuning approach with organic molecules provides a pathway
for observing collective quantum phenomena in sub-wavelength arrays of quantum
emitters
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