259 research outputs found
Experimental investigations of the dipolar interactions between single Rydberg atoms
This review summarizes experimental works performed over the last decade by
several groups on the manipulation of a few individual interacting Rydberg
atoms. These studies establish arrays of single Rydberg atoms as a promising
platform for quantum state engineering, with potential applications to quantum
metrology, quantum simulation and quantum information
Direct measurement of the van der Waals interaction between two Rydberg atoms
We report on the direct measurement of the van der Waals interaction between
two isolated, single Rydberg atoms separated by a controlled distance of a few
micrometers. By working in a regime where the single-atom Rabi frequency of the
laser used for excitation to the Rydberg state is comparable to the interaction
energy, we observe a \emph{partial} Rydberg blockade, whereby the
time-dependent populations of the various two-atom states exhibit coherent
oscillations with several frequencies. A quantitative comparison of the data
with a simple model based on the optical Bloch equations allows us to extract
the van der Waals energy, and to observe its characteristic
dependence. The magnitude of the measured coefficient agrees well with an
\emph{ab-initio} theoretical calculation, and we observe its dramatic increase
with the principal quantum number of the Rydberg state. Our results not
only allow to test an important physical law, but also demonstrate a degree of
experimental control which opens new perspectives in quantum information
processing and quantum simulation using long-range interactions between the
atoms.Comment: 4 pages, 3 figures, published versio
Measurement of the Angular Dependence of the Dipole-Dipole Interaction Between Two Individual Rydberg Atoms at a F\"orster Resonance
We measure the angular dependence of the resonant dipole-dipole interaction
between two individual Rydberg atoms with controlled relative positions. By
applying a combination of static electric and magnetic fields on the atoms, we
demonstrate the possibility to isolate a single interaction channel at a
F\"orster resonance, that shows a well-defined angular dependence. We first
identify spectroscopically the F\"orster resonance of choice and we then
perform a direct measurement of the interaction strength between the two atoms
as a function of the angle between the internuclear axis and the quantization
axis. Our results show good agreement with the expected angular dependence
, and represent an important step towards quantum
state engineering in two-dimensional arrays of individual Rydberg atoms.Comment: 5 pages, 4 figure
Synthetic three-dimensional atomic structures assembled atom by atom
We demonstrate the realization of large, fully loaded, arbitrarily-shaped
three-dimensional arrays of single atoms. Using holographic methods and
real-time, atom-by-atom, plane-by-plane assembly, we engineer atomic structures
with up to 72 atoms separated by distances of a few micrometres. Our method
allows for high average filling fractions and the unique possibility to obtain
defect-free arrays with high repetition rates. These results find immediate
application for the quantum simulation of spin Hamiltonians using Rydberg atoms
in state-of-the-art platforms, and are very promising for quantum-information
processing with neutral atoms.Comment: 5 pages, 3 figure
An atom-by-atom assembler of defect-free arbitrary 2d atomic arrays
Large arrays of individually controlled atoms trapped in optical tweezers are
a very promising platform for quantum engineering applications. However, to
date, only disordered arrays have been demonstrated, due to the
non-deterministic loading of the traps. Here, we demonstrate the preparation of
fully loaded, two-dimensional arrays of up to 50 microtraps each containing a
single atom, and arranged in arbitrary geometries. Starting from initially
larger, half-filled matrices of randomly loaded traps, we obtain user-defined
target arrays at unit filling. This is achieved with a real-time control system
and a moving optical tweezers that performs a sequence of rapid atom moves
depending on the initial distribution of the atoms in the arrays. These results
open exciting prospects for quantum engineering with neutral atoms in tunable
geometries
A non-equilibrium superradiant phase transition in free space
A class of systems exists in which dissipation, external drive and
interactions compete and give rise to non equilibrium phases that would not
exist without the drive. There, phase transitions could occur without the
breaking of any symmetry, yet with a local order parameter, in contrast with
the Landau theory of phase transitions at equilibrium. One of the simplest
driven dissipative quantum systems consists of two-level atoms enclosed in a
volume smaller than the wavelength of the atomic transition cubed, driven by a
light field. The competition between collective coupling of the atoms to the
driving field and their cooperative decay should lead to a transition between a
phase where all the atomic dipoles are phaselocked and a phase governed by
superradiant spontaneous emission. Here, we realize this model using a
pencil-shaped cloud of laser cooled atoms in free space, optically excited
along its main axis, and observe the predicted phases. Our demonstration is
promising in view of obtaining free-space superradiant lasers or to observe new
types of time crystals.Comment: 9 pages, 8 figure
Coherent dipole-dipole coupling between two single atoms at a F\"orster resonance
Resonant energy transfers, i.e. the non-radiative redistribution of an
electronic excitation between two particles coupled by the dipole-dipole
interaction, lie at the heart of a variety of chemical and biological
phenomena, most notably photosynthesis. In 1948, F\"orster established the
theoretical basis of fluorescence resonant energy transfer (FRET), paving the
ground towards the widespread use of FRET as a "spectroscopic ruler" for the
determination of nanometer-scale distances in biomolecules. The underlying
mechanism is a coherent dipole-dipole coupling between particles, as already
recognized in the early days of quantum mechanics, but this coherence was not
directly observed so far. Here, we study, both spectroscopically and in the
time domain, the coherent, dipolar-induced exchange of electronic excitations
between two single Rydberg atoms separated by a controlled distance as large as
15 microns, and brought into resonance by applying a small electric field. The
coherent oscillation of the system between two degenerate pair states occurs at
a frequency that scales as the inverse third power of the distance, the
hallmark of dipole-dipole interactions. Our results not only demonstrate, at
the most fundamental level of two atoms, the basic mechanism underlying FRET,
but also open exciting prospects for active tuning of strong, coherent
interactions in quantum many-body systems.Comment: 4 pages, 3 figure
- âŠ