35 research outputs found
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
Realizing quantum Ising models in tunable two-dimensional arrays of single Rydberg atoms
Spin models are the prime example of simplified manybody Hamiltonians used to
model complex, real-world strongly correlated materials. However, despite their
simplified character, their dynamics often cannot be simulated exactly on
classical computers as soon as the number of particles exceeds a few tens. For
this reason, the quantum simulation of spin Hamiltonians using the tools of
atomic and molecular physics has become very active over the last years, using
ultracold atoms or molecules in optical lattices, or trapped ions. All of these
approaches have their own assets, but also limitations. Here, we report on a
novel platform for the study of spin systems, using individual atoms trapped in
two-dimensional arrays of optical microtraps with arbitrary geometries, where
filling fractions range from 60 to 100% with exact knowledge of the initial
configuration. When excited to Rydberg D-states, the atoms undergo strong
interactions whose anisotropic character opens exciting prospects for
simulating exotic matter. We illustrate the versatility of our system by
studying the dynamics of an Ising-like spin-1/2 system in a transverse field
with up to thirty spins, for a variety of geometries in one and two dimensions,
and for a wide range of interaction strengths. For geometries where the
anisotropy is expected to have small effects we find an excellent agreement
with ab-initio simulations of the spin-1/2 system, while for strongly
anisotropic situations the multilevel structure of the D-states has a
measurable influence. Our findings establish arrays of single Rydberg atoms as
a versatile platform for the study of quantum magnetism.Comment: This is the version of the manuscript as initially submitted to
Natur
Topologically protected edge states in small Rydberg systems
We propose a simple setup of Rydberg atoms in a honeycomb lattice which gives
rise to topologically protected edge states. The proposal is based on the
combination of dipolar exchange interaction, which couples the internal angular
momentum and the orbital degree of freedom of a Rydberg excitation, and a
static magnetic field breaking time reversal symmetry. We demonstrate that for
realistic experimental parameters, signatures of topologically protected edge
states are present in small systems with as few as 10 atoms. Our analysis paves
the way for the experimental realization of Rydberg systems characterized by a
topological invariant, providing a promising setup for future application in
quantum information.Comment: 6 pages, 6 figure
Analysis of imperfections in the coherent optical excitation of single atoms to Rydberg states
We study experimentally various physical limitations and technical
imperfections that lead to damping and finite contrast of optically-driven Rabi
oscillations between ground and Rydberg states of a single atom. Finite
contrast is due to preparation and detection errors and we show how to model
and measure them accurately. Part of these errors originates from the finite
lifetime of Rydberg states and we observe its -scaling with the principal
quantum number . To explain the damping of Rabi oscillations, we use simple
numerical models, taking into account independently measured experimental
imperfections, and show that the observed damping actually results from the
accumulation of several small effects, each at the level of a few percents. We
discuss prospects for improving the coherence of ground-Rydberg Rabi
oscillations in view of applications in quantum simulation and quantum
information processing with arrays of single Rydberg atoms.Comment: 9 pages, 9 figure
Observing the space- and time-dependent growth of correlations in dynamically tuned synthetic Ising antiferromagnets
We explore the dynamics of artificial one- and two-dimensional Ising-like
quantum antiferromagnets with different lattice geometries by using a Rydberg
quantum simulator of up to 36 spins in which we dynamically tune the parameters
of the Hamiltonian. We observe a region in parameter space with
antiferromagnetic (AF) ordering, albeit with only finite-range correlations. We
study systematically the influence of the ramp speeds on the correlations and
their growth in time. We observe a delay in their build-up associated to the
finite speed of propagation of correlations in a system with short-range
interactions. We obtain a good agreement between experimental data and
numerical simulations taking into account experimental imperfections measured
at the single particle level. Finally, we develop an analytical model, based on
a short-time expansion of the evolution operator, which captures the observed
spatial structure of the correlations, and their build-up in time
Ultrafast energy exchange between two single Rydberg atoms on the nanosecond timescale
Rydberg atoms, with their giant electronic orbitals, exhibit dipole-dipole
interaction reaching the GHz range at a distance of a micron, making them a
prominent contender for realizing quantum operations well within their
coherence time. However, such strong interactions have never been harnessed so
far, mainly because of the stringent requirements on the fluctuation of the
atom positions and the necessary excitation strength. Here, using atoms trapped
in the motional ground-state of optical tweezers and excited to a Rydberg state
with picosecond pulsed lasers, we observe an interaction-driven energy
exchange, i.e., a F\"orster oscilation, occuring in a timescale of nanoseconds,
two orders of magnitude faster than in any previous work with Rydberg atoms.
This ultrafast coherent dynamics gives rise to a conditional phase which is the
key resource for an ultrafast controlled- gate. This opens the path for
quantum simulation and computation operating at the speed-limit set by
dipole-dipole interactions with this ultrafast Rydberg platform
Facilitation dynamics and localization phenomena in Rydberg lattice gases with position disorder
We explore the dynamics of Rydberg excitations in an optical tweezer array under anti-blockade (or facilitation) conditions. Due to the finite temperature the atomic positions are randomly spread, an effect that leads to quenched correlated disorder in the interatomic interaction strengths. This drastically affects the facilitation dynamics as we demonstrate experimentally on the elementary example of two atoms. To shed light on the role of disorder in a many-body setting we show that here the dynamics is governed by an Anderson-Fock model, i.e. an Anderson model formulated on a lattice with sites corresponding to many-body Fock states. We first consider a one-dimensional atom chain in a limit which is described by a one-dimensional Anderson-Fock model with disorder on every other site, featuring both localized and delocalized states. We then illustrate the effect of disorder experimentally in a situation in which the system maps on a two-dimensional Anderson-Fock model on a trimmed square lattice. We observe a clear suppression of excitation propagation which we ascribe to the localization of the many-body wavefunctions in Hilbert space
Strong Spin-Motion Coupling in the Ultrafast Quantum Many-body Dynamics of Rydberg Atoms in a Mott-insulator Lattice
Rydberg atoms in optical lattices and tweezers is now a well established
platform for simulating quantum spin systems. However, the role of the atoms'
spatial wavefunction has not been examined in detail experimentally. Here, we
show a strong spin-motion coupling emerging from the large variation of the
interaction potential over the wavefunction spread. We observe its clear
signature on the ultrafast, out-of-equilibrium, many-body dynamics of atoms
excited to a Rydberg S state from an unity-filling atomic Mott-insulator. We
also propose a novel approach to tune arbitrarily the strength of the
spin-motion coupling relative to the motional energy scale set by trapping
potentials. Our work provides a new direction for exploring the dynamics of
strongly-correlated quantum systems by adding the motional degree of freedom to
the Rydberg simulation toolbox