27 research outputs found
Photon-Photon Interactions via Rydberg Blockade
We develop the theory of light propagation under the conditions of electromagnetically induced transparency in systems involving strongly interacting Rydberg states. Taking into account the quantum nature and the spatial propagation of light, we analyze interactions involving few-photon pulses. We show that this system can be used for the generation of nonclassical states of light including trains of single photons with an avoided volume between them, for implementing photon-photon gates, as well as for studying many-body phenomena with strongly correlated photons
Learning the Solution Operator of Boundary Value Problems using Graph Neural Networks
As an alternative to classical numerical solvers for partial differential
equations (PDEs) subject to boundary value constraints, there has been a surge
of interest in investigating neural networks that can solve such problems
efficiently. In this work, we design a general solution operator for two
different time-independent PDEs using graph neural networks (GNNs) and spectral
graph convolutions. We train the networks on simulated data from a finite
elements solver on a variety of shapes and inhomogeneities. In contrast to
previous works, we focus on the ability of the trained operator to generalize
to previously unseen scenarios. Specifically, we test generalization to meshes
with different shapes and superposition of solutions for a different number of
inhomogeneities. We find that training on a diverse dataset with lots of
variation in the finite element meshes is a key ingredient for achieving good
generalization results in all cases. With this, we believe that GNNs can be
used to learn solution operators that generalize over a range of properties and
produce solutions much faster than a generic solver. Our dataset, which we make
publicly available, can be used and extended to verify the robustness of these
models under varying conditions
Photonic Phase Gate via an Exchange of Fermionic Spin Waves in a Spin Chain
We propose a new protocol for implementing the two-qubit photonic phase gate.
In our approach, the pi phase is acquired by mapping two single photons into
atomic excitations with fermionic character and exchanging their positions. The
fermionic excitations are realized as spin waves in a spin chain, while photon
storage techniques provide the interface between the photons and the spin
waves. Possible imperfections and experimental systems suitable for
implementing the gate are discussed.Comment: 4 pages, 1 figure. V2: extended the discussion of the main idea,
removed supplementary information and inessential extensions, added
references. V3: slightly modified references and text - final version as
published in Phys. Rev. Let
Dissipative Preparation of Spin Squeezed Atomic Ensembles in a Steady State
We present and analyze a new approach for the generation of atomic spin
squeezed states. Our method involves the collective coupling of an atomic
ensemble to a decaying mode of an open optical cavity. We demonstrate the
existence of a collective atomic dark-state, decoupled from the radiation
field. By explicitly constructing this state we find that it can feature spin
squeezing bounded only by the Heisenberg limit. We show that such dark states
can be deterministically prepared via dissipative means, thus turning
dissipation into a resource for entanglement. The scaling of the phase
sensitivity taking realistic imperfections into account is discussed.Comment: 5 pages, 4 figure
Self-Distilled Representation Learning for Time Series
Self-supervised learning for time-series data holds potential similar to that
recently unleashed in Natural Language Processing and Computer Vision. While
most existing works in this area focus on contrastive learning, we propose a
conceptually simple yet powerful non-contrastive approach, based on the
data2vec self-distillation framework. The core of our method is a
student-teacher scheme that predicts the latent representation of an input time
series from masked views of the same time series. This strategy avoids strong
modality-specific assumptions and biases typically introduced by the design of
contrastive sample pairs. We demonstrate the competitiveness of our approach
for classification and forecasting as downstream tasks, comparing with
state-of-the-art self-supervised learning methods on the UCR and UEA archives
as well as the ETT and Electricity datasets.Comment: Presented at the NeurIPS 2023 Workshop: Self-Supervised Learning -
Theory and Practic
Bose-Einstein condensation of stationary-light polaritons
We propose and analyze a mechanism for Bose-Einstein condensation of
stationary dark-state polaritons. Dark-state polaritons (DSPs) are formed in
the interaction of light with laser-driven 3-level Lambda-type atoms and are
the basis of phenomena such as electromagnetically induced transparency (EIT),
ultra-slow and stored light. They have long intrinsic lifetimes and in a
stationary set-up with two counterpropagating control fields of equal intensity
have a 3D quadratic dispersion profile with variable effective mass. Since DSPs
are bosons they can undergo a Bose-Einstein condensation at a critical
temperature which can be many orders of magnitude larger than that of atoms. We
show that thermalization of polaritons can occur via elastic collisions
mediated by a resonantly enhanced optical Kerr nonlinearity on a time scale
short compared to the decay time. Finally condensation can be observed by
turning stationary into propagating polaritons and monitoring the emitted
light.Comment: 4 pages, 3 figure
Towards Learning Self-Organized Criticality of Rydberg Atoms using Graph Neural Networks
Self-Organized Criticality (SOC) is a ubiquitous dynamical phenomenon
believed to be responsible for the emergence of universal scale-invariant
behavior in many, seemingly unrelated systems, such as forest fires, virus
spreading or atomic excitation dynamics. SOC describes the buildup of
large-scale and long-range spatio-temporal correlations as a result of only
local interactions and dissipation. The simulation of SOC dynamics is typically
based on Monte-Carlo (MC) methods, which are however numerically expensive and
do not scale beyond certain system sizes. We investigate the use of Graph
Neural Networks (GNNs) as an effective surrogate model to learn the dynamics
operator for a paradigmatic SOC system, inspired by an experimentally
accessible physics example: driven Rydberg atoms. To this end, we generalize
existing GNN simulation approaches to predict dynamics for the internal state
of the node. We show that we can accurately reproduce the MC dynamics as well
as generalize along the two important axes of particle number and particle
density. This paves the way to model much larger systems beyond the limits of
traditional MC methods. While the exact system is inspired by the dynamics of
Rydberg atoms, the approach is quite general and can readily be applied to
other systems