211 research outputs found
Methodology for the metric restoration of the historical cartography applied to Francisco Coello's cartografic series of the Royal Site of Aranjuez
Hojas Kilométricas (Kilometric Sheets). Specifically, the study focuses on those sheets referring to the city centre and surrounding area of the Royal Site of Aranjuez, a town in the south of the Province of Madrid. The aim of this study is to restore the actual size and measurements of scanned images of the Hojas Kilométricas. This would allow us, among other things, to reestablish both the format and scale of the original plans. To achieve this goal it is necessary to rectify and then georeference these images, i.e. assign them a geographic reference system. This procedure is essential in the overlaying and comparison of the Hojas Kilométricas of the Royal Site with other historical cartography as well as other sources related to the same area from different time periods. Subsequent research would allow us, for example, to reconstruct the time-evolution of the urban area, to spot new construction and to pinpoint the locations of any altered or missing buildings or architectural features. In addition, this would allow us to develop and integrate databases for GIS models applicable to the management of our cultural heritage
Exponential improvement in photon storage fidelities using subradiance and "selective radiance" in atomic arrays
A central goal within quantum optics is to realize efficient interactions
between photons and atoms. A fundamental limit in nearly all applications based
on such systems arises from spontaneous emission, in which photons are absorbed
by atoms and then re-scattered into undesired channels. In typical treatments
of atomic ensembles, it is assumed that this re-scattering occurs
independently, and at a rate given by a single isolated atom, which in turn
gives rise to standard limits of fidelity in applications such as quantum
memories or quantum gates. However, this assumption can be violated. In
particular, spontaneous emission of a collective atomic excitation can be
significantly suppressed through strong interference in emission. Thus far the
physics underlying the phenomenon of subradiance and techniques to exploit it
have not been well-understood. In this work, we provide a comprehensive
treatment of this problem. First, we show that in ordered atomic arrays in free
space, subradiant states acquire an interpretation in terms of optical modes
that are guided by the array, which only emit due to scattering from the ends
of the finite chain. We also elucidate the properties of subradiant states in
the many-excitation limit. Finally, we introduce the new concept of selective
radiance. Whereas subradiant states experience a reduced coupling to all
optical modes, selectively radiant states are tailored to simultaneously
radiate efficiently into a desired channel while scattering into undesired
channels is suppressed, thus enabling an enhanced atom-light interface. We show
that these states naturally appear in chains of atoms coupled to nanophotonic
structures, and we analyze the performance of photon storage exploiting such
states. We find that selectively radiant states allow for a photon storage
error that scales exponentially better with number of atoms than previously
known bounds.Comment: Fixed minor typos, is now analogous to published versio
Subradiant states of quantum bits coupled to a one-dimensional waveguide
The properties of coupled emitters can differ dramatically from those of
their individual constituents. Canonical examples include sub- and
super-radiance, wherein the decay rate of a collective excitation is reduced or
enhanced due to correlated interactions with the environment. Here, we
systematically study the properties of collective excitations for regularly
spaced arrays of quantum emitters coupled to a one-dimensional (1D) waveguide.
We find that, for low excitation numbers, the modal properties are
well-characterized by spin waves with a definite wavevector. Moreover, the
decay rate of the most subradiant modes obeys a universal scaling with a cubic
suppression in the number of emitters. Multi-excitation subradiant eigenstates
can be built from fermionic combinations of single excitation eigenstates; such
"fermionization" results in multiple excitations that spatially repel one
another. We put forward a method to efficiently create and measure such
subradiant states, which can be realized with superconducting qubits. These
measurement protocols probe both real-space correlations (using on-site
dispersive readout) and temporal correlations in the emitted field (using
photon correlation techniques).Comment: 21 pages, 9 figure
Population mixing due to dipole-dipole interactions in a 1D array of multilevel atoms
We examine theoretically how dipole-dipole interactions arising from multiple
photon scattering lead to a modified distribution of ground state populations
in a driven, ordered 1D array of multilevel atoms. Specifically, we devise a
level configuration in which a ground-state population accumulated due solely
to dipole-dipole interactions can be up to 20\% in regimes accessible to
current experiments with neutral atom arrays. For much larger systems, the
steady state can consist of an equal distribution of population across the
ground state manifold. Our results illustrate how dipole-dipole interactions
can be accentuated through interference, and regulated by the geometry of
ordered atom arrays. More generally, control techniques for multilevel atoms
that can be degraded by multiple scattering, such as optical pumping, will
benefit from an improved understanding and control of dipole-dipole
interactions available in ordered arrays.Comment: paper is now identical to published versio
Optimization of photon storage fidelity in ordered atomic arrays
A major application for atomic ensembles consists of a quantum memory for
light, in which an optical state can be reversibly converted to a collective
atomic excitation on demand. There exists a well-known fundamental bound on the
storage error, when the ensemble is describable by a continuous medium governed
by the Maxwell-Bloch equations. The validity of this model can break down,
however, in systems such as dense, ordered atomic arrays, where strong
interference in emission can give rise to phenomena such as subradiance and
"selective" radiance. Here, we develop a general formalism that finds the
maximum storage efficiency for a collection of atoms with discrete, known
positions, and a given spatial mode in which an optical field is sent. As an
example, we apply this technique to study a finite two-dimensional square array
of atoms. We show that such a system enables a storage error that scales with
atom number like ,
and that, remarkably, an array of just atoms in principle allows
for an efficiency comparable to a disordered ensemble with optical depth of
around 600.Comment: paper is now identical to published versio
Dissipative stabilization of dark quantum dimers via squeezed vacuum
Understanding the mechanism through which an open quantum system exchanges
information with an environment is central to the creation and stabilization of
quantum states. This theme has been explored recently, with attention mostly
focused on system control or environment engineering. Here, we bring these
ideas together to describe the many-body dynamics of an extended atomic array
coupled to a squeezed vacuum. We show that fluctuations can drive the array
into a pure dark state decoupled from the environment. The dark state is
obtained for an even number of atoms and consists of maximally entangled atomic
pairs, or dimers, that mimic the behavior of the squeezed field. Each pair
displays reduced fluctuations in one polarization quadrature and amplified in
another. This dissipation-induced stabilization relies on an efficient transfer
of correlations between pairs of photons and atoms. It uncovers the mechanism
through which squeezed light causes an atomic array to self-organize and
illustrates the increasing importance of spatial correlations in modern quantum
technologies where many-body effects play a central role
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