arXiv subjects

Enrique Solano

Publications and source records attributed to Enrique Solano.

At least 163 records · Page 9Linked to original sources

arXiv2013

Relativistic Quantum Teleportation with Superconducting Circuits

We study the effects of relativistic motion on quantum teleportation and propose a realizable experiment where our results can be tested. We compute bounds on the optimal fidelity of teleportation when one of the observers undergoes non-uniform motion for a finite time. The upper bound to the optimal fidelity is degraded due to the observer's motion however, we discuss how this degradation can be corrected. These effects are observable for experimental parameters that are within reach of cutting-edge superconducting technology. Our setup will further provide guidance for future space-based experiments.

quant-ph↗

arXiv2013

Proper motions of young stars in Chamaeleon. I. A Virtual Observatory study of spectroscopically confirmed members

(abridged) We want to provide further evidence of the origin of the proposed stellar members of Chamaeleon and to identify interlopers from the foreground εCha and ηCha associations. To this aim, we compile lists of spectroscopically confirmed members of Chamaeleon I and II, εCha and ηCha, and of background objects in the same line of sight. Using Virtual Observatory tools, we cross-match these lists with the UCAC3 catalogue to get the proper motions of the objects. In the vector point diagram, we identify the different moving groups, and use this information to study the membership of proposed candidate members of the associations from the literature. For those objects with available radial velocities, we compute their Galactic space velocities. We look for correlations between the known properties of the objects and their proper motions. The members of the dark clouds exhibit clearly different proper motions from those of the foreground associations and of the background stars. The data suggest that Chamaeleon II could have different dynamical properties from Chamaeleon I. Although the two foreground clusters εand ηChamaeleontis constitute two different proper motion groups, they have similar spatial motions, which are different from the spatial motion of Chamaeleon I. On the other hand, the space motions of the Chamaeleon II stars look more similar to those of the foreground clusters than to the Chamaeleon I stars, but the numbers are low. Hence, with the available data it is unclear to what extent the stellar populations in both clouds are physically connected to each other. We find no correlations between the proper motions and the properties of the objects in either of the clouds.

astro-ph.SR↗

arXiv2013

Dynamical correlation functions and the quantum Rabi model

We study the quantum Rabi model within the framework of the analytical solution developed in Phys. Rev. Lett. 107,100401 (2011). In particular, through time-dependent correlation functions, we give a quantitative criterion for classifying two regions of the quantum Rabi model, involving the Jaynes-Cummings, the ultrastrong, and deep strong coupling regimes. In addition, we find a stationary qubit-field entangled basis that governs the whole dynamics as the coupling strength overcomes the mode frequency.

quant-ph↗

arXiv2012

Red supergiants around the obscured open cluster Stephenson 2

Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum-Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Among them, Stephenson 2, with a core grouping of 26 RSGs, is a strong candidate to be the most massive cluster in the Galaxy. It is located close to a region where a strong over-density of RSGs had been found. We explore the actual cluster size and its possible connection to this over-density. We have performed a cross-match between DENIS, USNO-B1 and 2MASS to identify candidate obscured luminous red stars around Ste 2, and in a control nearby region, finding >600 candidates. More than 400 are sufficiently bright in I to allow observation with a 4-m class telescope. We have observed a subsample of ~250 stars, using AF2 on the WHT telescope in La Palma, obtaining intermediate-resolution spectroscopy in the 7500--9000A range. We derive spectral types and luminosity classes for all these objects and measure their radial velocities. Our targets are G and K supergiants, late (>=M4) M giants, and M-type bright giants (luminosity class II) and supergiants. We find ~35 RSGs with radial velocities similar to Ste 2 members, spread over the two areas surveyed. In addition, we find ~40 RSGs with radial velocities incompatible in principle with a physical association. Our results show that Ste 2 is not an isolated cluster, but part of a huge structure likely containing hundreds of RSGs, with radial velocities compatible with the terminal velocity at this Galactic longitude (and a distance ~6kpc). In addition, we find evidence of several populations of massive stars at different distances along this line of sight [ABRIDGED].

astro-ph.GA↗

arXiv2012

Microwave photonics with Josephson junction arrays: negative refraction index and entanglement through disorder

We study different architectures for a photonic crystal in the microwave regime based on superconducting transmission lines interrupted by Josephson junctions, both in one and two dimensions. A study of the scattering properties of a single junction in the line shows that the junction behaves as a perfect mirror when the photon frequency matches the Josephson plasma frequency. We generalize our calculations to periodic arrangements of junctions, demonstrating that they can be used for tunable band engineering, forming what we call a quantum circuit crystal. Two applications are discussed in detail. In a two-dimensional structure we demonstrate the phenomenon of negative refraction. We finish by studying the creation of stationary entanglement between two superconducting qubits interacting through a disordered media.

quant-ph↗

arXiv2011

Probing biological light-harvesting phenomena by optical cavities

We propose a driven optical cavity quantum electrodynamics (QED) set up aimed at directly probing energy transport dynamics in photosynthetic biomolecules. We show that detailed information concerning energy transfer paths and delocalization of exciton states can be inferred (and exciton energies estimated) from the statistical properties of the emitted photons. This approach provides us with a novel spectroscopic tool for the interrogation of biological systems in terms of quantum optical phenomena which have been usually studied for atomic or solid-state systems, e.g. trapped atoms and semiconductor quantum dots.

physics.bio-ph↗

arXiv2011

A proper motion study of the Lupus clouds using VO tools

Aims: By using kinematical information, we test the membership of the new Lupus candidate members proposed by the Cores to Disks (c2d) Spitzer Legacy Program program and by a complementary optical survey. We also investigate the relationship between the proper motions (pm) and other properties, in order to get some clues about their formation and early evolution. Methods: We compiled a list of members and possible members of Lupus 1, 3, and 4, together with all information on their spectral types, disks, and physical parameters. Using VO-tools, we cross-matched this list with the astrometric catalogues to get pm. Our final sample contains sources with magnitudes I<16mag and estimated masses >~0.1Msun. Results: According to the kinematic information, our sources can be divided into two main groups. The first one contains sources with higher pm in agreement with other Gould Belt populations and with spatial distribution, optical and near-infrared colours, and disk composition consistent with these objects belonging to the Lupus clouds. In the second group, sources have lower pm with random orientations, and they are mostly located outside the cloud cores, making their association with the Lupus complex more doubtful. We investigate the properties of the higher pm group, but cannot find any correlations with spatial location, binarity, the presence of a circumstellar disk, or with physical properties such as effective temperature, luminosity, mass, or age. Conclusions: We conclude that the lower pm group probably represents a background population or mixture of populations unrelated to the Lupus clouds. The higher pm group, on the other hand, has properties consistent with it being a genuine population of the Lupus star-forming region. More accurate pm and/or radial velocity information are required for a more detailed study of the kinematic properties of the Lupus stellar members.

astro-ph.SR↗

arXiv2010

Two-resonator circuit QED: Dissipative Theory

We present a theoretical treatment for the dissipative two-resonator circuit quantum electrodynamics setup referred to as quantum switch. There, switchable coupling between two superconducting resonators is mediated by a superconducting qubit operating in the dispersive regime, where the qubit transition frequency is far detuned from those of the resonators. We derive an effective Hamiltonian for the quantum switch beyond the rotating wave approximation and study the dissipative dynamics within a Bloch-Redfield quantum master equation approach. We derive analytically how the qubit affects the quantum switch even if the qubit has no dynamics, and we estimate the strength of this influence. The analytical results are corroborated by numerical calculations, where coherent oscillations between the resonators, the decay of coherent and Fock states, and the decay of resonator-resonator entanglement are studied. Finally, we suggest an experimental protocol for extracting the damping constants of qubit and resonators by measuring the quadratures of the resonator fields.

cond-mat.supr-con↗

arXiv2009

Constrained optimization of sequentially generated entangled multiqubit states

We demonstrate how the matrix-product state formalism provides a flexible structure to solve the constrained optimization problem associated with the sequential generation of entangled multiqubit states under experimental restrictions. We consider a realistic scenario in which an ancillary system with a limited number of levels performs restricted sequential interactions with qubits in a row. The proposed method relies on a suitable local optimization procedure, yielding an efficient recipe for the realistic and approximate sequential generation of any entangled multiqubit state. We give paradigmatic examples that may be of interest for theoretical and experimental developments.

quant-ph↗

arXiv2009

Two-dimensional cavity grid for scalable quantum computation with superconducting circuits

Superconducting circuits are among the leading contenders for quantum information processing. This promising avenue has been strengthened with the advent of circuit quantum electrodynamics, underlined by recent experiments coupling on-chip microwave resonators to superconducting qubits. However, moving towards more qubits will require suitable novel architectures. Here, we propose a scalable setup for quantum computing where such resonators are arranged in a two-dimensional grid with a qubit at each intersection. Its versatility allows any two qubits on the grid to be coupled at a swapping overhead independent of their distance and yields an optimal balance between reducing qubit transition frequency spread and spurious cavity-induced couplings. These features make this setup unique and distinct from existing proposals in ion traps, optical lattices, or semiconductor spins. We demonstrate that this approach encompasses the fundamental elements of a scalable fault-tolerant quantum computing architecture.

cond-mat.mes-hall↗

arXiv2008

Quantum Zeno Effect in the Quantum Non-Demolition Detection of Itinerant Photons

We analyze the detection of itinerant photons using a quantum non-demolition (QND) measurement. We show that the backaction due to the continuous measurement imposes a limit on the detector efficiency in such a scheme. We illustrate this using a setup where signal photons have to enter a cavity in order to be detected dispersively. In this approach, the measurement signal is the phase shift imparted to an intense beam passing through a second cavity mode. The restrictions on the fidelity are a consequence of the Quantum Zeno effect, and we discuss both analytical results and quantum trajectory simulations of the measurement process.

cond-mat.mes-hall↗

arXiv2008

Monitoring atom-atom entanglement and decoherence in a solvable tripartite open system in cavity QED

We present a fully analytical solution of the dynamics of two strongly-driven atoms resonantly coupled to a dissipative cavity field mode. We show that an initial atom-atom entanglement cannot be increased. In fact, the atomic Hilbert space divides into two subspaces, one of which is decoherence free so that the initial atomic entanglement remains available for applications, even in presence of a low enough atomic decay rate. In the other subspace a measure of entanglement, decoherence, and also purity, are described by a similar functional behavior that can be monitored by joint atomic measurements. Furthermore, we show the possible generation of Schrödinger-cat-like states for the whole system in the transient regime, as well as of entanglement for the cavity field and the atom-atom subsystems conditioned by measurements on the complementary subsystem.

quant-ph↗

arXiv2008

Quantum simulation of Anderson and Kondo lattices with superconducting qubits

We introduce a mapping between a variety of superconducting circuits and a family of Hamiltonians describing localized magnetic impurities interacting with conduction bands. This includes the Anderson model, the single impurity one- and two-channel Kondo problem, as well as the 1D Kondo lattice. We compare the requirements for performing quantum simulations using the proposed circuits to those of universal quantum computation with superconducting qubits, singling out the specific challenges that will have to be addressed.

cond-mat.mes-hall↗

arXiv2007

Theoretical models in the Virtual Observatory

Although full interoperativity between theoretical and observational data in the framework of the Virtual Observatory would be a very desirable achievement, the current status of VO offers few approaches to handle theoretical models. TSAP (Theoretical Spectra Access Protocol) has been proposed as a tool to fill this void, providing a simple scheme to easily operate with th is kind of data. TSAP is useful not only for synthetic spectra but also for other types of theoretical data. As an example we show an Isochrone and Evolutionary Tracks server using TSAP. Finally, we pay special attention to the correct treatment of the credits an important issue in the field of theoretical models.

astro-ph↗

arXiv2007

Albus 1: A very bright white dwarf candidate

We have serendipitously discovered a previously-unknown, bright source (B_T = 11.75+/-0.07 mag) with a very blue V_T-K_s color, to which we have named Albus 1. A photometric and astrometric study using Virtual Observatory tools has shown that it possesses an appreciable proper motion and magnitudes and colors very similar to those of the well known white dwarf G 191-B2B. We consider Albus 1 as a DA-type white dwarf located at about 40 pc. If confirmed its nature, Albus 1 would be the sixth brightest isolated white dwarf in the sky, which would make it an excellent spectrophotometric standard.

astro-ph↗

arXiv2006

Experimental Observation of Four-Photon Entangled Dicke State with High Fidelity

We present the experimental observation of the symmetric four-photon entangled Dicke state with two excitations $|D_{4}^{(2)}>$. A simple experimental set-up allowed quantum state tomography yielding a fidelity as high as $0.844 \pm 0.008$. We study the entanglement persistency of the state using novel witness operators and focus on the demonstration of a remarkable property: depending on the orientation of a measurement on one photon, the remaining three photons are projected into both inequivalent classes of genuine tripartite entanglement, the GHZ and W class. Furthermore, we discuss possible applications of $|D_{4}^{(2)}>$ in quantum communication.

quant-ph↗

arXiv2002

One-atom maser: Non-separable atom pairs

When a one-atom maser is operated in the standard way -- excited, resonant two-level atoms traverse the resonator at random times -- the emerging atoms are entangled with the cavity field. As a consequence, the results of measurements on different atoms tend to be correlated. We show that truly non-classical correlations can be found between two successive atoms by studying the properties of the reduced state of such an atom pair. In particular, we calculate its degree of separability and find parameter ranges in which it is markedly less than unity.

quant-ph↗

arXiv2002

Generation and degree of entanglement in a relativistic formulation

The generation of entangled states and their degree of entanglement is studied ab initio in a relativistic formulation for the case of two interacting spin-1/2 charged particles. In the realm of quantum electrodynamics we derive the interaction that produces entanglement between the spin components of covariant Dirac spinors describing the two particles. Following this consistent approach the relativistic invariance of the generated entanglement is discussed.

quant-ph↗