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Search Results: 1 - 10 of 443 matches for " Borja Peropadre "
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Light-matter decoupling and $A^2$ term detection in superconducting circuits
Juan José García-Ripoll,Borja Peropadre,Simone De Liberato
Physics , 2014, DOI: 10.1038/srep16055
Abstract: We study the spontaneous emission of a qubit interacting with a one-dimensional waveguide through a realistic minimal-coupling interaction. We show that the diamagnetic term $A^2$ leads to an effective decoupling of a single qubit from the electromagnetic field. This effects is observable at any range of qubit-photon couplings. For this we study a setup consisting of a transmon that is suspended over a transmission line. We prove that the relative strength of the $A^2$ term is controlled with the qubit-line separation and show that, as a consequence, the spontaneous emission rate of the suspended transmon onto the line can increase with such separation, instead of decreasing.
Boson Sampling for Molecular Vibronic Spectra
Joonsuk Huh,Gian Giacomo Guerreschi,Borja Peropadre,Jarrod R. McClean,Alán Aspuru-Guzik
Physics , 2014, DOI: 10.1038/nphoton.2015.153
Abstract: Quantum computers are expected to be more efficient in performing certain computations than any classical machine. Unfortunately, the technological challenges associated with building a full-scale quantum computer have not yet allowed the experimental verification of such an expectation. Recently, boson sampling has emerged as a problem that is suspected to be intractable on any classical computer, but efficiently implementable with a linear quantum optical setup. Therefore, boson sampling may offer an experimentally realizable challenge to the Extended Church-Turing thesis and this remarkable possibility motivated much of the interest around boson sampling, at least in relation to complexity-theoretic questions. In this work, we show that the successful development of a boson sampling apparatus would not only answer such inquiries, but also yield a practical tool for difficult molecular computations. Specifically, we show that a boson sampling device with a modified input state can be used to generate molecular vibronic spectra, including complicated effects such as Duschinsky rotations.
Quantum nonlinear optics with polar J-aggregates in microcavities
Felipe Herrera,Borja Peropadre,Leonardo A. Pachon,Semion K. Saikin,Alán Aspuru-Guzik
Physics , 2014, DOI: 10.1021/jz501905h
Abstract: We show that an ensemble of organic dye molecules with permanent electric dipole moments embedded in a microcavity can lead to strong optical nonlinearities at the single photon level. The strong long-range electrostatic interaction between chromophores due to their permanent dipoles introduces the desired nonlinearity of the light-matter coupling in the microcavity. We obtain the absorption spectra of a weak probe field under the influence of strong exciton-photon coupling with the cavity field. Using realistic parameters, we demonstrate that a single cavity photon can significantly modify the absorptive and dispersive response of the medium to a probe photon at a different frequency. Finally, we show that the system is in the regime of cavity-induced transparency with a broad transparency window for dye dimers. We illustrate our findings using pseudoisocyanine chloride (PIC) J-aggregates in currently-available optical microcavities.
The Single-Photon Router
Io-Chun Hoi,C. M. Wilson,G?ran Johansson,Tauno Palomaki,Borja Peropadre,Per Delsing
Physics , 2011, DOI: 10.1103/PhysRevLett.107.073601
Abstract: We have embedded an artificial atom, a superconducting "transmon" qubit, in an open transmission line and investigated the strong scattering of incident microwave photons ($\sim6$ GHz). When an input coherent state, with an average photon number $N\ll1$ is on resonance with the artificial atom, we observe extinction of up to 90% in the forward propagating field. We use two-tone spectroscopy to study scattering from excited states and we observe electromagnetically induced transparency (EIT). We then use EIT to make a single-photon router, where we can control to what output port an incoming signal is delivered. The maximum on-off ratio is around 90% with a rise and fall time on the order of nanoseconds, consistent with theoretical expectations. The router can easily be extended to have multiple output ports and it can be viewed as a rudimentary quantum node, an important step towards building quantum information networks.
Extracting past-future vacuum correlations using circuit QED
Carlos Sabin,Borja Peropadre,Marco del Rey,Eduardo Martin-Martinez
Physics , 2012, DOI: 10.1103/PhysRevLett.109.033602
Abstract: We propose a realistic circuit QED experiment to test the extraction of past-future vacuum entanglement to a pair of superconducting qubits. The qubit P interacts with the quantum field along an open transmission line for an interval T_on and then, after a time-lapse T_off, the qubit F starts interacting for a time T_on in a symmetric fashion. After that, past-future quantum correlations will have transferred to the qubits, even if the qubits do not coexist at the same time. We show that this experiment can be realized with current technology and discuss its utility as a possible implementation of a quantum memory.
Spin models and boson sampling
Borja Peropadre,Alan Aspuru-Guzik,Juan Jose Garcia-Ripoll
Physics , 2015,
Abstract: In this work we proof that boson sampling with $N$ particles in $M$ modes is equivalent to short-time evolution with $N$ excitations in an XY model of $2N$ spins. This mapping is efficient whenever the boson bunching probability is small, and errors can be efficiently postselected. This mapping opens the door to boson sampling with quantum simulators or general purpose quantum computers, and highlights the complexity of time-evolution with critical spin models, even for very short times.
Microwave Quantum Optics with an Artificial Atom
Io-Chun Hoi,C. M. Wilson,G?ran Johansson,Joel Lindkvist,Borja Peropadre,Tauno Palomaki,Per Delsing
Physics , 2012, DOI: 10.1088/1367-2630/15/2/025011
Abstract: We address the recent advances on microwave quantum optics with artificial atoms. This field relies on the fact that the coupling between a superconducting artificial atom and propagating microwave photons in a 1D open transmission line can be made strong enough to observe quantum coherent effects, without using any cavity to confine the microwave photons. We investigate the scattering properties in such a system with resonant coherent microwaves. We observe the strong nonlinearity of the artificial atom and under strong driving we observe the Mollow triplet. By applying two resonant tones, we also observe the Autler-Townes splitting. By exploiting these effects, we demonstrate two quantum devices at the single-photon level in the microwave regime: the single-photon router and the photon-number filter. These devices provide essential steps towards the realization of an on-chip quantum network.
Facing a Shift in Paradigm at the Bedside?  [PDF]
Borja Vargas, Manuel Varela
International Journal of Clinical Medicine (IJCM) , 2013, DOI: 10.4236/ijcm.2013.41008
Abstract:

Our entire medical framework is based on the concept of disease, understood as a qualitative departure from normality (health) with a structural substrate (lesion), and usually an identifiable cause (aetiology). This paradigm is loaded with problems, some of which are discussed in the text. Nevertheless, we study, diagnose and treat diseases, and while often painfully conscious of the dysfunctionalities of this scheme, we can hardly imagine how we could practice medicine otherwise. However, most of the recent developments in basic sciences, and most notably in Immunology, Genetics and -omics, are inconsistent with this “health/disease” paradigm. The emerging scenario is that of complex networks, more in the spirit of Systems Biology. In these settings the qualitative difference between health and disease loses its meaning, and the whole discourse becomes progressively irreducible to our conventional clinical categories. As clinical research stagnates while basic sciences thrive, this gap is widening, and a change in the prevailing paradigm seems unavoidable. However, all our clinical judgments (including Bayesian reasoning and Evidence Based Medicine) are rooted in the disease/health dichotomy, and one can hardly conceive how they could work without it. The shift in paradigm will not be easy, and certain turmoil is to be expected.

Revolución y contrarrevolución en la ciudad global: las expectativas frustradas por la globalización de nuestras ciudades
Borja,Jordi;
EURE (Santiago) , 2007, DOI: 10.4067/S0250-71612007000300003
Abstract: a pessimistic analysis, even catastrophic, prevails in studies of global urbanization. for example, the reports of the undp-habitat or the worldwatch institute, or the articles and presentations in intellectual fora. this does not mean that the transformative and integrative potential of cities is not recognized. the positive discourse about citizens' liberties that the urban revolution, currently in process, makes possible forms part of our culture. these are the two sides of this reality. many cities, european and american, have promoted regeneration of their central areas that, in many cases, deal with almost an entire municipality, with a revaluing of the compact, heterogenous city characterized by the quality of public space. however the urban developments, the metropolitan regions, multiply inequalities over the landscape, generating spaces that are physically fragmented and socially segregated. the current urban revolution is frustrating. the political, urbanistic and cultural challenge today is to 'make the city' in all regions characterized by urbanization
Los caminos de la guerra durante el siglo XIX
Borja,Miguel;
Análisis Político , 2009,
Abstract: using travelers' diaries and documents from the period as sources, the article presents the main war roads during the xixth century. it emphasizes in their role as battle theaters and sources of economic and social capital. in an agrarian society as that of the xixth century, roads represented territorial stri pes of geostrategic importance for battles. political power sources and war spaces were located near such roads. in a time when war was mainly a war of positions, roads bordered not only economic structures, but also the geography of war. special attention is given to the roads crossing the region of valle and ca?ón del cauca delimited by popayán's high prairies and batolito antioque?o. the aforementioned region became a space containing warlike processes: not only one of the most progressive economies of the nation was located there but also a war geohistoric space crisscrossed by a set of roads that facilitated the movement of armed actors through all of the national territory.
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