Adiabatic response and quantum thermoelectrics for ac driven quantum systems

We generalize the theory of thermoelectrics to include coherent electron systems under adiabatic ac driving, accounting for quantum pumping of charge and heat as well as the associated work exchange between electron system and driving potentials. We derive the relevant response coefficients in the adiabatic regime and show that they obey Onsager reciprocity relations. We analyze the consequences of our generalized thermoelectric framework for quantum motors, generators, heat engines, and heat pumps, characterizing them in terms of efficiencies and figures of merit.Comment: Published versio

Transport and optical response of molecular junctions driven by surface plasmon-polaritons

We consider a biased molecular junction subjected to external time-dependent electromagnetic field. The field for two typical junction geometries (bowtie antennas and metal nanospheres) is calculated within finite-difference time-domain technique. Time-dependent transport and optical response of the junctions is calculated within non-equilibrium Green's function approach expressed in a form convenient for description of multi-level systems. We present numerical results for a two-level (HOMO-LUMO) model, and discuss influence of localized surface plasmon polariton modes on transport.Comment: 9 pages, 6 figure

Engineering Gaussian states of light from a planar microcavity

Quantum fluids of light in a nonlinear planar microcavity can exhibit antibunched photon statistics at short distances due to repulsive polariton interactions. We show that, despite the weakness of the nonlinearity, the antibunching signal can be amplified orders of magnitude with an appropriate free-space optics scheme to select and interfere output modes. Our results are understood from the unconventional photon blockade perspective by analyzing the approximate Gaussian output state of the microcavity. In a second part, we illustrate how the temporal and spatial profile of the density-density correlation function of a fluid of light can be reconstructed with free-space optics. Also here the nontrivial (anti)bunching signal can be amplified significantly by shaping the light emitted by the microcavity

Josephson parametric reflection amplifier with integrated directionality

A directional superconducting parametric amplifier in the GHz frequency range is designed and analyzed, suitable for low-power read-out of microwave kinetic inductance detectors employed in astrophysics and when combined with a nonreciprocal device at its input also for circuit quantum electrodynamics (cQED). It consists of an one wavelength long nondegenerate Josephson parametric reflection amplifier circuit. The device has two Josephson junction oscillators, connected via a tailored impedance to an on-chip passive circuit which directs the in- to the output port. The amplifier provides a gain of 20 dB over a bandwidth of 220 MHz on the signal as well as on the idler portion of the amplified input and the total photon shot noise referred to the input corresponds to maximally 1.3 photons per second per Hertz of bandwidth. We predict a factor of four increase in dynamic range compared to conventional Josephson parametric amplifiers.Comment: Main article (5 pages plus 2 pages references) plus supplemental material (14 pages

Experiments with a Convex Polyhedral Analysis Tool for Logic Programs

Convex polyhedral abstractions of logic programs have been found very useful in deriving numeric relationships between program arguments in order to prove program properties and in other areas such as termination and complexity analysis. We present a tool for constructing polyhedral analyses of (constraint) logic programs. The aim of the tool is to make available, with a convenient interface, state-of-the-art techniques for polyhedral analysis such as delayed widening, narrowing, "widening up-to", and enhanced automatic selection of widening points. The tool is accessible on the web, permits user programs to be uploaded and analysed, and is integrated with related program transformations such as size abstractions and query-answer transformation. We then report some experiments using the tool, showing how it can be conveniently used to analyse transition systems arising from models of embedded systems, and an emulator for a PIC microcontroller which is used for example in wearable computing systems. We discuss issues including scalability, tradeoffs of precision and computation time, and other program transformations that can enhance the results of analysis.Comment: Paper presented at the 17th Workshop on Logic-based Methods in Programming Environments (WLPE2007