Energy (signal processing)

About: Energy (signal processing) is a research topic. Over the lifetime, 26711 publications have been published within this topic receiving 613173 citations.

Quantum charge fluctuations of a proximitized nanowire

Abstract: Motivated by a recent experiment [Nature (London) 531, 206 (2016)], we consider charging of a nanowire which is proximitized by a superconductor and connected to a normal-state lead by a single-channel junction. The charge $Q$ of the nanowire is controlled by gate voltage $e{\mathcal{N}}_{g}/C$. A finite conductance of the contact allows for quantum charge fluctuations, making the function $Q({\mathcal{N}}_{g})$ continuous. It depends on the relation between the superconducting gap $\mathrm{\ensuremath{\Delta}}$ and the effective charging energy ${E}_{C}^{*}$. The latter is determined by the junction conductance in addition to the geometrical capacitance of the proximitized nanowire. We investigate $Q({\mathcal{N}}_{g})$ at zero magnetic field $B$ and at fields exceeding the critical value ${B}_{c}$ corresponding to the topological phase transition [Phys. Rev. Lett. 105, 077001 (2010); Phys. Rev. Lett. 105, 177002 (2010)]. Unlike the case of $\mathrm{\ensuremath{\Delta}}=0$, the function $Q({\mathcal{N}}_{g})$ is analytic even in the limit of negligible level spacing in the nanowire. At $B=0$ and $\mathrm{\ensuremath{\Delta}}g{E}_{C}^{*}$, the maxima of $dQ/d{\mathcal{N}}_{g}$ are smeared by $2e$ fluctuations described by a single-channel ``charge Kondo'' physics, whereas the $B=0,\phantom{\rule{0.28em}{0ex}}\mathrm{\ensuremath{\Delta}}l{E}_{C}^{*}$ case is described by a crossover between the Kondo and the mixed-valence regimes of the Anderson impurity model. In the topological phase, $Q({\mathcal{N}}_{g})$ is an analytic function of the gate voltage with $e$-periodic steps. In the weak-tunneling limit, $dQ/d{\mathcal{N}}_{g}$ has peaks corresponding to Breit-Wigner resonances, whereas in the strong-tunneling limit (i.e., small reflection amplitude $r$) these resonances are broadened, and $dQ/d{\mathcal{N}}_{g}\ensuremath{-}e\ensuremath{\propto}r\phantom{\rule{0.16em}{0ex}}cos(2\ensuremath{\pi}{\mathcal{N}}_{g})$.

Insights Into the Operation of Hyper-FET-Based Circuits

Abstract: Devices combining transistors and phase transition materials are being investigated to obtain steep switching and a boost in the ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratio and, thus, to solve power and energy limitations of CMOS technologies. This paper analyzes the operation of circuits built with these devices. In particular, we use a recently projected device called hyper-FET to simulate different circuits, and to analyze the impact of the degraded dc output voltage levels of hyper-FET logic gates on their circuit operation. Experiments have been carried out to evaluate power of these circuits and to compare with counterpart circuits using FinFETs. The estimated power advantages from device level analysis are also compared with the results of circuit level measurements. We show that these estimations can reduce, cancel, or even lead to power penalties in low switching and/or low-frequency circuits. We also discuss relationships with some device level parameters showing that circuit level considerations should be taken into account for device design.

Global description of the Li 7 + p reaction at 5.44 MeV/u in a continuum-discretized coupled-channels approach

Abstract: The complete set of open channels for the $^{7}\mathrm{Li}+p$ system, namely elastic scattering, inelastic scattering, breakup, the $^{7}\mathrm{Li}+p\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{7}\mathrm{Be}+n$ charge exchange reaction, and the $^{7}\mathrm{Li}+p\phantom{\rule{4pt}{0ex}}\ensuremath{\rightarrow}\phantom{\rule{4pt}{0ex}}^{4}\mathrm{He}+^{4}\mathrm{He}$ reaction, was measured in the same experiment in inverse kinematics at an energy of 5.44 MeV/u. Data were also obtained for the charge exchange reaction at energies of 5.0 and 3.57 MeV/u. The elastic and inelastic scattering and breakup data were reported previously and are reviewed here and, together with the new data for the other two reactions, are discussed coherently within the same continuum-discretized coupled-channels model framework.

Epsilon-net method for optimizations over separable states

Abstract: We give algorithms for the optimization problem: $\max_\rho \ip{Q}{\rho}$, where $Q$ is a Hermitian matrix, and the variable $\rho$ is a bipartite {\em separable} quantum state. This problem lies at the heart of several problems in quantum computation and information, such as the complexity of QMA(2). While the problem is NP-hard, our algorithms are better than brute force for several instances of interest. In particular, they give PSPACE upper bounds on promise problems admitting a QMA(2) protocol in which the verifier performs only logarithmic number of elementary gate on both proofs, as well as the promise problem of deciding if a bipartite local Hamiltonian has large or small ground energy. For $Q\ge0$, our algorithm runs in time exponential in $\|Q\|_F$. While the existence of such an algorithm was first proved recently by Brand{\~a}o, Christandl and Yard [{\em Proceedings of the 43rd annual ACM Symposium on Theory of Computation}, 343--352, 2011], our algorithm is conceptually simpler.