Latest Papers in Condensed Matter Physics

Mesoscale And Nanoscale Physics

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Majorana finite frequency nonequilibrium quantum noise (1904.05827v1)

Sergey Smirnov

2019-04-11

Quantum finite frequency noise is one of fundamental aspects in quantum measurements performed during quantum information processing where currently Majorana bound states offer an efficient way to implement fault-tolerant quantum computation via topological protection from decoherence or unitary errors. Thus a detailed exploration of Majorana finite frequency noise spectra, preferably in a nonequilibrium device, is a timely challenge of fundamental importance. Here we present results on finite frequency differential noise that is the derivative of the noise with respect to the frequency. This quantity has universal units of and scans in high detail all peculiarities of the Majorana noise clearly demonstrating its universal finite frequency features. In particular, we provide photon absorption spectra on all energy scales and reveal a rich structure including universal Majorana plateaus as well as universal Majorana resonances and antiresonances at characteristic frequencies. Our results are of immediate interest to state-of-the-art experiments involving quantum noise mesoscopic detectors able to separately measure photon absorption and emission spectra.

Towards Prediction of Financial Crashes with a D-Wave Quantum Computer (1904.05808v1)

Yongcheng Ding, Lucas Lamata, Mikel Sanz, José D. Martín-Guerrero, Enrique Lizaso, Samuel Mugel, Xi Chen, Román Orús, Enrique Solano

2019-04-11

Prediction of financial crashes in a complex financial network is known to be an NP-hard problem, i.e., a problem which cannot be solved efficiently with a classical computer. We experimentally explore a novel approach to this problem by using a D-Wave quantum computer to obtain financial equilibrium more efficiently. To be specific, the equilibrium condition of a nonlinear financial model is embedded into a higher-order unconstrained binary optimization (HUBO) problem, which is then transformed to a spin- Hamiltonian with at most two-qubit interactions. The problem is thus equivalent to finding the ground state of an interacting spin Hamiltonian, which can be approximated with a quantum annealer. Our experiment paves the way to study quantitative macroeconomics, enlarging the number of problems that can be handled by current quantum computers.

Towards Pricing Financial Derivatives with an IBM Quantum Computer (1904.05803v1)

Ana Martin, Bruno Candelas, Ángel Rodríguez-Rozas, José D. Martín-Guerrero, Xi Chen, Lucas Lamata, Román Orús, Enrique Solano, Mikel Sanz

2019-04-11

Pricing interest-rate financial derivatives is a major problem in finance, in which it is crucial to accurately reproduce the time-evolution of interest rates. Several stochastic dynamics have been proposed in the literature to model either the instantaneous interest rate or the instantaneous forward rate. A successful approach to model the latter is the celebrated Heath-Jarrow-Morton framework, in which its dynamics is entirely specified by volatility factors. On its multifactor version, this model considers several noisy components to capture at best the dynamics of several time-maturing forward rates. However, as no general analytical solution is available, there is a trade-off between the number of noisy factors considered and the computational time to perform a numerical simulation. Here, we employ the quantum principal component analysis to reduce the number of noisy factors required to accurately simulate the time evolution of several time-maturing forward rates. The principal components are experimentally estimated with the -qubit IBMQX2 quantum computer for and cross-correlation matrices, which are based on historical data for two and three time-maturing forward rates. This manuscript is a first step towards the design of a general quantum algorithm to fully simulate on quantum computers the Heath-Jarrow-Morton model for pricing interest-rate financial derivatives. It shows indeed that practical applications of quantum computers in finance will be achievable in the near future.

Large-signal model of the Metal-Insulator-Graphene diode targeting RF applications (1904.05792v1)

Francisco Pasadas, Mohamed Saeed, Ahmed Hamed, Zhenxing Wang, Renato Negra, Daniel Neumaier, David Jiménez

2019-04-11

We present a circuit-design compatible large-signal compact model of metal-insulator-graphene (MIG) diodes for describing its dynamic response for the first time. The model essentially consists of a voltage-dependent diode intrinsic capacitance coupled with a static voltage-dependent current source, the latter accounts for the vertical electron transport from/towards graphene, which has been modeled by means of the Dirac-thermionic electron transport theory through the insulator barrier. Importantly, the image force effect has been found to play a key role in determining the barrier height, so it has been incorporated into the model accordingly. The resulting model has been implemented in Verilog A to be used in existing circuit simulators and benchmarked against an experimental 6-nm TiO2 barrier MIG diode working as a power detector.

Effect of charge renormalization on electric and thermo-electric transport along the vortex lattice of a Weyl superconductor (1904.05758v1)

G. Lemut, M. J. Pacholski, İ. Adagideli, C. W. J. Beenakker

2019-04-11

Building on the discovery that a Weyl superconductor in a magnetic field supports chiral Landau level motion along the vortex lines, we investigate its transport properties out of equilibrium. We show that the vortex lattice carries an electric current between two normal metal contacts at voltage difference , with the magnetic flux through the system, the superconducting flux quantum, and the renormalized charge of the Weyl fermions in the superconducting Landau level. Because the charge renormalization is energy dependent, a nonzero thermo-electric coefficient appears even in the absence of energy-dependent scattering processes.

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