arXiv subjects

A. N. Korotkov

Publications and source records attributed to A. N. Korotkov.

29 records · Page 2Linked to original sources

arXiv2006

Theory of measurement crosstalk in superconducting phase qubits

We analyze the crosstalk error mechanism in measurement of two capacitively coupled superconducting flux-biased phase qubits. The damped oscillations of the superconducting phase after the measurement of the first qubit may significantly excite the second qubit, leading to its measurement error. The first qubit, which is highly excited after the measurement, is described classically. The second qubit is treated both classically and quantum-mechanically. The results of the analysis are used to find the upper limit for the coupling capacitance (thus limiting the frequency of two-qubit operations) for a given tolerable value of the measurement error probability.

cond-mat.supr-con↗

arXiv2006

A Numerical Study of Transport and Shot Noise at 2D Hopping

We have used modern supercomputer facilities to carry out extensive Monte Carlo simulations of 2D hopping (at negligible Coulomb interaction) in conductors with the completely random distribution of localized sites in both space and energy, within a broad range of the applied electric field $E$ and temperature $T$, both within and beyond the variable-range hopping region. The calculated properties include not only dc current and statistics of localized site occupation and hop lengths, but also the current fluctuation spectrum. Within the calculation accuracy, the model does not exhibit $1/f$ noise, so that the low-frequency noise at low temperatures may be characterized by the Fano factor $F$. For sufficiently large samples, $F$ scales with conductor length $L$ as $(L_c/L)^α$, where $α=0.76\pm 0.08 < 1$, and parameter $L_c$ is interpreted as the average percolation cluster length. At relatively low $E$, the electric field dependence of parameter $L_c$ is compatible with the law $L_c\propto E^{-0.911}$ which follows from directed percolation theory arguments.

cond-mat.mes-hall↗

arXiv2000

Continuous weak measurement of quantum coherent oscillations

We consider the problem of continuous quantum measurement of coherent oscillations between two quantum states of an individual two-state system. It is shown that the interplay between the information acquisition and the backaction dephasing of the oscillations by the detector imposes a fundamental limit, equal to 4, on the signal-to-noise ratio of the measurement. The limit is universal, e.g., independent of the coupling strength between the detector and system, and results from the tendency of quantum measurement to localize the system in one of the measured eigenstates.

cond-mat.mes-hall↗

arXiv1998

Shot noise suppression in multimode ballistic Fermi conductors

We have derived a general formula describing current noise in multimode ballistic channels connecting source and drain electrodes with Fermi electron gas. In particular (at $eV\gg k_{B}T$), the expression describes the nonequilibrium ''shot'' noise, which may be suppressed by both Fermi correlations and space charge screening. The general formula has been applied to an approximate model of a 2D nanoscale, ballistic MOSFET. At large negative gate voltages, when the density of electrons in the channel is small, shot noise spectral density $S_{I}(0)$ approaches the Schottky value $2eI$, where $I$ is the average current. However, at positive gate voltages, when the maximum potential energy in the channel is below the Fermi level of the electron source, the noise can be at least an order of magnitude smaller than the Schottky value, mostly due to Fermi effects.

cond-mat.mes-hall↗

arXiv1998

Gain Dependence of the Noise in the Single Electron Transistor

An extensive investigation of low frequency noise in single electron transistors as a function of gain is presented. Comparing the output noise with gain for a large number of bias points, it is found that the noise is dominated by external charge noise. For low gains we find an additional noise contribution which is compared to a model including resistance fluctuations. We conclude that this excess noise is not only due to resistance fluctuations. For one sample, we find a record low minimum charge noise of qn = 9*10^-6 e/sqrt(Hz) in the superconducting state and qn = 9*10^-6 e/sqrt(Hz) in the normal state at a frequency of 4.4 kHz.

cond-mat.mes-hall↗

arXiv1998

Single-electron-parametron-based logic devices

We analyze the operation of the wireless single-electron logic family based on single-electron-parametron cells. Parameter margins, energy dissipation, and the error probability are calculated using the orthodox theory of single-electron tunneling. Circuits of this family enable quasi-reversible computation with energy dissipation per bit much lower than the thermal energy, and hence may circumvent one of the main obstacles faced by ultradense three-dimensional integrated digital circuits.

cond-mat.mes-hall↗

arXiv1998

Theoretical analysis of the resistively-coupled single-electron transistor

The operation of resistively-coupled single-electron transistor (R-SET) is studied quantitatively. Due to the Nyquist noise of the coupling resistance, degradation of the R-SET performance is considerable at temperatures $T$ as small as $10^{-3} e^2/C$ (where $C$ is the junction capacitance) while the voltage gain becomes impossible at $T\agt 10^{-2}e^2/C$.

cond-mat.mes-hall↗

arXiv1997

Noise in single quantum well infrared photodetectors

The spectral density of current fluctuations in single quantum well infrared photodetectors is calculated using Langevin approach. The noise gain and the photocurrent gain are expressed in terms of basic transport parameters. Fluctuations of the incident photon flux are taken into account.

cond-mat.mes-hall↗

arXiv1997

Singularity-matching peaks in superconducting single-electron transistor

We report the experimental observation of the recently predicted peaks on the I-V curve of the superconducting single-electron transistor at relatively high temperatures. The peaks are due to the matching of singularities in the quasiparticle density of states in two electrodes of a tunnel junction. The energy shift due to Coulomb blockade provides the matching at finite voltage.

cond-mat.supr-con↗

arXiv1997

Room Temperature Molecular Single-Electron Transistor

A room temperature single-electron transistor based on the single cluster molecule has been demonstrated for the first time. Scanning tunneling microscope tip was used to study the transport via single carboran cluster molecule 1,7-(CH_3)_2-1,2-C_2B_{10}H_9Tl(OCOCF_3)_2 incorporated into the Langmuir-Blodgett monolayer of the stearic acid. DC I-V curves at 300 K showed well pronounced Coulomb staircase, and the current could be controlled by a lithographically fabricated gold gate electrode.

cond-mat↗

arXiv1997

Resonant tunneling through a macroscopic charge state in a superconducting SET transistor

We predict theoretically and observe in experiment that the differential conductance of a superconducting SET transistor exhibits a peak which is a complete analogue in a macroscopic system of a standard resonant tunneling peak associated with tunneling through a single quantum state. In particular, in a symmetric transistor, the peak height is universal and equal to $e^2/2π\hbar$. Away from the resonance we clearly observe the co-tunneling current which in contrast to the normal-metal transistor varies linearly with the bias voltage.

cond-mat.mes-hall↗