arXiv subjects

Andrey L. Pankratov

Publications and source records attributed to Andrey L. Pankratov.

17 recordsLinked to original sources

arXiv2025

Search for dark-matter axions beyond the quantum limit: the Cosmological Axion Sarov Haloscope (CASH) proposal

Firmly established in astrophysical observations, dark matter evades direct detection in experiments. Axions and axion-like particles are among the leading dark-matter candidates, and numerous attempts to detect them in laboratories have been performed. Here, we propose to advance these efforts substantially, extending the sensitivity for dark-matter axions in the mass range $(38-54)~μ$eV down to the axion-photon couplings $g_{aγγ}\lesssim \left(10^{-14}-10^{-15}\right)$ GeV$^{-1}$, motivated by generic models of Quantum Chromodynamics axion. Single-photon detectors operating at ultra-low temperatures are key elements of the experiment. The projected sensitivity will be reached in one year of data taking with magnetic field of $(1-10)$ T, making Cosmological Axion Sarov Haloscope (CASH) the most sensitive haloscope in this mass range.

hep-ph↗

arXiv2025

Josephson microwave photon detector operating at 0.7 K

We predict that the threshold detectors based on Al Josephson junctions, with critical currents below 100 nA, exhibiting a phase diffusion regime, can be exploited for the microwave photon detection both at 17 mK and 700 mK. We demonstrate a detection of two- and one-photon energies at 5 GHz with 90% and 15% efficiency and dark count time of about 0.1 s and 0.01 s, respectively. The observed weak temperature dependence of the detector's performance in the sub-kelvin range fully confirms its phase-diffusion mode of operation. On the other hand, these results show that inevitable thermal fluctuations are not the main source of the detector noise. Consequently, there is still a room to optimize the detector's performance. These results are important for axion search experiments in the range of 5-25 GHz (20-100 $μ$eV).

cond-mat.dis-nn↗

arXiv2015

Soliton scattering as a measurement tool for weak signals

We have considered relativistic soliton dynamics governed by the sine-Gordon equation and affected by short spatial inhomogeneities of the driving force and thermal noise. Developed analytical and numerical methods for calculation of soliton scattering at the inhomogeneities allowed us to examine the scattering as a measurement tool for sensitive detection of polarity of the inhomogeneities. We have considered the superconducting fluxonic ballistic detector as an example of the device in which the soliton scattering is utilized for quantum measurements of superconducting flux qubit. We optimized the soliton dynamics for the measurement process varying the starting and the stationary soliton velocity as well as configuration of the inhomogeneities. For experimentally relevant parameters we obtained the signal-to-noise ratio above 100 reflecting good practical usability of the measurement concept.

cond-mat.supr-con↗

arXiv2011

Drastically suppressing the error of ballistic readout of qubits

The thermal jitter of transmission of magnetic flux quanta in long Josephson junctions is studied. While for large-to-critical damping and small values of bias current the physically obvious dependence of the jitter versus length $σ\sim\sqrt{L}$ is confirmed, for small damping starting from the experimentally relevant $α=0.03$ and below strong deviation from $σ\sim\sqrt{L}$ is observed, up to nearly complete independence of the jitter versus length, which is exciting from fundamental point of view, but also intriguing from the point of view of possible applications.

cond-mat.supr-con↗

arXiv2011

Influence of the Josephson junction geometry on the spectral properties of the flux-flow oscillator

Numerical investigation of the effects of junction geometry on the performance of the flux-flow type Josephson oscillator has been done. Using direct simulation of the sine-Gordon equation with account of RC load the spectral and power properties for different current density distributions have been calculated. With discussion of the fundamental differences in the dynamics of the inline and overlap junctions the various behavior depending on the junction length and noise intensity has been shown.

cond-mat.supr-con↗

arXiv2010

Fine tuning of phase qubit parameters for optimization of fast single-pulse readout

We analyze a two-level quantum system, describing the phase qubit, during a single-pulse readout process by a numerical solution of the time-dependent Schroedinger equation. It has been demonstrated that the readout error has a minimum for certain values of the system`s basic parameters. In particular, the optimization of the qubit capacitance and the readout pulse shape leads to significant reduction of the readout error. It is shown that in an ideal case the fidelity can be increased to almost 97% for 2 ns pulse duration and to 96% for 1 ns pulse duration.

cond-mat.mes-hall↗

arXiv2009

Optimal fast single pulse readout of qubits

The computer simulations of the process of single pulse readout from the flux-biased phase qubit is performed in the frame of one-dimensional Schroedinger equation. It has been demonstrated that the readout error can be minimized by choosing the optimal pulse duration and the depth of a potential well, leading to the fidelity of 0.94 for 2ns and 0.965 for 12ns sinusoidal pulses.

quant-ph↗

arXiv2008

Lifetime of the superconductive state in short and long Josephson junctions

We study the transient statistical properties of short and long Josephson junctions under the influence of thermal and correlated fluctuations. In particular, we investigate the lifetime of the superconductive metastable state finding the presence of noise induced phenomena. For short Josephson junctions we investigate the lifetime as a function both of the frequency of the current driving signal and the noise intensity and we find how these noise-induced effects are modified by the presence of a correlated noise source. For long Josephson junctions we integrate numerically the sine-Gordon equation calculating the lifetime as a function of the length of the junction both for inhomogeneous and homogeneous bias current distributions. We obtain a nonmonotonic behavior of the lifetime as a function of the frequency of the current driving signal and the correlation time of the noise. Moreover we find two maxima in the nonmonotonic behaviour of the mean escape time as a function of the correlated noise intensity.

cond-mat.supr-con↗

arXiv2008

Noise induced phenomena in point Josephson junctions

We present the analysis of the mean switching time and its standard deviation of short overdamped Josephson junctions, driven by a direct current and a periodic signal. The effect of noise enhanced stability is investigated. It is shown that fluctuations may both decrease and increase the switching time.

cond-mat.supr-con↗

arXiv2005

Noise suppression in transmission of single flux quantum signals

We present the analysis of the mean switching time and its standard deviation of an overdamped Josephson junction, driven by a direct current and a single flux quantum (SFQ) pulse. The performed analysis allows to find the optimal value of the bias current of the clock generator, responsible for the shape of SFQ pulse, which minimizes noise-induced switching errors.

cond-mat.supr-con↗

arXiv2004

Suppression of timing errors in short overdamped Josephson junctions

The influence of fluctuations and periodical driving on temporal characteristics of short overdamped Josephson junction is analyzed. We obtain the standard deviation of the switching time in the presence of a dichotomous driving force for arbitrary noise intensity and in the frequency range of practical interest. For sinusoidal driving the resonant activation effect has been observed. The mean switching time and its standard deviation have a minimum as a function of driving frequency. As a consequence the optimization of the system for fast operation will simultaneously lead to minimization of timing errors.

cond-mat.stat-mech↗

arXiv2002

Optimal Pump Frequency for Ac Hysteretic Squid

This paper presents the analytical and numerical analysis of fluctuational dynamics of ac hysteretic SQUID. It has been demonstrated, that the most important parameter for the improvement of the hysteretic SQUID sensitivity is the ratio between the pump and the characteristic frequencies but not their absolute values. The resonant behavior of signal-to-noise ratio as function of the pump frequency has been observed and the narrow area for the optimal pump frequency range is indicated.

cond-mat.supr-con↗

arXiv2002

Long Josephson junctions with spatially inhomogeneous driving

The phase dynamics of a long Josephson junction with spatially inhomogeneously distributed bias current is considered for the case of a dense soliton chain (regime of the Flux Flow oscillator). To derive the analytical solution of the corresponding sine-Gordon equation the Poincare method has been used. In the range of the validity of the theory good coincidence between analytically derived and numerically computed current-voltage characteristics have been demonstrated for the simplest example of unitstep function distribution of bias current (unbiased tail). It is shown, that for the considered example of bias current distribution, there is an optimal length of unbiased tail that maximizes the amplitude of the main harmonic and minimizes the dynamical resistance (thus leading to reduction of a linewidth).

cond-mat.supr-con↗

arXiv2001

Form and width of spectral line of Josephson Flux-Flow oscillator

The behavior of a Josephson flux-flow oscillator in the presence of both bias current and magnetic field fluctuations has been studied. To derive the equation for slow phase dynamics in the limit of small noise intensity the Poincare method has been used. Both the form of spectral line and the linewidth of the flux-flow oscillator have been derived exactly on the basis of technique presented in the book of Malakhov, known limiting cases are considered, limits of their applicability are discussed and appearance of excess noise is explained. Good coincidence of theoretical description with experimental results has been demonstrated.

cond-mat.supr-con↗

arXiv2001

Suprathreshold stochastic resonance: suppression of noise by strong periodic signals

We consider an overdamped Brownian motion in "quartic" potential subjected to periodic driving. This system for the case of a weak periodic driving has been intensively studied during past decade within the context of stochastic resonance. We had demonstrated, that for the case of predominantly suprathreshold driving the noise in the output signal is strongly suppressed at certain frequency range: the signal-to-noise ratio demonstrates resonant behavior as function of frequency.

cond-mat.dis-nn↗

arXiv1999

Nondecay probability of a metastable state: almost exact analytical description in wide range of noise intensity

This paper presents a complete description of noise-induced decay of a metastable state in a wide range of noise intensity. Recurrent formulas of exact moments of decay time valid for arbitrary noise intensity have been obtained. The nondecay probability of a metastable state was found to be really close to the exponent even for the case when the potential barrier height is comparable or smaller than the noise intensity.

adap-org↗

arXiv1998

Time evolution of averages in dynamical systems driven by noise

This paper presents description of time evolution of averages of Markov process in wide range of noise intensity. Exact expression of time scale of average evolution has been obtained. It has been demonstrated numerically that for purely noise-induced transitions (transitions over potential barriers) the time evolution of mean coordinate is a simple exponent with a good precision even for the case when the potential barrier height is comparable or smaller than the noise intensity. Also it has been demonstrated that nonlinear system may be "linearized" by a strong noise.

adap-org↗