arXiv subjects

Leonid S. Kuzmin

Publications and source records attributed to Leonid S. Kuzmin.

6 recordsLinked to original sources

arXiv2021

Single-photon detection with a Josephson junction coupled to a resonator

We use semiclassical formalism to optimize a microwave single photon detector based on switching events of a current biased Josephson junction coupled to a resonator. In order to detect very rare events, the average time between dark counts $τ_{\rm dark}$ should be maximized taking into account that the switching time $τ_{\rm sw}$ should be sufficiently small. We demonstrate that these times can be tuned in the wide range by changing the junction parameters, and the ratios $τ_{\rm dark}/τ_{\rm sw} \sim 10^9$ can be achieved. Therefore, a junction-resonator arrangement can be used for detecting extremely low photon fluxes, for instance for searching galactic axions.

cond-mat.supr-con↗

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↗

arXiv2014

Cold-electron bolometers for future mm and sub-mm sky surveys

Future sky surveys in the mm/sub-mm range, like the forthcoming balloon-borne missions LSPE, OLIMPO, SPIDER etc., will need detectors insensitive to cosmic rays (CRs) and with a NEP of the order of $10^{-17} ÷10^{-18}\,$W/sqrt(Hz). The Cold-Electron Bolometers (CEBs) technology is promising, having the required properties, since the absorber volume is extremely small and the electron system of the absorber is thermally insulated from the phonon system. We have developed an experimental setup to test the optical performance and the CRs insensitivity of CEBs, with the target of integrating them in the OLIMPO and LSPE focal planes.

astro-ph.IM↗

arXiv2012

Dephasing of Cooper pairs and subgap electron transport in superconducting hybrids

We argue that electron-electron interactions fundamentally restrict the penetration length of Cooper pairs into a diffusive normal metal (N) from a superconductor (S). At low temperatures this Cooper pair dephasing length $L_φ$ remains finite and does not diverge at $T \to 0$. We evaluate the subgap conductance of NS hybrids in the presence of electron-electron interactions and demonstrate that this new length $L_φ$ can be directly extracted from conductance measurements in such structures.

cond-mat.mes-hall↗

arXiv2012

Theory of a large thermoeffect in superconductors doped with magnetic impurities

We argue that parametrically strong enhancement of a thermoelectric current can be observed in conventional superconductors doped by magnetic impurities. This effect is caused by violation of the symmetry between electron-like and hole-like excitations due to formation of subgap Andreev bound states in the vicinity of magnetic impurities. We develop a quantitative theory of this effect and demonstrate that it can be detected in modern experiments.

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↗