arXiv subjects

Ekaterina Mukhanova

Publications and source records attributed to Ekaterina Mukhanova.

5 recordsLinked to original sources

arXiv2026

Performance optimization of cascaded traveling wave Josephson parametric amplifiers

Traveling-wave parametric amplifiers (TWPAs) based on Josephson metamaterials provide broadband gain with near-quantum-limited added noise. Whereas long nonlinear metamaterial devices can deliver high gain, short arrays suffer less from dissipation, pump depletion, and internal standing waves which can degrade noise performance. Here, we demonstrate a cascaded TWPA architecture that combines the advantages of both approaches by employing a short (736-element), low-dissipation Superconducting Nonlinear Asymmetric Inductive eLement (SNAIL)-based TWPA as the first amplification stage, followed by a conventional long (1632-element) TWPA that provides additional gain. The resulting amplifier cascade achieves nearly 30 dB of total gain over a tunable bandwidth of approximately 1 GHz while maintaining added noise close to the quantum limit. Our results establish a cascade of TWPAs as a practical approach for high-gain, broadband, quantum amplification with applications in quantum information processing, multi-mode entanglement, and quantum sensing applications at microwave frequencies.

quant-ph↗

arXiv2026

Phase-sensitive cascade quantum amplifier with nearly noiseless operation

Phase-sensitive parametric devices enable quadrature-selective amplification with the potential for sub-quantum-limited noise performance. In this work, we investigate the operation of a SQUID-based Josephson Parametric Amplifier (JPA), comparing its performance in the phase-preserving and phase-sensitive regimes. The device, fabricated using VTT SWAPS technology, is driven in a three-wave mixing configuration and characterized in a reflection-based measurement setup at millikelvin temperatures. To directly probe the noise performance at low JPA gains, we employ a cascaded amplification scheme in which a Traveling-Wave Parametric Amplifier (TWPA) provides low-noise pre-amplification of the JPA output. In a phase-preserving operation, the JPA exhibits near-quantum-limited performance with a system noise temperature of $351\pm53$ mK at 6 GHz. In contrast, phase-sensitive operation yields a minimum system noise temperature of $94\pm12$ mK, well below the standard quantum limit of 288 mK. Our results demonstrate that a JPA-TWPA amplifier cascade opens the door to direct, high-fidelity probing of quantum devices without the need for background noise subtraction.

quant-ph↗

arXiv2026

Bipartite entanglement under frequency comb pumping in parametric Josephson circuits

The creation of high-quality cluster states in superconducting microwave circuits is a relevant ingredient in continuous-variable quantum computing. Although large-scale cluster states have been established in optical systems, dissipation prevents their direct applicability to the microwave realm. Recent improvements in superconducting parametric circuits, in particular Josephson parametric amplifiers (JPA) and traveling wave parametric amplifiers (TWPA), have permitted substantial progress in producing entangled states using microwave photons. In this paper, we examine experimentally and theoretically the effects of numerous parametric pump tones on the degree of two-mode squeezing in a quantum circuit and apply it to the JPA. We find that additional pumps diminish the initial two-mode correlations achieved with a single pump by redistributing it among a larger network of modes and by introducing entanglement with additional idler frequencies. Taking into account the actual heterodyne measurement conditions, the experimental results are consistent with theoretical expectations.

quant-ph↗

arXiv2024

1/f frequency fluctuations due to kinetic inductance in CoSi$_2$ microwave cavities

Cobalt disilicide provides a promising nearly-epitaxial superconducting material on silicon, which is compatible with high-density integrated circuit technology. We have characterized CoSi$_{2}$ superconducting microwave cavities around 5.5 GHz for resonance frequency fluctuations at temperatures 10 - 200 mK. We found relatively weak fluctuations $(δf/f)^2$ following the spectral density $A/f^γ $, with $A \simeq 6 \times 10^{-16}$ and $γ$ slightly below 1 at an average number of photons of $10^4$; the noise decreased with measurement power as $1/P^{1/2}$. We identify the noise as arising from kinetic inductance fluctuations and discuss possible origins of such fluctuations.

cond-mat.supr-con↗

arXiv2023

Kinetic inductance in superconducting CoSi$_2$ coplanar microwave transmission lines

We have looked into cobalt disilicide (CoSi$_2$) as a potential building block for superconducting quantum circuits. In order to achieve this, we annealed a thin layer of Co to create 10-105 nm thick microwave cavities from CoSi$_2$ embedded in the silicon substrate. The cavity properties were measured as a function of temperature and power. In films measuring 10 and 25 nm, we find a significant kinetic inductance $L_\mathrm{K}$ with a non-BCS power-law variation $δL_\mathrm{K} \propto T^{4.3 \pm 0.2}$ at low temperatures. The quality factor of the studied microwave resonances increased almost linearly with thickness, with two-level systems having very little effect. The power dependence of kinetic inductance was analyzed in terms of heat flow due to electron-phonon coupling, which was found stronger than estimated for heat relaxation by regular quasiparticles.

cond-mat.supr-con↗