Benchmarking the noise sensitivity of different parametric two-qubit gates in a single superconducting quantum computing platform

The possibility to utilize different types of two-qubit gates on a single quantum computing platform adds flexibility in the decomposition of quantum algorithms. A larger hardware-native gate set may decrease the number of required gates, provided that all gates are realized with high fidelity. Here, we benchmark both controlled-Z (CZ) and exchange-type (iSWAP) gates using a parametrically driven tunable coupler that mediates the interaction between two superconducting qubits. Using randomized benchmarking protocols we estimate an error per gate of $0.9\pm0.03\%$ and $1.3\pm0.4\%$ fidelity for the CZ and the iSWAP gate, respectively. We argue that spurious $ZZ$-type couplings are the dominant error source for the iSWAP gate, and that phase stability of all microwave drives is of utmost importance. Such differences in the achievable fidelities for different two-qubit gates have to be taken into account when mapping quantum algorithms to real hardware.Comment: 24 pages, including supplementary informatio

Ultrahigh Vacuum Packaging and Surface Cleaning for Quantum Devices

We describe design, implementation and performance of an ultra-high vacuum (UHV) package for superconducting qubit chips or other surface sensitive quantum devices. The UHV loading procedure allows for annealing, ultra-violet light irradiation, ion milling and surface passivation of quantum devices before sealing them into a measurement package. The package retains vacuum during the transfer to cryogenic temperatures by active pumping with a titanium getter layer. We characterize the treatment capabilities of the system and present measurements of flux tunable qubits with an average T$_1=84~\mu$s and T$^{echo}_2=134~\mu$s after vacuum-loading these samples into a bottom loading dilution refrigerator in the UHV-package.Comment: 5 pages, 6 figure

Impact of interface traps on charge noise, mobility and percolation density in Ge/SiGe heterostructures

Hole spins in Ge/SiGe heterostructure quantum dots have emerged as promising qubits for quantum computation. The strong spin-orbit coupling (SOC), characteristic of heavy-hole states in Ge, enables fast and all-electrical qubit control. However, SOC also increases the susceptibility of spin qubits to charge noise. While qubit coherence can be significantly improved by operating at sweet spots with reduced hyperfine or charge noise sensitivity, the latter ultimately limits coherence, underlining the importance of understanding and reducing charge noise at its source. In this work, we study the voltage-induced hysteresis commonly observed in SiGe-based quantum devices and show that the dominant charge fluctuators are localized at the semiconductor-oxide interface. By applying increasingly negative gate voltages to Hall bar and quantum dot devices, we investigate how the hysteretic filling of interface traps impacts transport metrics and charge noise. We find that the gate-induced accumulation and trapping of charge at the SiGe-oxide interface leads to an increased electrostatic disorder, as probed by transport measurements, as well as the activation of low-frequency relaxation dynamics, resulting in slow drifts and increased charge noise levels. Our results highlight the importance of a conservative device tuning strategy and reveal the critical role of the semiconductor-oxide interface in SiGe heterostructures for spin qubit applications

ГЛАГОЛЫ ДВИЖЕНИЯ РУССКОГО ЯЗЫКА (сборник таблиц и упражнений слушателям подготовительного отделения для иностранных граждан)

Представлены русские глаголы, обозначающие способы передвижения в пространстве, формы и случаи употребления глаголов движения в языке для изучения иностранными студентами подготовительного отделения (сборник таблиц и упражнений)

Capacitive crosstalk in gate-based dispersive sensing of spin qubits

In gate-based dispersive sensing, the response of a resonator attached to a quantum dot gate is detected by a reflected radio-frequency signal. This enables fast readout of spin qubits and tune up of arrays of quantum dots, but comes at the expense of increased susceptibility to crosstalk, as the resonator can amplify spurious signals and induce fluctuations in the quantum dot potential. We attach tank circuits with superconducting NbN inductors and internal quality factors $Q_{\mathrm{i}}$>1000 to the interdot barrier gate of silicon double quantum dot devices. Measuring the interdot transition in transport, we quantify radio-frequency crosstalk that results in a ring-up of the resonator when neighbouring plunger gates are driven with frequency components matching the resonator frequency. This effect complicates qubit operation and scales with the loaded quality factor of the resonator, the mutual capacitance between device gate electrodes, and with the inverse of the parasitic capacitance to ground. Setting qubit frequencies below the resonator frequency is expected to substantially suppress this type of crosstalk.Comment: 7 pages, 4 figures, supplementary informatio

Электроимпульсный пробой и разрушение горных пород и твердых диэлектриков при воздействии разнополярных импульсов напряжения

Исследования электрической прочности внедрения канала разряда в горные породы при одновременном воздействии разнополярных импульсах высокого напряжения.In the dielectric displacement course in an electric field become two phenomena groups apparent. The first group is peculiar for dialectic only. The internal charged particles will always exist if the dielectric is placed in an electric field. Hence, the opposite electric charges will be shifted in relation to each other

FRC-QE: a robust and comparable 3D microscopy image quality metric for cleared organoids

Three-dimensional stem-cell-derived organoids are a powerful tool for studying cellular processes in tissue-like structures, enabling in vitro experiments in an organ-specific context. While organoid research has been closely linked to advances in fluorescence microscopy, capturing cellular structures within their global context in an organoid often remains challenging due to the organoid’s dense structure and opacity. The development of optical clearing methods has provided a solution for fixed organoids but optimizing clearing protocols for a given sample type and staining can be challenging. Importantly, quantitative measures for assessing image quality throughout cleared fluorescent samples are missing. Here, we propose Fourier ring correlation quality estimation (FRC-QE) as a new metric for automated 3D image quality estimation in cleared organoids. We show that FRC-QE robustly captures differences in clearing efficiency within an organoid, across replicates and clearing protocols, as well as for different microscopy modalities. FRC-QE is open-source, written in ImgLib2 and provided as an easy-to-use and macro-scriptable plugin for the popular Fiji software. We therefore envision FRC-QE to fill the gap of providing a reliable quality metric for testing, optimizing and comparing optical clearing methods