Broadband SNAIL parametric amplifier with microstrip impedance transformer

Josephson parametric amplifiers have emerged as a promising platform for quantum information processing and squeezed quantum states generation. Travelling wave and impedance-matched parametric amplifiers provide broad bandwidth for high-fidelity single-shot readout of multiple qubit superconducting circuits. Here, we present a quantum-limited 3-wave-mixing parametric amplifier based on superconducting nonlinear asymmetric inductive elements (SNAILs), whose useful bandwidth is enhanced with an on-chip two-section impedance-matching circuit based on microstrip transmission lines. The amplifier dynamic range is increased using an array of sixty-seven SNAILs with 268 Josephson junctions, forming a nonlinear quarter-wave resonator. Operating in a current-pumped mode, we experimentally demonstrate an average gain of $17 dB$ across $300 MHz$ bandwidth, along with an average saturation power of $- 100 dBm$, which can go as high as $- 97 dBm$ with quantum-limited noise performance. Moreover, the amplifier can be fabricated using a simple technology with just a one e-beam lithography step. Its central frequency is tuned over a several hundred megahertz, which in turn broadens the effective operational bandwidth to around $1.5 GHz$.Comment: 7 pages, 3 figure

Robust cryogenic matched low-pass coaxial filters for quantum computing applications

Electromagnetic noise is one of the key external factors decreasing superconducting qubits coherence. Matched coaxial filters can prevent microwave and IR photons negative influence on superconducting quantum circuits. Here, we report on design and fabrication route of matched low-pass coaxial filters for noise-sensitive measurements at milliKelvin temperatures. A robust transmission coefficient with designed linear absorption (-1dB/GHz) and ultralow reflection losses less than -20 dB up to 20 GHz is achieved. We present a mathematical model for evaluating and predicting filters transmission parameters depending on their dimensions. It is experimentally approved on two filters prototypes different lengths with compound of Cu powder and Stycast commercial resin demonstrating excellent matching. The presented design and assembly route are universal for various compounds and provide high repeatability of geometrical and microwave characteristics. Finally, we demonstrate three filters with almost equal reflection and transmission characteristics in the range from 0 to 20 GHz, which is quite useful to control multiple channel superconducting quantum circuits.Comment: 5 pages, 4 figure

High-Q trenched aluminum coplanar resonators with an ultrasonic edge microcutting for superconducting quantum devices

Dielectric losses are one of the key factors limiting the coherence of superconducting qubits. The impact of materials and fabrication steps on dielectric losses can be evaluated using coplanar waveguide (CPW) microwave resonators. Here, we report on superconducting CPW microwave resonators with internal quality factors systematically exceeding 5x106 at high powers and 2x106 (with the best value of 4.4x106) at low power. Such performance is demonstrated for 100-nm-thick aluminum resonators with 7-10.5 um center trace on high-resistivity silicon substrates commonly used in quantum Josephson junction circuits. We investigate internal quality factors of the resonators with both dry and wet aluminum etching, as well as deep and isotropic reactive ion etching of silicon substrate. Josephson junction compatible CPW resonators fabrication process with both airbridges and silicon substrate etching is proposed. Finally, we demonstrate the effect of airbridges positions and extra process steps on the overall dielectric losses. The best quality fa ctors are obtained for the wet etched aluminum resonators and isotropically removed substrate with the proposed ultrasonic metal edge microcutting.Comment: 6 pages, 2 figure

Sputtered NbN Films for Ultrahigh Performance Superconducting Nanowire Single-Photon Detectors

Nowadays ultrahigh performance superconducting nanowire single-photon detectors are the key elements in a variety of devices from biological research to quantum communications and computing. Accurate tuning of superconducting material properties is a powerful resource for fabricating single-photon detectors with a desired properties. Here, we report on the major theoretical relations between ultrathin niobium nitride (NbN) films properties and superconducting nanowire single-photon detectors characteristics, as well as ultrathin NbN films properties dependence on reactive magnetron sputtering recipes. Based on this study we formulate the exact requirements to ultrathin NbN films for ultrahigh performance superconducting nanowire single-photon detectors. Then, we experimentally study ultrathin NbN films properties (morphology, crystalline structure, critical temperature, sheet resistance) on silicon, sapphire, silicon dioxide and silicon nitride substrates sputtered with various recipes. We demonstrate ultrathin NbN films (obtained with more than 100 films deposition) with a wide range of critical temperature from 2.5 to 12.1 K and sheet resistance from 285 to 2000 ~$\Omega$/sq, as well as investigate a sheet resistance evolution over for more than 40\% within two years. Finally, we found out that one should use ultrathin NbN films with specific critical temperature near 9 K and sheet resistance of 400 ~$\Omega$/sq for ultrahigh performance SNSPD.Comment: The following article has been submitted to APL Materials. After it is published, it will be found at https://pubs.aip.org/aip/apm. Copyright 2023 Author(s). This article is distributed under a Creative Commons Attribution (CC BY) Licens

The Role of PETE in Developing and Sustaining Physical Literacy Informed Practitioners

This paper discusses teacher preparation in relation to encouraging and empowering future teachers to appreciate the potential and value of adopting physical literacy as the goal of PE. The paper addresses the issue of the role of schools and teacher training programs in developing the next generation of PE teachers entering PE Teacher Education (PETE) with respect to thoughts, feelings, perceptions, and beliefs that underpin the concept of physical literacy, and providing high quality learning experiences that are crucial to continuing physical activity throughout the life course for all children, not just those that have a natural aptitude in this area. Many advocates for radical change in physical education have repeatedly argued that physical education curricula around the world are too focused on a traditional, one size fits all, sport technique based, multi-activity form. Others have argued that the traditional curricula have a primary focus on physical competence in running, jumping, and balls skills rather than providing experience in a wide range of physical activities including, inter alia, those with a focus on aesthetic awareness and those related to outdoor adventure

AC 2007-754: A STEP IN THE RIGHT DIRECTION: STUDENT TRANSITION TO ENGINEERING PROGRAM A STEP in the Right Direction: Student Transition to Engineering Program

Abstract In 1995, Virginia Tech's Center for the Enhancement of Engineering Diversity (CEED) established and implemented a summer bridge program for pre-enrolled freshman students entering the College of Engineering in the subsequent fall. From 1995 to 2004, the program was targeted to under-represented engineering students under the name ASPIRE (The Academic Summer Program Introducing Resources for Engineers). In 2004, the CEED office received a $2 million dollar STEP (STEM Talent Expansion Program) grant from the National Science Foundation. The goal of the project is to increase the number of students earning degrees in engineering and computer science. One component of the grant activities was the expansion of ASPIRE, marketing it to a larger number of first-year students admitted to the College of Engineering (COE). The expanded bridge program still operates under the auspices of the CEED and has been named STEP Bridge -Student Transition to Engineering Program. Here, we provide a brief overview/history of ASPIRE and then discuss the transition to, and implementation of the STEP Bridge program. We will compare the logistics of managing both programs, costs, demographics of the populations served, fall semester academic performance of the participants as compared to appropriate non-participating cohorts, and student satisfaction with bridge programs. We will also project the program impact and discuss anticipated growing pains as we continue to expand to our target participation of 100 students. We will present what we have learned from the past two years of implementation, as STEP Bridge moves into its third year

Cross coupling of a solid-state qubit to an input signal due to multiplexed dispersive readout

The integration, scale up and multiplexing arrays of superconducting qubits in quantum circuits are one of the main challenges of superconducting quantum technology. Here, we experimentally investigate the solid-state qubit multiplexing readout scheme, containing coplanar quarter-wavelength resonators coupled with planar Xmon-type qubit, connected to a common coplanar transmission line. We find that the qubit energy spectrum modifies in the presence of an additional exciting signal at the neighbour resonators fundamental frequency. We attribute the origin of this effect to electromagnetic field propagating through the common ground plane, which changes the qubits characteristics. Our finding may be useful for the development of scalable superconducting quantum integrated circuits with arrays of multiplexed/coupled qubits for applications in superconducting quantum processing and computing