41 research outputs found
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Serial Biasing Technique for Rapid Single Flux Quantum Circuits
Superconductor electronics based on the Single Flux Quantum (SFQ) technology are considered a strong contender for the ‘beyond CMOS’ future of digital circuits because of the high speed and low power dissipation associated with them. In fact, digital operations beyond tens of GHz have been routinely demonstrated in the SFQ technology. These circuits have widespread applications such as high-speed analog-to-digital conversion, digital signal processing, high speed computing and in emerging topics such as control circuitry for superconducting quantum computing.
Rapid Single Flux Quantum (RSFQ) circuits have emerged as a promising candidate within the SFQ technology, with information encoded in picosecond wide, milli-volt voltage pulses. As is the case with any integrated circuit technology, scalability of RSFQ circuits is essential to realizing their applications. These circuits, based on the Josephson junction, require a DC bias current for the correct operation. The DC bias current requirement increases with circuit complexity, and this has multiple implications on circuit operation. Large currents produce magnetic fields that can interfere with logic operation. Furthermore, the heat load delivered to the superconducting chip also increases with current which could result in the circuit becoming ‘normal’ and not superconducting. These problems make reduction of the bias current necessary.
Serial Biasing (SB) is a bias current reduction technique, that has been proposed in the past. In this technique, a digital circuit is partitioned into multiple identical islands and bias current is provided to each island in a serial manner. While this scheme is promising, there are multiple challenges such as design of the driver-receiver pair circuit resulting in robust and wide operating bias margins, current management on the floating islands, etc.
This thesis investigates SB in a systematic manner, focusing on the design and measurement of the fundamental components of this technique with an emphasis on reliability and scalability. It presents works on circuit techniques achieving high speed serially biased RSFQ circuits with robust operating margins and the experimental evidence to support the ideas. It develops a framework for serial biasing that could be used by electronic design tools to automate design and synthesis of complex RSFQ circuits. It also investigates Passive Transmission Lines (PTLs) for use as passive interconnects between library cells in a complex design, reducing the DC bias current required by the active circuitry
Spin Detection, Amplification, and Microwave Squeezing with Kinetic Inductance Parametric Amplifiers
Superconducting parametric amplifiers operating at microwave frequencies have become an essential component in circuit quantum electrodynamics experiments. They are used to amplify signals at the single-photon level, while adding only the minimum amount of noise required by quantum mechanics. To achieve gain, energy is transferred from a pump to the signal through a non-linear interaction. A common strategy to enhance this process is to place the non-linearity inside a high quality factor resonator, but so far, quantum limited amplifiers of this type have only been demonstrated from designs that utilize Josephson junctions. Here we demonstrate the Kinetic Inductance Parametric Amplifier (KIPA), a three-wave mixing resonant parametric amplifier that exploits the kinetic inductance intrinsic to thin films of disordered superconductors. We then utilize the KIPA for measurements of 209Bi spin ensembles in Si. First, we show that a KIPA can serve simultaneously as a high quality factor resonator for pulsed electron spin resonance measurements and as a low-noise parametric amplifier. Using this dual-functionality, we enhance the signal to noise ratio of our measurements by more than a factor of seven and ultimately achieve a measurement sensitivity of 2.4 x 10^3 spins. Then we show that pushed to the high-gain limit, KIPAs can serve as a `click'-detector for microwave wave packets by utilizing a hysteretic transition to a self-oscillating state. We calibrate the detector's sensitivity to be 3.7 zJ and then apply it to measurements of electron spin resonance. Finally, we demonstrate the suitability of the KIPA for generating squeezed vacuum states. Using a cryogenic noise source, we first confirm the KIPAs in our experiment to be quantum limited amplifiers. Then, using two KIPAs arranged in series, we make direct measurements of vacuum noise squeezing, where we generate itinerant squeezed states with minimum uncertainty more than 7 dB below the standard quantum limit.
High quality factor resonators have also recently been used to achieve strong coupling between the spins of single electrons in gate-defined quantum dots and microwave photons. We present our efforts to achieve the equivalent goal for the 31P flip-flop qubit. In doing so, we confirm previous predictions that the superconducting material MoRe would produce magnetic field-resilient resonators and demonstrate that it has kinetic inductance equivalent to the popular material NbTiN
Low Power Memory/Memristor Devices and Systems
This reprint focusses on achieving low-power computation using memristive devices. The topic was designed as a convenient reference point: it contains a mix of techniques starting from the fundamental manufacturing of memristive devices all the way to applications such as physically unclonable functions, and also covers perspectives on, e.g., in-memory computing, which is inextricably linked with emerging memory devices such as memristors. Finally, the reprint contains a few articles representing how other communities (from typical CMOS design to photonics) are fighting on their own fronts in the quest towards low-power computation, as a comparison with the memristor literature. We hope that readers will enjoy discovering the articles within
Extremely Large Area (88 mm X 88 mm) Superconducting Integrated Circuit (ELASIC)
Superconducting integrated circuit (SIC) is a promising "beyond-CMOS" device
technology enables speed-of-light, nearly lossless communications to advance
cryogenic (4 K or lower) computing. However, the lack of large-area
superconducting IC has hindered the development of scalable practical systems.
Herein, we describe a novel approach to interconnect 16 high-resolution deep UV
(DUV EX4, 248 nm lithography) full reticle circuits to fabricate an extremely
large (88mm X 88 mm) area superconducting integrated circuit (ELASIC). The
fabrication process starts by interconnecting four high-resolution DUV EX4 (22
mm X 22 mm) full reticles using a single large-field (44 mm X 44 mm) I-line
(365 nm lithography) reticle, followed by I-line reticle stitching at the
boundaries of 44 mm X 44 mm fields to fabricate the complete ELASIC field (88
mm X 88 mm). The ELASIC demonstrated a 2X-12X reduction in circuit features and
maintained high-stitched line superconducting critical currents. We examined
quantum flux parametron (QFP) circuits to demonstrate the viability of common
active components used for data buffering and transmission. Considering that no
stitching requirement for high-resolution EX4 DUV reticles is employed, the
present fabrication process has the potential to advance the scaling of
superconducting quantum devices
Revealing Josephson vortex dynamics in proximity junctions below critical current
Made of a thin non-superconducting metal (N) sandwiched by two
superconductors (S), SNS Josephson junctions enable novel quantum
functionalities by mixing up the intrinsic electronic properties of N with the
superconducting correlations induced from S by proximity. Electronic properties
of these devices are governed by Andreev quasiparticles [1] which are absent in
conventional SIS junctions whose insulating barrier (I) between the two S
electrodes owns no electronic states. Here we focus on the Josephson vortex
(JV) motion inside Nb-Cu-Nb proximity junctions subject to electric currents
and magnetic fields. The results of local (Magnetic Force Microscopy) and
global (transport) experiments provided simultaneously are compared with our
numerical model, revealing the existence of several distinct dynamic regimes of
the JV motion. One of them, identified as a fast hysteretic entry/escape below
the critical value of Josephson current, is analyzed and suggested for
low-dissipative logic and memory elements.Comment: 11 pages, 3 figures, 1 table, 43 reference
Understanding Quantum Technologies 2022
Understanding Quantum Technologies 2022 is a creative-commons ebook that
provides a unique 360 degrees overview of quantum technologies from science and
technology to geopolitical and societal issues. It covers quantum physics
history, quantum physics 101, gate-based quantum computing, quantum computing
engineering (including quantum error corrections and quantum computing
energetics), quantum computing hardware (all qubit types, including quantum
annealing and quantum simulation paradigms, history, science, research,
implementation and vendors), quantum enabling technologies (cryogenics, control
electronics, photonics, components fabs, raw materials), quantum computing
algorithms, software development tools and use cases, unconventional computing
(potential alternatives to quantum and classical computing), quantum
telecommunications and cryptography, quantum sensing, quantum technologies
around the world, quantum technologies societal impact and even quantum fake
sciences. The main audience are computer science engineers, developers and IT
specialists as well as quantum scientists and students who want to acquire a
global view of how quantum technologies work, and particularly quantum
computing. This version is an extensive update to the 2021 edition published in
October 2021.Comment: 1132 pages, 920 figures, Letter forma
DC flux parametron : a new approach to Josephson junction logic
ix, 200 p. : ill. ; 24 cm
Gigahertz Sub-Landauer Momentum Computing
We introduce a fast and highly-efficient physically-realizable bit swap.
Employing readily available and scalable Josephson junction microtechnology,
the design implements the recently introduced paradigm of momentum computing.
Its nanosecond speeds and sub-Landauer thermodynamic efficiency arise from
dynamically storing memory in momentum degrees of freedom. As such, during the
swap, the microstate distribution is never near equilibrium and the
memory-state dynamics fall far outside of stochastic thermodynamics that
assumes detailed-balanced Markovian dynamics. The device implements a bit-swap
operation -- a fundamental operation necessary to build reversible universal
computing. Extensive, physically-calibrated simulations demonstrate that device
performance is robust and that momentum computing can support
thermodynamically-efficient, high-speed, large-scale general-purpose computing
that circumvents Landauer's bound.Comment: 18 pages, 11 figures, 5 appendices;
http://csc.ucdavis.edu/~cmg/compmech/pubs/gslmc.ht
A Cost and Power Feasibility Analysis of Quantum Annealing for NextG Cellular Wireless Networks
In order to meet mobile cellular users' ever-increasing data demands, today's 4 G and 5 G wireless networks are designed mainly with the goal of maximizing spectral efficiency. While they have made progress in this regard, controlling the carbon footprint and operational costs of such networks remains a long-standing problem among network designers. This paper takes a long view on this problem, envisioning a NextG scenario where the network leverages quantum annealing for cellular baseband processing. We gather and synthesize insights on power consumption, computational throughput and latency, spectral efficiency, operational cost, and feasibility timelines surrounding quantum annealing technology. Armed with these data, we project the quantitative performance targets future quantum annealing hardware must meet in order to provide a computational and power advantage over CMOS hardware, while matching its whole-network spectral efficiency. Our quantitative analysis predicts that with 82.32 μ s problem latency and 2.68 M qubits, quantum annealing will achieve a spectral efficiency equal to CMOS while reducing power consumption by 41 kW (45% lower) in a Large MIMO base station with 400 MHz bandwidth and 64 antennas, and a 160 kW power reduction (55% lower) using 8.04 M qubits in a CRAN setting with three Large MIMO base stations
DC flux parametron : a new approach to Josephson junction logic
ix, 200 p. : ill. ; 24 cm