Plenary Series at Applied Superconductivity Conference 2014 (ASC 2014)

• Welcome to Charlotte & Duke Energy Vision - Presented by Lee Mazzocchi
• Energy Efficiency Challenge - Presented by Ronald Schoff
• Superconducting Qubits Poised for Fault-tolerant Quantum Computation - Presented by John Martinis
• Niobium Manufacturing Technology for Superconducting Applications – from Mining to Finished Products - Presented by Tadeu Carneiro
• Superconductive Energy-Efficient Computing - Presented by Oleg Mukhanov
• Advances in MgB₂ Conductors - Presented by Rene Flukiger
• High-current HTS Cables for Magnet Applications - Presented by Luisa Chiesa
• Superconducting Detectors for Astrophysics and Cosmology - Presented by Jonas Zmuidzinas
• NRC Proposal for High-magnetic Field Research in the United States - Presented by Greg Boebinger
• Cryorefrigeration for Applied Superconductivity - Presented by Alain Ravex
• Laser Communication from Space Using Superconducting Detectors - Presented by Don Boroson
• Superconducting Maglev – Development and Progress Toward Revenue Service - Presented by Naoyuki Ueno

Welcome to Charlotte & Duke Energy Vision

Presenter: Lee Mazzocchi

Welcome by Lee Mazzocchi of Duke Energy to the 2014 Applied Superconductivity Conference in Charlotte, North Carolina.

Energy Efficiency Challenge

Presenter: Ronald Schoff

Perspective on Energy and the Power Sector by Ronald L. Schoff of the Electric Power Research Institute (EPRI) at the Applied Superconductivity Conference 2014 in Charlotte, North Carolina.

Superconducting Qubits Poised for Fault-tolerant Quantum Computation

Presenter: John Martinis

Superconducting quantum computing is now at an important crossroad, where “proof of concept” experiments involving small numbers of qubits can be transitioned to more challenging and systematic approaches that could actually lead to building a quantum computer.  Our optimism is based on two recent developments: a new hardware architecture for error detection based on “surface codes”, and recent improvements in the coherence of superconducting qubits.  I will explain how the surface code is a major advance for quantum computing, as it allows one to use qubits with realistic fidelities, and has a connection architecture that is compatible with integrated circuit technology.  We have also recently demonstrated a universal set of logic gates in a superconducting Xmon qubit that achieves single-qubit gate fidelity of 99.92% and a two-qubit gate fidelity up to 99.4%. This places Josephson quantum computing at the fault-tolerant threshold for surface code error correction. Our quantum processor is a first step towards the surface code, using five qubits arranged in a linear array with nearest-neighbor coupling. Using this device we have further demonstrated generation of the five-qubit Greenberger-Horne-Zeilinger (GHZ) state using the complete circuit and full set of gates, giving a state fidelity of 82% and a Bell state (2 qubit) fidelity of 99.5%.  These results demonstrate that Josephson quantum computing is a high-fidelity technology, with a clear path to scaling up to large-scale, fault-tolerant quantum circuits.

Niobium Manufacturing Technology for Superconducting Applications – from Mining to Finished Products

Presenter: Tadeu Carneiro

We present in vivo images of the human brain acquired with an ultralow field magnetic resonance imaging (ULFMRI) system operating at a field B₀ ≈ 130 microtesla. The system features prepolarization of the proton spins at a field B_p ≈ 0.1 T and detection of the nuclear magnetic resonance signals with a SQUID-based, superconducting, second-derivative gradiometer. We report measurements of the longitudinal relaxation time T1 of brain tissue, cerebrospinal fluid (CSF), blood and scalp fat at both B₀ and B_p. These measurements enable us to construct inversion recovery sequences that we combine with a Carr-Purcell-Meiboom-Gill (CPMG) echo train to obtain images in which any given tissue can be nulled out and another tissue highlighted. Such techniques greatly enhance the already high intrinsic T1-contrast obtainable at ULF. We illustrate the power of this technique with an image showing only the superior sagittal sinus, with other components eliminated. We further show that, as expected at ULF, the transverse relaxation time T2 approaches T1 in all four brain components. We present T2-weighted images that with our technique can be acquired in about 20% of the time required for T1-weighted images and comparable tissue contrast. With the use of multiple sensors, for example those in a SQUID-based system for magnetic source imaging, we believe these techniques would enable one to obtain high-contrast imaging of the components of the brain, including the visualization of brain tumors without the need of a contrast agent.

Superconductive Energy-Efficient Computing

Presenter: Oleg Mukhanov

Superconducting digital electronics is experiencing one of the largest transformations in the last two decades. This dramatic change is triggered by the recent shift from performance to energy efficiency as the primary metric dictating the course of computing progress across all technologies from CMOS to new nano-devices. This was caused by the run-away increase of power requirements of modern data centers and next generation of supercomputers. Until recently, superconducting digital circuits based on conventional Rapid Single Flux Quantum (RSFQ) logic were aimed to achieving higher and higher speed. Now, the low power and high energy-efficiency dominate the requirements for computing from high-end supercomputers to circuits controlling qubits and processing cryogenic detector outputs. As a result, a number of low-power post-RSFQ logic families have been introduced. The ultimately low power dissipation can even reach below the thermodynamic limit in physically and logically reversible circuits. Furthermore, the augmentation of traditional Josephson junctions with spintronic elements, inclusion of ferromagnetic layers, and hybridization with semiconductor elements significantly enhances functional capabilities of superconducting digital technologies.  These lead to solving long-standing, hard problems of cryogenic dense memories capable of working with SFQ digital circuits and high-bandwidth interfaces from cryogenic to room temperature electronics, which were the biggest impediments for the growth of superconducting digital electronics. Among these new devices are superconductor-ferromagnetic magnetic Josephson junctions combining superconductivity and ferromagnetism, two antagonistic order parameters, leading to the device characteristics unattainable in pure superconducting or magnetic structures. The properties of such magnetic junctions can be made compatible to traditional Josephson junctions and integrated into a single circuit. High complexity superconductive computing is impossible without a high-yield, high integration density fabrication process capable of producing complex microprocessor and memory chips. The recent resurgence of process techniques paves a way to integrating digital processing and memory circuits, leading to computing microarchitecture options unavailable earlier. Careful selection and adaptation of architectures for the implementation of superconductive computing circuits and systems can achieve better utilization of a potential offered by superconductivity and provide a significant advantage compare to other technologies. These innovations happened just within last few years dramatically increase a potential of superconductivity addressing many known critical problems which prevented the insertion of superconductivity into computing applications in the past.

Advances in MgB₂ Conductors

Presenter: Rene Flukiger

The compound MgB₂ (T_c = 39K) occupies an intermediate position between LTS and HTS superconductors. It is a two-band superconductor with a complex, non-BCS behavior of the anisotropic properties as a function of magnetic field and temperature. On the other hand, some properties can be described by a conventional phonon-mediated mechanism of superconductivity.  The application range of this material is restricted by its low irreversibility field, which does not exceed 25T, even in wires with carbon additives. However, for intermediate fields and T ≤ 25K this disadvantage with respect to HTS materials is compensated by production costs being more than one order of magnitude lower (< 3 $/kAm): for selected applications, MgB₂ appears thus increasingly as an alternative solution to HTS materials.  Various powder metallurgical approaches are known for the fabrication of multifilamentary MgB₂ wires up to lengths beyond 10 km. It has been found that the optimization of J_c in wires requires nanosize powders (this holds particularly for B as well as for carbon dopants). An additional requirement is a high mass density in the filaments, leading to enhanced grain connectivity. The presently applied processing techniques are reviewed.  The first industrial application of MgB₂ was the production of open-sky MRI magnets operating at 20 K. The great potential of this material for the transmission of electrical power has been recently demonstrated at CERN, where a 20 meter MgB₂ cable carrying 20 kA in He gas at 24 K was successfully tested in view of current leads for the High-Luminosity LHC project. In the Ignitor fusion project, the two outer poloidal field coils will be based on MgB₂ strands. Future projects will also include LH₂ cooled MgB₂ cables: a first MgB₂ cable carrying 3 kA at 20 K has already been successfully tested in Moscow. Recently, a new hybrid energy storage concept, has been proposed at KTI (D), which combines the use of liquid hydrogen as the bulk energy carrier with superconducting magnetic energy storage (SMES). With the expected increase of the share of renewable power in the energy mix, efficient long distance electricity transport infrastructure has become a strategic priority: MgB₂ cables as an alternative to standard HVDC (High Voltage Direct Current) power lines are under study. Finally, calculations have shown that MgB₂ would be the most cost-effective option in view of large rotating machines, e.g. wind turbine generators at ≥ 5 MW. Cost-efficiency is the driving force behind the future applications of MgB₂, which will be briefly presented. 

It has been more than 25 years since the discovery of High Temperature Superconductors and following their utilization in power cable applications and layer-wound magnets, they are now being considered for future high-current, high-field magnets typically used in high-energy physics and fusion machines. Discussions of the requirements and the desired targets needed for applications using high-current and high-field magnets will be presented together with a summary of the present status of the conductors currently being developed.  Various cable concepts to be used in large magnets and their advantages and disadvantages will be discussed addressing the following: What can we do with the conductors we have? What do we need and how can we achieve it? 

Superconducting Detectors for Astrophysics and Cosmology

Presented by: Jonas Zmuidzinas

Where did Earth’s water come from? Although we can’t yet fully answer this question, a comet whose water has the same D/H ratio as the Earth’s oceans has now been found. Water vapor from the dwarf planet Ceres has also been detected recently, boosting anticipation of the arrival of NASA’s ion-propelled Dawn spacecraft at Ceres in February 2015. And on March 17, 2014, the BICEP2 team made international headlines with their announcement of evidence for gravitational waves produced during a sudden inflationary expansion of the universe when it was only 10^-35 seconds old. These three spectacular scientific discoveries are just a few examples of the impact that superconducting detectors are now making on the fields of cosmology, astrophysics, and planetary science. I will review the historical development of several types of superconducting detectors, discuss their role in major astronomy projects and the discoveries mentioned above, highlight the wide variety of superconducting phenomena exploited in these devices, indicate the impact on other fields, and close with some thoughts about future developments in this area.

NRC Proposal for High-magnetic Field Research in the United States

Presented by: Greg Boebinger

The United States’ National High Magnetic Field Laboratory (MagLab) hosts an international user community that spans condensed matter physics, materials research, chemistry, biology and biomedicine. We have developed a variety of unique magnets in service to our user community, ranging from the highest fields (21T) available for vertebrate MRI to the non-destructive generation of pulsed magnetic fields exceeding two million times the Earth’s magnetic field.  This talk seeks to answer the question “Why would anyone want to do such things?”,  which is curiously the same question taken up by the recent NRC “MagSci” study.  Particular focus will be given to the role of high-temperature superconductors (HTS) and HTS technologies required for the development of next generation magnets proposed in the MagSci study.

Cryorefrigeration for Applied Superconductivity

Presented by: Alain Ravex

Cryogenic cooling system, including both cryogenic source and thermal coupling to application, is a critical component of any applied superconductivity device. End users require high reliability, high efficiency, and low and easy maintenance to optimize system availability and minimize acquisition and operation cost. Depending on superconductor, operation temperature ranges from 1.8 K up to 77 K and depending on application cooling power ranges from milliWatts up to tens of KWatts: different technologies will obviously be required! The experience learned from decades of NbTi based applications operation will be remained. For new HTS potential applications, state of the art of commercially available cooling technologies will be summarized and on going developments and potential new solutions will be discussed both for cryorefrigerators and their integration.

Laser Communication from Space Using Superconducting Detectors

Presented by: Don Boroson

In the fall of 2013, NASA's Lunar Laser Communication Demonstration successfully demonstrated high-rate laser communications between a lunar-orbiting satellite and terrestrial ground stations.  The MIT Lincoln Laboratory-designed and built system included a number of novel features both in the space segment and in the ground segment.  The 622 Mbps downlink was made possible with only relatively small receive telescopes by employing a novel receiver based on Superconducting Nanowire Single Photon Detector (SNSPD) arrays.  In this presentation, we will present an overview of the mission, the drivers on downlink performance, and the Lincoln Laboratory-built SNSPD system that enabled it, including its basic specifications and its supporting electronics.

Superconducting Maglev – Development and Progress Toward Revenue Service

Presented by: Naoyuki Ueno

The Superconducting Maglev (SCMAGLEV) is a next generation transportation system that levitates and accelerates by the magnetic force generated between the onboard superconducting magnets and the coils attached to the guideway, enabling stable ultra-high speed operation at a speed of 500 km/h (311 mph). This cutting-edge technology is currently developed by JR Central, a railway company in Japan operating the Tokaido Shinkansen and surrounding conventional lines. The SCMAGLEV uses linear synchronous motor (LSM) for propulsion and electro-dynamic suspension (EDS) for levitation and guidance. The key component of this system is the onboard superconducting magnet, which houses niobium-titanium alloy cooled by liquid helium at -269°C (-452°F). By adopting powerful and energy efficient superconducting magnet, SCMAGLEV can levitate with large air gap of 10 cm (4 in) and thus can safely operate at ultra-high speed in the earthquake prone Japan. Research on a linear motor propulsion magnetically levitated railway system began in 1962 in Japan. From 1997, running tests are conducted on the Yamanashi Maglev Test Line (18.4 km or 11.4 mile), and implemented various tests including multiple train operation tests, high-speed passing tests, one-day continuous running tests, etc. On December 2003, the world speed record of 581 km/h (361 mph) is achieved with manned vehicle. In July 2009, the Maglev Technological Practicality Evaluation Committee under the Japanese government has acknowledged that “the technologies of the Superconducting Maglev have been established comprehensively and systematically.”  JR Central is currently promoting a new high speed line called Chuo Shinkansen with using SCMAGLEV system. As a bypass route to the current Tokaido Shinkansen, the Chuo Shinkansen will connect Japan’s principal metropolitan areas of Tokyo, Nagoya, and Osaka. It is planned to start revenue operation between Tokyo and Nagoya in 2027 and further extension to Osaka in 2045, and the travel time between Tokyo to Osaka will be shortened to 67 minutes where current Tokaido Shinkansen takes 2 hour and 30 minutes. In 2011, MLIT designated JR Central as the operator and constructor of the Chuo Shinkansen and instructed to construct. JR Central is now promoting the assessment of environmental impact, and after completion of the assessment procedure, the actual construction will take place. Meanwhile, running tests on the Yamanashi Maglev Test Line were temporary suspended from September 2011 for full renewal and extension to a length of 42.8 km (26.6 miles). From August 2013, running test has resumed with new vehicle called Series L0 (L zero), which is the first generation SCMAGLEV rolling stock that is designed to meet the revenue service specifications. We will present the development of the SCMAGLEV and the recent progress on the Chuo Shinkansen development toward revenue service.