- Quantum Computation – ASC-2014 Plenary series – 4 of 13 – Tuesday 2014/8/12
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.
- Superconductive Energy-Efficient Computing – ASC-2014 Plenary-series – 6 of 13 – Wednesday 2014/8/13
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, 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.
- Superconducting Detectors for Astrophysics and Cosmology – ASC-2014 Plenary series – 9 of 13 – Thursday 2014/8/14
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.
- ASC-2014 Plenary series – 2 of 13 – Monday 2014/8/11
Perspective on Energy and the Power Sector by Ronald L. Schoff of the Electric Power Research Institute (EPRI) – at the 2014 Applied Superconductivity Conference in Charlotte, North Carolina.
- High-current HTS cables for magnet applications – ASC-2014 Plenary series – 8 of 13 – Thursday 2014/8/14
It has been more than 25 yeas 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?
- High Magnetic Field Science and its Application in the US – ASC-2014 Plenary series – 7 of 13 – Friday 2014/8/15
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.
- Cryogenics for Applied Superconductivity – ASC-2014 Plenary series – 11 of 13 – Friday 2014/8/15
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, low and easy maintenance to optimize system availability and minimize acquisition and operation cost.Depending on superconductor, operation temperature ranges from 1.8K up to 77K 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 – ASC-2014 Plenary series – 12 of 13 – Friday 2014/8/15
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.
- ASC-2014 Plenary series – 1 of 13 – Monday 2014/8/11
Welcome by Lee Mazzocchi of Duke Energy to the 2014 Applied Superconductivity Conference in Charlotte, North Carolina. — Video Sponsored by the IEEE Council on Superconductivity.
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