The supernova SN 1987A has been observed with the JANZOS cosmic-ray facility at the Black Birch Range in New Zealand since October 1987. From May to July 1988, observations were carried out using the ...Cerenkov telescope at a zenith angle of 68 deg. By working at large zenith angles, the effective detection area and energy threshold are both increased. From 39 hr or greater of observation, an upper bound of 5.7 x 10 to the -14th/sq cm sec on the flux of gamma rays with energies of 75 TeV is obtained at the 95-percent confidence level. This flux limit corresponds to the gamma ray luminosity of 10 to the 37th ergs/sec. 20 refs.
Modeling and simulation is essential for predicting and verifying the behavior of fabricated quantum circuits, but existing simulation methods are either impractically costly or require an ...unrealistic simplification of error processes. We present a method of simulating noisy Clifford circuits that is both accurate and practical in experimentally relevant regimes. In particular, the cost is weakly exponential in the size and the degree of non-Cliffordness of the circuit. Our approach is based on the construction of exact representations of quantum channels as quasiprobability distributions over stabilizer operations, which are then sampled, simulated, and weighted to yield unbiased statistical estimates of circuit outputs and other observables. As a demonstration of these techniques we simulate a Steane 7,1,3-encoded logical operation with non-Clifford errors and compute its fault tolerance error threshold. We expect that the method presented here will enable studies of much larger and more realistic quantum circuits than was previously possible.
Developing devices that can reliably and accurately demonstrate the principles of superposition and entanglement is an on-going challenge for the quantum computing community. Modeling and simulation ...offer attractive means of testing early device designs and establishing expectations for operational performance. However, the complex integrated material systems required by quantum device designs are not captured by any single existing computational modeling method. We examine the development and analysis of a multi-staged computational workflow that can be used to design and characterize silicon donor qubit systems with modeling and simulation. Our approach integrates quantum computational chemistry calculations with electrostatic field solvers to perform detailed simulations of a phosphorus dopant in silicon. We show how atomistic details can be synthesized into an operational model for the logical gates that define quantum computation in this particular technology. The resulting computational workflow realizes a design tool for silicon donor qubits that can help verify and validate current and near-term experimental devices.
Development of ultra low background gas proportional counters has made the contribution from naturally occurring radioactive isotopes -- primarily \(\alpha\) and \(\beta\) activity in the uranium and ...thorium decay chains -- inconsequential to instrumental sensitivity levels when measurements are performed in above ground surface laboratories. Simple lead shielding is enough to mitigate against gamma rays as gas proportional counters are already relatively insensitive to naturally occurring gamma radiation. The dominant background in these surface laboratory measurements using ultra low background gas proportional counters is due to cosmic ray generated muons, neutrons, and protons. Studies of measurements with ultra low background gas proportional counters in surface and underground laboratories as well as radiation transport Monte Carlo simulations suggest a preferred conceptual design to achieve the highest possible sensitivity from an array of low background gas proportional counters when operated in a surface laboratory. The basis for a low background gas proportional counter array and the preferred shielding configuration is reported, especially in relation to measurements of radioactive gases having low energy decays such as \(^{37}\)Ar.
This is an updated version of supplementary information to accompany "Quantum supremacy using a programmable superconducting processor", an article published in the October 24, 2019 issue of Nature. ...The main article is freely available at https://www.nature.com/articles/s41586-019-1666-5. Summary of changes since arXiv:1910.11333v1 (submitted 23 Oct 2019): added URL for qFlex source code; added Erratum section; added Figure S41 comparing statistical and total uncertainty for log and linear XEB; new References 1,65; miscellaneous updates for clarity and style consistency; miscellaneous typographical and formatting corrections.
The emergence of streaming multicore processors with multi-SIMD architectures and ultra-low power operation combined with real-time compute and I/O reconfigurability opens unprecedented opportunities ...for executing sophisticated signal processing algorithms faster and within a much lower energy budget. Here, we present an unconventional FFT implementation scheme for the IBM Cell, named transverse vectorization. It is shown to outperform (both in terms of timing or GFLOP throughput) the fastest FFT results reported to date in the open literature.
The 3B/X13 solar flare beginning at 2356 UT on April 24, 1984 was identified as a solar neutron event by the gamma-ray spectrometer on the Solar Maximum Mission spacecraft and by the observation of ...protons resulting from neutron decay by the University of Chicago experiment on board the ISEE 3 spacecraft. Evidence for a possible ground-based response to the solar neutrons was not reported until recently. In this paper, the neutron monitor data for locations within 50 deg of the subsolar point during the solar flare event are presented and analyzed. The difficulties in identifying this possible ground-based response are discussed in detail. 16 refs.
We describe a new method for calculating geomagnetic cutoffs that incorporates obliquely incident primaries, and we use it to interpret a sea level neutron monitor latitude survey. Effects due to ...obliquely incident primaries are significant and may be responsible for anomalies observed in this and other latitude surveys. We define an 'apparent' cutoff that takes these obliquely incident particles into account. Use of our apparent cutoff in a Dorman function fit to the 1994-1995 Bartol Research Institute-University of Tasmania latitude survey data results in a significant improvement over use of the more conventional effective vertical cutoff. (Author)
High performance FFT on multicore processors Barhen, J; Kotas, C; Humble, T S ...
2010 Proceedings of the Fifth International Conference on Cognitive Radio Oriented Wireless Networks and Communications,
2010-June
Conference Proceeding
Odprti dostop
Importance of achieving high performance Fourier transforms for Cognitive Radio applications can not be over-emphasized. This includes signal detection in the presence of noise power uncertainty, ...multi-resolution spectrum sensing, minimization of subcarriers' side lobes in OFDM modulators, multi-stream processing, or spectrum loading, for example. With the emergence of advanced multicore processors, there is a remarkable opportunity to develop novel, massively parallel implementations of the FFT. This paper reviews recent advances in the area, and presents results for three classes of devices: the IBM Cell multi-SIMD processor, the Nvidia Tesla SIMT processor, and the EnLight digital optical core device.
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