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Communications of the ACM 2017年第10期60卷 48-49页

作者： Mueller, Stephanie Baudisch, Patrick MIT's Electrical Engineering and Computer Science Department United States MIT CSAIL United States Hasso Plattner Institute Potsdam University Germany Human Computer Interaction Lab United States

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Rate-distance tradeoff and resource costs for all-optical quantum repeaters

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Physical Review A 2017年第1期95卷 012304-012304页

作者： Mihir Pant Hari Krovi Dirk Englund Saikat Guha Department of Electrical Engineering and Computer Science MIT Cambridge Massachusetts 02139 USA Quantum Information Processing Group Raytheon BBN Technologies 10 Moulton Street Cambridge Massachusetts 02138 USA

We present a resource-performance tradeoff of an all-optical quantum repeater that uses photon sources, linear optics, photon detectors, and classical feedforward at each repeater node, but no quantum memories. We show that the quantum-secure key rate has the form R(η)=Dηs bits per mode, where η is the end-to-end channel's transmissivity, and the constants D and s are functions of various device inefficiencies and the resource constraint, such as the number of available photon sources at each repeater node. Even with lossy devices, we show that it is possible to attain s<1, and in turn outperform the maximum key rate attainable without quantum repeaters, Rdirect(η)=−log2(1−η)≈(1/ln2)η bits per mode for η≪1, beyond a certain total range L, where η∼e−αL in optical fiber. We also propose a suite of modifications to a recently proposed all-optical repeater protocol that ours builds upon, which lower the number of photon sources required to create photonic clusters at the repeaters so as to outperform Rdirect(η), from ∼1011 to ∼106 photon sources per repeater node. We show that the optimum separation between repeater nodes is independent of the total range L and is around 1.5 km for assumptions we make on various device losses.

关键词： Photonics Quantum communication Quantum information with atoms & light

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Demonstration of hybrid foreground removal on CHIME data

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Physical Review D 2025年第10期111卷 103531-103531页

作者： Haochen Wang Kiyoshi Masui Kevin Bandura Arnab Chakraborty Matt Dobbs Simon Foreman Liam Gray Mark Halpern Albin Joseph Joshua MacEachern Juan Mena-Parra Kyle Miller Laura Newburgh Sourabh Paul Alex Reda Pranav Sanghavi Seth Siegel Dallas Wulf Department of Physics Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA MIT Kavli Institute for Astrophysics and Space Research Massachusetts Institute of Technology 77 Massachusetts Avenue Cambridge Massachusetts 02139 USA Lane Department of Computer Science and Electrical Engineering 1220 Evansdale Drive PO Box 6109 Morgantown West Virginia 26506 USA Center for Gravitational Waves and Cosmology West Virginia University Chestnut Ridge Research Building Morgantown West Virginia 26505 USA Department of Physics McGill University 3600 rue University Montréal Quebec H3A 2T8 Canada Trottier Space Institute McGill University 3550 rue University Montréal Quebec H3A 2A7 Canada Department of Physics Arizona State University Tempe Arizona USA Department of Physics and Astronomy University of British Columbia 6224 Agricultural Road Vancouver British Columbia V6T 1Z1 Canada Dunlap Institute for Astronomy & Astrophysics University of Toronto 50 Saint George Street Toronto Ontario M5S 3H4 Canada David A. Dunlap Department of Astronomy & Astrophysics University of Toronto 50 Saint George Street Toronto Ontario M5S 3H4 Canada Department of Physics Yale University New Haven Connecticut 06520 USA Jodrell Bank Centre for Astrophysics School of Physics and Astronomy The University of Manchester Manchester M13 9PL United Kingdom Perimeter Institute for Theoretical Physics 31 Caroline Street North Waterloo Ontario N25 2YL Canada

The main challenge of 21-cm cosmology experiments is astrophysical foregrounds that are difficult to separate from the signal due to telescope systematics. An earlier study has shown that foreground residuals induced by antenna gain errors can be estimated and subtracted using the hybrid foreground residual subtraction (HyFoReS) technique, which relies on cross-correlating linearly filtered data. In this paper, we apply a similar technique to the CHIME stacking analysis to subtract beam-induced foreground contamination. Using a linear high-pass delay filter for foreground suppression, the CHIME collaboration reported a 11.1σ detection in the 21-cm signal stacked on eBOSS quasar locations, despite foreground residual contamination mainly due to the instrument chromatic transfer function. Following the HyFoReS formalism, we cross-correlate the foreground-dominated data at low delay with the contaminated signal at high delay to estimate residual foregrounds and subtract them from the signal. We find that HyFoReS can improve the signal-to-noise ratio of the stacked 21-cm signal by 10%–20% after the delay foreground filter, although some of the improvement can also be achieved with an alternative flagging technique. We have shown that it is possible to use HyFoReS to reduce beam-induced foreground contamination, benefiting the analysis of the HI auto power spectrum with CHIME and enabling the recovery of large-scale modes.

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Waveguide quantum electrodynamics with giant superconducting artificial atoms

arXiv

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arXiv 2019年

作者： Kannan, Bharath Ruckriegel, Max Campbell, Daniel Kockum, Anton Frisk Braumüller, Jochen Kim, David Kjaergaard, Morten Krantz, Philip Melville, Alexander Niedzielski, Bethany M. Vepsäläinen, Antti Winik, Roni Yoder, Jonilyn Nori, Franco Orlando, Terry P. Gustavsson, Simon Oliver, William D. Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology CambridgeMA02139 United States Wallenberg Centre for Quantum Technology Department of Microtechnology and Nanoscience Chalmers University of Technology Gothenburg412 96 Sweden MIT Lincoln Laboratory 244 Wood Street LexingtonMA02420 United States Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Wako-shi Saitama351-0198 Japan Department of Physics University of Michigan Ann ArborMI48109-1040 United States Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States

Models of light-matter interactions typically invoke the dipole approximation [1], within which atoms are treated as point-like objects when compared to the wavelength of the electromagnetic modes that they interact with. However, when the ratio between the size of the atom and the mode wavelength is increased, the dipole approximation no longer holds and the atom is referred to as a "giant atom" [2]. Thus far, experimental studies with solid-state devices in the giant-atom regime have been limited to superconducting qubits that couple to short-wavelength surface acoustic waves [3–9], only probing the properties of the atom at a single frequency. Here we employ an alternative architecture that realizes a giant atom by coupling small atoms to a waveguide at multiple, but well separated, discrete locations. Our realization of giant atoms enables tunable atom-waveguide couplings with large on-off ratios [2] and a coupling spectrum that can be engineered by device design. We also demonstrate decoherence-free interactions between multiple giant atoms that are mediated by the quasi-continuous spectrum of modes in the waveguide–an effect that is not possible to achieve with small atoms [10]. These features allow qubits in this architecture to switch between protected and emissive configurations in situ while retaining qubit-qubit interactions, opening new possibilities for high-fidelity quantum simulations and non-classical itinerant photon generation [11, 12]. Copyright © 2019, The Authors. All rights reserved.

关键词： Atoms

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Detailed Characterization for TCAD Simulations of GaAs0.76P0.24/Si1-yGey/Si Single Junction Solar Cells

Detailed Characterization for TCAD Simulations of GaAs0.76P0...

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2017 IEEE 44th Photovoltaic Specialist Conference (PVSC)

作者： Sabina Abdul Hadi Timothy Milakovich Eugene A. Fitzgerald Ammar Nayfeh Department of Electrical Engineering and Computer Science (EECS) Masdar Institute Masdar City Abu Dhabi United Arab Emirates Department of Materials Science and Engineering MIT Cambridge MA USA

In this work a TCAD simulation model for GaAs 0.76 P 0.24 single junction solar cells grown on Si substrate via SiGe buffer layers is presented, along with experimental characterization of the cells. Simulations and experimental results are used to identify recombination factors present in the cells. GaAsP lifetime is estimated to be between 1-10 ns, depending on the window layer lifetime and interface recombination. Results show very good fit for current-voltage characteristics, while spectral response of simulated cells shows that more specific recombination definitions and accurate optical data are required to further improve the accuracy of simulation estimated recombination factors.

关键词： Radiative recombination Photovoltaic cells Charge carrier lifetime Optical buffering Optical device fabrication Optical reflection Temperature measurement

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Correction: Large-scale sensor systems based on graphene electrolyte-gated field-effect transistors

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The Analyst 2018年第2期143卷 580页

作者： Charles Mackin Tomás Palacios Department of Electrical Engineering & Computer Science Massachusetts Institute of Technology Cambridge MA 02139 USA. tpalacios@mit.edu.

Correction for 'Large-scale sensor systems based on graphene electrolyte-gated field-effect transistors' by Charles Mackin, et al., Analyst, 2016, 141, 2704-2711.

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Dense matter with eXTP

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science China(Physics,Mechanics & Astronomy) 2019年第2期62卷 28-44页

作者： Anna L.Watts WenFei Yu Juri Poutanen Shu Zhang Sudip Bhattacharyya Slavko Bogdanov Long Ji Alessandro Patruno Thomas E.Riley Pavel Bakala Altan Baykal Federico Bernardini Ignazio Bombaci Edward Brown Yuri Cavecchi Deepto Chakrabarty Jér?me Chenevez Nathalie Degenaar Melania Del Santo Tiziana Di Salvo Victor Doroshenko Maurizio Falanga Robert D.Ferdman Marco Feroci Angelo F.Gambino MingYu Ge Svenja K.Greif Sebastien Guillot Can Gungor Dieter H.Hartmann Kai Hebeler Alexander Heger Jeroen Homan Rosario Iaria Jean in 't Zand Oleg Kargaltsev Aleksi KurkelaTheoretical Physics Department CERN XiaoYu Lai Ang Li XiangDong Li ZhaoSheng Li Manuel Linares FangJun Lu Simin Mahmoodifar Mariano Méndez M.Coleman Miller Sharon Morsink Joonas N?ttil? Andrea Possenti Chanda Prescod-Weinstein JinLu Qu Alessandro Riggio Tuomo Salmi Andrea Sanna Andrea Santangelo Hendrik Schatz Achim Schwenk LiMing Song Eva?rámková Benjamin Stappers Holger Stiele Tod Strohmayer Ingo Tews Laura Tolos Gabriel T?r?k David Tsang Martin Urbanec Andrea Vacchi RenXin Xu YuPeng Xu Silvia Zane GuoBao Zhang ShuangNan Zhang WenDa Zhang ShiJie Zheng Xia Zhou Anton Pannekoek Institute for Astronomy University of Amsterdam Shanghai Astronomical Observatory Tuorla Observatory Department of Physics and Astronomy University of Turku Nordita KTH Royal Institute of Technology and Stockholm University Institute of High Energy Physics Chinese Academy Sciences Tata Institute of Fundamental Research Columbia Astrophysics Laboratory Columbia University Institut für Astronomie und Astrophysik Tübingen Universit?t Tübingen Leiden Observatory Leiden University Research Center for Computational Physics and Data Processing Silesian University in Opava Physics Department Middle East Technical University INAF Osservatorio Astronomico di Roma New York University Abu Dhabi Dipartimento di Fisica Enrico Fermi University of Pisa INFN Italian National Institute for Nuclear Physics Department of Physics and Astronomy Michigan State University Department of Astrophysical Sciences Princeton University Mathematical Sciences and STAG Research Centre University of Southampton MIT Kavli Institute for Astrophysics and Space Research DTU Space Technical University of Denmark INAF/IASF Palermo via Ugo La Malfa 153 Universita degli Studi di Palermo Dipartimento di Fisica e Chimica International Space Science Institute (ISSI) Faculty of Science University of East Anglia INAF Istituto di Astrofisica e Planetologie Spaziali Institut für Kernphysik Technische Universit?t Darmstadt ExtreMe Matter Institute EMMI GSI Helmholtzzentrum für Schwerionenforschung GmbH Instituto de Astrof'?sica Pontificia Universidad Católica de Chile Department of Physics & Astronomy Kinard Lab of Physics Clemson University School of Physics and Astronomy Monash University SRON Netherlands Institute for Space Research Department of Physics The George Washington University Faculty of Science and Technology University of Stavanger School of Physics and Mechanical & Electrical Engineering Hubei University of Education Department of Astronomy Xiamen University (Haiyun Campus) School of Astronomy and Space

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry(eXTP) mission for determining the nature of dense matter; neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of sciences, the eXTP mission is expected to be launched in the mid 2020 s.

关键词： neutron X-rays dense matter equation of state

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Effects of geometry and cochlear loads on tectorial membrane traveling waves

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AIP Conference Proceedings 2018年第1期1965卷

作者： Jonathan B. Sellon Roozbeh Ghaffari Dennis M. Freeman 1MIT Research Laboratory of Electronics Cambridge MA 02139 USA 2MIT Department of Electrical Engineering and Computer Science Cambridge MA 02139 USA

It has been suggested that the decay constants of tectorial membrane (TM) traveling waves contribute to differences in the tuning of Tectb −/– mutant mice, wild-type mice, and humans. However, the experiments underlying these results were obtained in vitro, in the absence of cochlear loads. In this work, we analyze effects of cochlear loads on TM traveling waves using a viscoelastic model. Results demonstrate that hair bundle stiffness has little effect on TM waves, the limbal attachment tends to increase the wavelength of TM waves, and viscous loss to subtectorial fluid tends to decrease the wave decay constant. To understand how the TM is able to support traveling waves despite these loads we examined how TM wave decay constants depend on thickness of the TM. We observe that increasing TM thickness tends to moderate all effects of cochlear loads and that as TM thickness increases, the wave decay constant approaches an asymptotic limit that is independent of cochlear loads. For material properties corresponding to both the apical and basal turns of the mouse TM, the asymptotic limit in decay constant is achieved at roughly the physiological thickness – suggesting an evolutionary pressure for the TM to be just thick enough to allow for wave propagation in the presence of subtectorial fluid.

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Supervised and unsupervised transfer learning for question answering

arXiv

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arXiv 2017年

作者： Chung, Yu-An Lee, Hung-Yi Glass, James MIT Computer Science and Artificial Intelligence Laboratory CambridgeMA United States Department of Electrical Engineering National Taiwan University Taipei Taiwan

Although transfer learning has been shown to be successful for tasks like object and speech recognition, its applicability to question answering (QA) has yet to be well-studied. In this paper, we conduct extensive experiments to investigate the transferability of knowledge learned from a source QA dataset to a target dataset using two QA models. The performance of both models on a TOEFL listening comprehension test (Tseng et al., 2016) and MCTest (Richardson et al., 2013) is significantly improved via a simple transfer learning technique from MovieQA (Tapaswi et al., 2016). In particular, one of the models achieves the state-of-the-art on all target datasets;for the TOEFL listening comprehension test, it outperforms the previous best model by 7%. Finally, we show that transfer learning is helpful even in unsupervised scenarios when correct answers for target QA dataset examples are not available. Copyright © 2017, The Authors. All rights reserved.

关键词： Machine learning

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Growth of InGaAs-channel transistor layers on large-scale Si wafers for HeteroIntegration with Si CMOS

Growth of InGaAs-channel transistor layers on large-scale Si...

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2017 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2017

作者： Nguyen, X.S. Yadav, S. Lee, K.H. Kohen, D. Kumar, A. Made, R.I. Gong, X. Lee, K.E. Tan, C.S. Yoon, S.F. Fitzgerald, E. Chua, S.J. Singapore-MIT Alliance for Research and Technology 1 CREATE Way Singapore138602 Singapore Department of Electrical and Computer Engineering National University of Singapore 21 Lower Kent Ridge Rd Singapore119077 Singapore School of Electrical and Electronic Engineering Nanyang Technological University 50 Nanyang Avenue Singapore639798 Singapore Department of Materials Science and Engineering Massachusetts Institute of Technology 77 Massachusetts Avenue CambridgeMA02139 United States

We report on the growth of In0.30Ga0.70As channel high-electron mobility transistor (HEMT) epi-layers on a 200 mm silicon wafer by metal organic chemical vapor deposition (MOCVD). The device epi-layers were grown on a silicon substrate by using a ∼ 3 μm thick buffer comprising a Ge layer, a GaAs layer and an InAlAs compositionally graded, strain relaxation layer. The achieved epitaxy has a threading dislocation density of (1 - 2) × 107 cm-2 and a root mean square surface roughness of 6-7 nm. The device active layers include a delta-doped InAlAs bottom barrier, a 15 nm thick InGaAs channel, a 15 nm InGaP top barrier layer and a heavily doped InGaAs contact layer. Long channel MOS-HEMT devices (LG ∼ 20 μm), were fabricated achieving a peak effective electron mobility of ∼ 3700 cm2/V·s.

关键词： High electron mobility transistors

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