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DTSTART;TZID=UTC:20250501T160000
DTEND;TZID=UTC:20250501T170000
DTSTAMP:20260414T184255
CREATED:20250425T165631Z
LAST-MODIFIED:20250425T165631Z
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SUMMARY:Speaker: Kevin O'Brien (MIT) - Title: Broadband quantum-limited amplification and near-ultrastrong light-matter coupling with superconducting circuits
DESCRIPTION:Research Progress Meeting \nDate: May 1\, 2025 \nTime: 4:00- 5:00 pm \nLocation: Sessler Conference Room- 50A-5132 [In-Person and HYBRID]  \nSpeaker: Kevin O’Brien (MIT) \nTitle: Broadband quantum-limited amplification and near-ultrastrong light-matter coupling with superconducting circuits \nAbstract: Superconducting qubits are one of the leading quantum computing platforms in part due to the nonlinearity of the Josephson junction. High quantum efficiency broadband amplification is a key requirement for high fidelity qubit readout and thus implementing quantum error correction. We illustrate the modeling and design of high quantum efficiency broadband parametric amplifiers using our open source package JosephsonCircuits.jl [1]. These amplifiers are engineered to match the Floquet modes in the amplifier to the eigenmodes of the environment\, eliminating a previously ubiquitous noise mechanism in broadband amplifiers [2]. We present the fabrication of such amplifiers using a high-Q qubit fabrication process with state of the art junction critical current uniformity. We detail the characterization of these amplifiers including the highest reported quantum efficiency for a traveling wave parametric amplifier [3] and future directions of on-chip integration and isolation. Finally\, we show how qubits with quartic [4] rather than the familiar weakly anharmonic potential enable the first demonstration of near-ultrastrong nonlinear coupling [5] with applications in fast qubit readout [6] and gates. \n[1] K. Peng\, R. Poore\, P. Krantz\, D. E. Root\, and K. P. O’Brien “X-parameter based design and simulation of Josephson traveling-wave parametric amplifiers for quantum computing applications” IEEE QCE22 (2022)\n[2] K. Peng\, M. Naghiloo\, J. Wang\, G. D. Cunningham\, Y. Ye\, and K. P. O’Brien “Floquet-Mode Traveling-Wave Parametric Amplifiers” PRX Quantum 3\, 020306 (2022)\n[3] J. Wang*\, K. Peng*\, G. D. Cunningham\, A. Lombo\, A. Yen\, D. Zaidenberg\, W. D. Oliver\, K. P. O’Brien “High-Efficiency\, Low-Loss Floquet-Mode Traveling-Wave Parametric Amplifier” arxiv 2503.11812 (2025)\n[4] Y. Ye\, K. Peng\, M. Naghiloo\, G. Cunningham\, K. P. O’Brien “Engineering purely nonlinear coupling between superconducting qubits using a quarton” Physical Review Letters 127 (5)\, 050502 (2022)\n[5] Y. Ye\, J. B. Kline\, A. Yen\, G. Cunningham\, M. Tan\, A. Zang\, M. Gingras\, B. M. N.\, H. Stickler\, K. Serniak\, M. E. Schwartz\, K. P. O’Brien “Near-ultrastrong nonlinear light-matter coupling in superconducting circuits” arXiv:2404.19199 (2024)\n[6] Y. Ye\, J. B. Kline\, S. Chen\, A. Yen\, K. P. O’Brien “Ultrafast superconducting qubit readout with the quarton coupler” Science Advances 10 (41)\, eado9094 (2024) \nhttps://lbnl.zoom.us/j/98854322464?pwd=K2tKUm1VZjRlV1J5RHE3cXdHQzRxdz09 \nMeeting ID: 988 5432 2464\n\nPasscode: 142239
URL:https://rpm.physics.lbl.gov/event/speaker-kevin-obrien-mit-title-broadband-quantum-limited-amplification-and-near-ultrastrong-light-matter-coupling-with-superconducting-circuits/
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BEGIN:VEVENT
DTSTART;TZID=UTC:20250508T160000
DTEND;TZID=UTC:20250508T170000
DTSTAMP:20260414T184255
CREATED:20250503T151248Z
LAST-MODIFIED:20250503T151248Z
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SUMMARY:Speaker: Josh Dillon (UC Berkeley) - Title: Recent Progress in 21 cm Cosmology with the Hydrogen Epoch of Reionization Array
DESCRIPTION:Research Progress Meeting \nDate: May 8\, 2025 \nTime: 4:00- 5:00 pm \nLocation: Sessler Conference Room- 50A-5132 [In-Person and HYBRID]  \nSpeaker: Josh Dillon (UC Berkeley) \nTitle: Recent Progress in 21 cm Cosmology with the Hydrogen Epoch of Reionization Array \nAbstract: 21 cm cosmology promises a revolutionary new probe of the astrophysics and cosmology of the Cosmic Dawn and the epoch of reionization (EoR). I will discuss our progress with the Hydrogen Epoch of Reionization Array (HERA)\, an interferometer in South Africa with 350 14-m dishes\, purpose-built for 21 cm cosmology. With early HERA data and only a small fraction of its final size and bandwidth\, we have set world-leading limits on the 21 cm power spectrum. These results already have important astrophysical implications: they largely rule out “cold reionization” scenarios\, provide a lower bound on the X-ray heating of the intergalactic medium\, and constrain models of its origin. We are now preparing our first limits from HERA’s new broadband system (5 < z < 25)\, which should lay the groundwork for future results that realize the instrument’s full potential. In this talk\, I will present these limits\, their interpretation\, and their statistical validation. Finally\, I will look forward to the exciting science we can expect in the next few years from HERA\, as well as the lessons it holds for future arrays for 21 cm cosmology. \nhttps://lbnl.zoom.us/j/98854322464?pwd=K2tKUm1VZjRlV1J5RHE3cXdHQzRxdz09 \nMeeting ID: 988 5432 2464\n\nPasscode: 142239
URL:https://rpm.physics.lbl.gov/event/speaker-josh-dillon-uc-berkeley-title-recent-progress-in-21-cm-cosmology-with-the-hydrogen-epoch-of-reionization-array/
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