© 2026 Copyright held by the owner/author(s).
\nACM acknowledges that this contribution was authored or co-authored by an employee, contractor, or affiliate of the United States government. As such, the United States government retains a nonexclusive, royalty-free right to publish or reproduce this article, or to allow others to do so, for government purposes only. Request permissions from owner/author(s).
\n\nPartial support from the United States DoE (grant numbers DESC0011925, DE-FOA-0002705), NSF (grant numbers PHY240298, PHY2117997), United Kingdom EPSRC (grant numbers UKRI256, EP/V028251/1, EP/N031768/1, EP/S030069/1, and EP/X036006/1), Swiss NSF Grant No. PZ00P2_201594, Schmidt Futures (Grant G23-64934), KIAT, Intel, and AMD is acknowledged. We acknowledge the Caltech Danny Koh graduate student scholarship and the
ETH/Guenther Dissertori partial support for this project.
© 2025 held by the owner/author(s). Publication rights licensed to ACM. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. Copyrights for components of this work owned by others than the author(s) must be honored. Abstracting with credit is permitted. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from permissions@acm.org.
\n\nWe present the performance of centimeter-scale AC-LGAD devices including strip sensors with varying pitch (coarse and narrow), and pixel sensors of varying metal electrode size and geometry. Strip sensors with narrow pitch provide good position reconstruction capabilities, however coarser pitch may offer better cost and performance for applications where channel count or electrical power density should be economized. Pixel sensors with a higher metal area fraction and smaller active thickness provide faster signal risetimes, leading to better time resolution capabilities. We studied the impact of various design parameters on the time and spatial resolution of these sensors and identified the guiding principles for designing sensors optimized for future collider experiments, such as the EIC.
", "date": "2024-11-02", "date_type": "published", "publisher": "IEEE", "place_of_pub": "Piscataway, N.J.", "pagerange": "1-1", "isbn": "9798350388169", "book_title": "2024 IEEE Nuclear Science Symposium (NSS), Medical Imaging Conference (MIC) and Room Temperature Semiconductor Detector Conference (RTSD)", "official_url": "https://authors.library.caltech.edu/records/xsag6-qqh63", "local_group": { "items": [ { "id": "Physics-Department" } ] }, "doi": "10.1109/nss/mic/rtsd57108.2024.10656632", "primary_object": { "basename": "Experimental_survey_of_AC-LGAD_sensor_design_parameters_towards_optimal_4D_tracking_in_collider_experiments.pdf", "url": "https://authors.library.caltech.edu/records/xsag6-qqh63/files/Experimental_survey_of_AC-LGAD_sensor_design_parameters_towards_optimal_4D_tracking_in_collider_experiments.pdf" }, "pub_year": "2024", "author_list": "Apresyan, A.; Dutta, I.; et al." }, { "id": "https://authors.library.caltech.edu/records/vdyf0-v8193", "eprint_status": "archive", "datestamp": "2026-01-17 13:40:42", "lastmod": "2026-03-10 14:41:21", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Apresyan-A", "name": { "family": "Apresyan", "given": "A." }, "orcid": "0000-0002-6186-0130" }, { "id": "Xie-Si", "name": { "family": "Xie", "given": "S." }, "orcid": "0000-0003-2509-5731" }, { "name": { "family": "Chris", "given": "M." } }, { "name": { "family": "Dutta", "given": "I." }, "orcid": "0000-0003-0953-4503" }, { "name": { "family": "Hayrapetyan", "given": "A." }, "orcid": "0000-0002-5674-5154" }, { "name": { "family": "Los", "given": "S." }, "orcid": "0000-0001-8637-5628" }, { "name": { "family": "Pena", "given": "C." }, "orcid": "0000-0002-4500-7930" }, { "name": { "family": "Zimmerman", "given": "T." } } ] }, "title": "Performance of a second generation of the Fermilab Constant Fraction Discriminator ASIC for time-stamping long-strip AC-LGAD sensors.", "ispublished": "pub", "full_text_status": "public", "note": "© 2024 IEEE.
", "abstract": "We present the design and performance characterization results of the second generation of the novel Fermilab Constant Fraction Discriminator ASIC (FCFD) developed to readout AC-coupled low gain avalanche detector (AC-LGAD) sensors. This study presents the performance of the ASIC which was optimized specifically for reading out strip AC-LGAD sensors designed for ePIC experiment at EiC. Performance was measured using charge injection and particle beams with prototype AC-LGAD sensors wirebonded to the FCFD ASIC.", "date": "2024-10-26", "date_type": "published", "publication": "2024 IEEE Nuclear Science Symposium (NSS), Medical Imaging Conference (MIC) and Room Temperature Semiconductor Detector Conference (RTSD)", "publisher": "IEEE", "pagerange": "1-1", "isbn": "979-8-3503-8815-2", "official_url": "https://authors.library.caltech.edu/records/vdyf0-v8193", "local_group": { "items": [ { "id": "CMS@Caltech" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" }, { "id": "Physics-Department" } ] }, "doi": "10.1109/nss/mic/rtsd57108.2024.10658611", "pub_year": "2024", "author_list": "Apresyan, A.; Xie, S.; et al." }, { "id": "https://authors.library.caltech.edu/records/hnmyx-er004", "eprint_status": "archive", "datestamp": "2026-05-20 15:55:02", "lastmod": "2026-05-20 15:58:02", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Kane-Elijah", "name": { "family": "Kane", "given": "Elijah" } }, { "id": "Albert-Chris", "name": { "family": "Albert", "given": "Chris" } }, { "name": { "family": "Cothard", "given": "Nicholas F." }, "orcid": "0000-0002-6151-6292" }, { "id": "Hailey-Dunsheath-S", "name": { "family": "Hailey-Dunsheath", "given": "Steve" }, "orcid": "0000-0002-8504-7988" }, { "id": "Echternach-Pierre-M", "name": { "family": "Echternach", "given": "Pierre M." }, "orcid": "0000-0001-9643-5110" }, { "id": "Foote-Logan", "name": { "family": "Foote", "given": "Logan M." }, "orcid": "0000-0002-4162-8609" }, { "id": "Janssen-Reinier-M-J", "name": { "family": "Janssen", "given": "Reinier M. J." }, "orcid": "0000-0001-9122-9668" }, { "id": "LeDuc-Henry-G", "name": { "family": "LeDuc", "given": "Henry G." }, "orcid": "0000-0002-6721-5271" }, { "id": "Liu-Lun-Jun", "name": { "family": "Liu", "given": "Lun-Jun" }, "orcid": "0009-0004-1270-2373" }, { "id": "Nguyen-Hien-T", "name": { "family": "Nguyen", "given": "Hien T." } }, { "name": { "family": "Glenn", "given": "Jason" }, "orcid": "0000-0001-7527-2017" }, { "id": "Bradford-C-M", "name": { "family": "Bradford", "given": "Charles M." }, "orcid": "0000-0001-5261-7094" }, { "id": "Zmuidzinas-J", "name": { "family": "Zmuidzinas", "given": "Jonas" }, "orcid": "0000-0002-3330-5439" } ] }, "title": "Development of an ultra-sensitive 210-micron array of KIDs for far-IR astronomy", "ispublished": "unpub", "full_text_status": "public", "keywords": "Far-Infrared; Kinetic Inductance Detectors; PRIMA", "note": "© 2024 SPIE.
\n\nThe research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). This work was funded by the NASA (Award No. 141108.04.02.01.36)—to Dr. C. M. Bradford.
\n© 2024 SPIE.
\n\nThe research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). This work was funded by NASA (Award No. 141108.04.02.01.36) to Dr. C. M. Bradford.
\n© 2024 SPIE.
\n\nThe research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). This work was funded by the NASA (Award No. 141108.04.02.01.36)—to Dr. C. M. Bradford. We would like to thank Adrian Sinclair and James Burgoyne for useful discussions on the RFSoC firmware and software, and we would like to thank Chris Groppi’s group at Arizona State University for providing a housing and hardware for the RFSoC. We would also like to thank Bryan Steinbach and Roger O’Brient for helpful discussions about lab infrastructure.
\n© (2024) Society of Photo-Optical Instrumentation Engineers (SPIE).
\n\nKPF was supported by the National Science Foundation under Grant # 2034278, by the Heising-Simons Foundation with grants 2016-042, 2018-0905, & a loan, as well as the Mt. Cuba Astronomical Foundation. KCRM is supported in part by the National Science Foundation under Grant No. AST-1429890. KAPA is supported in part by the National Science Foundation under grant No. AST-1836016. SCALES is supported by the Heising-Simons Foundation, Mt. Cuba Astronomical Foundation, and the National Science foundation under grant No. AST-2216481. Liger is partially supported by the Heising-Simons Foundation, Gordon and Betty Moore Foundation, and by the National Science Foundation under grant No. AST-2308190. HISPEC is supported by the Caltech fund for Keck instrumentation, the Gordon and Betty Moore Foundation, the Heising-Simon Foundation and has benefitted from in-kind contributions from NASA, the AstroBiology Center (NINS), Northwestern, and the University of Toronto. LRIS-2 is supported by the Caltech fund for Keck instrumentation.
\nSome of the data presented herein were obtained at Keck Observatory, which is a private 501(c)3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
\nThis research was carried out, in part, at the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration and funded through the President’s and Director’s Research\\& Development Fund Program.
\nThe authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
", "abstract": "Since the start of science operations in 1993, the twin 10-meter W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact to produce transformative discoveries that keep the U.S. observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships primarily with the Caltech and University of California instrument development teams and through additional collaborations with the University of Notre Dame, the University of Hawaii, Swinburne University of Technology, industry, and other organizations. This paper summarizes the status and performance of observatory infrastructure projects, technology upgrades, and new additions to the suite of observatory instrumentation. We also provide a status of instrumentation projects in early and advanced stages of development that will achieve the goals and objectives summarized in the 2023 Keck Observatory strategic plan. Developed in collaboration with the WMKO science community, the Keck strategic plan sets our sites on 2035 and meets goals identified in the Astro2020 Decadal Survey.", "date": "2024-07-22", "date_type": "published", "publisher": "Society of Photo-Optical Instrumentation Engineers", "place_of_pub": "Bellingham, WA", "isbn": "9781510675155", "book_title": "Ground-based and Airborne Instrumentation for Astronomy X", "editors": { "items": [ { "name": { "family": "Vernet", "given": "Jo\u00ebl R." } }, { "name": { "family": "Bryant", "given": "Julia J." } }, { "name": { "family": "Motohara", "given": "Kentaro" } } ] }, "official_url": "https://authors.library.caltech.edu/records/t3vag-en810", "funders": { "items": [ { "grant_number": "2034278" }, { "grant_number": "2016-042" }, { "grant_number": "2018-0905" }, {}, { "grant_number": "AST-1429890" }, { "grant_number": "AST-2308190" }, {} ] }, "local_group": { "items": [ { "id": "Astronomy-Department" }, { "id": "Palomar-Observatory" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" }, { "id": "Physics-Department" } ] }, "doi": "10.1117/12.3016181", "primary_object": { "basename": "1309606.pdf", "url": "https://authors.library.caltech.edu/records/t3vag-en810/files/1309606.pdf" }, "pub_year": "2024", "author_list": "Kassis, Marc F.; Alvarez, Carlos; et al." }, { "id": "https://authors.library.caltech.edu/records/gn5gn-t9r95", "eprint_status": "archive", "datestamp": "2025-04-09 00:19:13", "lastmod": "2026-03-10 22:28:34", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Gibson-Steven-R", "name": { "family": "Gibson", "given": "Steven R." } }, { "id": "Howard-A-W", "name": { "family": "Howard", "given": "Andrew W." }, "orcid": "0000-0001-8638-0320" }, { "name": { "family": "Rider", "given": "Kodi" } }, { "name": { "family": "Halverson", "given": "Samuel P." } }, { "name": { "family": "Roy", "given": "Arpita" } }, { "id": "Baker-Ashley-D", "name": { "family": "Baker", "given": "Ashley D." }, "orcid": "0000-0002-6525-7013" }, { "name": { "family": "Edelstein", "given": "Jerry" } }, { "name": { "family": "Smith", "given": "Christopher" } }, { "id": "Fulton-Benjamin-J", "name": { "family": "Fulton", "given": "Benjamin" } }, { "name": { "family": "Walawender", "given": "Josh" }, "orcid": "0000-0002-6092-8295" }, { "name": { "family": "Brodheim", "given": "Max" } }, { "name": { "family": "Brown", "given": "Matthew" } }, { "name": { "family": "Chan", "given": "Dwight" } }, { "name": { "family": "Dai", "given": "Fei" } }, { "name": { "family": "Deich", "given": "William" } }, { "name": { "family": "Gottschalk", "given": "Colby" } }, { "name": { "family": "Grillo", "given": "Jason" } }, { "id": "Hale-David", "name": { "family": "Hale", "given": "David" } }, { "name": { "family": "Hill", "given": "Grant" } }, { "name": { "family": "Holden", "given": "Bradford P." }, "orcid": "0000-0002-6153-3076" }, { "name": { "family": "Householder", "given": "Aaron" } }, { "name": { "family": "Isaacson", "given": "Howard" } }, { "name": { "family": "Ishikawa", "given": "Yuzo" } }, { "name": { "family": "Jelinsky", "given": "Sharon" } }, { "name": { "family": "Kassis", "given": "Marc F." } }, { "id": "Kaye-Stephen", "name": { "family": "Kaye", "given": "Stephen" } }, { "id": "Laher-R-R", "name": { "family": "Laher", "given": "Russ" }, "orcid": "0000-0003-2451-5482" }, { "name": { "family": "Lanclos", "given": "Kyle" }, "orcid": "0009-0004-0592-1850" }, { "name": { "family": "Lee", "given": "Chien-Hsiu" }, "orcid": "0000-0003-1700-5740" }, { "name": { "family": "Lilley", "given": "Scott" } }, { "name": { "family": "McCarney", "given": "Benjamin" } }, { "name": { "family": "Miller", "given": "Tim" } }, { "name": { "family": "Payne", "given": "Joel" } }, { "name": { "family": "Petigura", "given": "Erik" } }, { "name": { "family": "Poppett", "given": "Claire" } }, { "name": { "family": "Raffanti", "given": "Mike" } }, { "id": "Rubenzahl-Ryan-Asa", "name": { "family": "Rubenzahl", "given": "Ryan" }, "orcid": "0000-0003-3856-3143" }, { "name": { "family": "Sandford", "given": "Dale" } }, { "name": { "family": "Schwab", "given": "Christian" }, "orcid": "0000-0002-4046-987X" }, { "id": "Shaum-Abby-P", "name": { "family": "Shaum", "given": "Abby P." }, "orcid": "0000-0003-3133-6837" }, { "name": { "family": "Sirk", "given": "Martin M." } }, { "id": "Smith-R-M", "name": { "family": "Smith", "given": "Roger" }, "orcid": "0000-0001-7062-9726" }, { "name": { "family": "Thorne", "given": "Jim" } }, { "name": { "family": "Valliant", "given": "John" } }, { "name": { "family": "Vandenberg", "given": "Adam" } }, { "id": "Wang-Cindy", "name": { "family": "Wang", "given": "Cindy" } }, { "name": { "family": "Wishnow", "given": "Edward" } }, { "name": { "family": "Wold", "given": "Truman" } }, { "name": { "family": "Yeh", "given": "Sherry" }, "orcid": "0000-0002-4037-3114" }, { "name": { "family": "Baca", "given": "Steve" } }, { "id": "Beichman-C-A", "name": { "family": "Beichman", "given": "Charles A." }, "orcid": "0000-0002-5627-5471" }, { "id": "Berriman-Bruce", "name": { "family": "Berriman", "given": "Bruce" }, "orcid": "0000-0001-8388-534X" }, { "name": { "family": "Brown", "given": "Thomas" } }, { "name": { "family": "Casey", "given": "Kelleen" } }, { "name": { "family": "Chin", "given": "Jason" } }, { "name": { "family": "Chong", "given": "James" } }, { "name": { "family": "Cowley", "given": "David" } }, { "name": { "family": "Devenot", "given": "Mark" } }, { "name": { "family": "Elwir", "given": "Hamza" } }, { "name": { "family": "Finstad", "given": "Daniel" } }, { "name": { "family": "Fraysse", "given": "Matthew" } }, { "name": { "family": "James", "given": "Ean" } }, { "name": { "family": "Jhoti", "given": "Elisha" } }, { "name": { "family": "Killian", "given": "Joe" } }, { "name": { "family": "Levine", "given": "Obie" } }, { "name": { "family": "Li", "given": "Adela" } }, { "name": { "family": "Marin", "given": "Eduardo" }, "orcid": "0009-0009-6982-2137" }, { "name": { "family": "Milner", "given": "Steven" } }, { "name": { "family": "Nance", "given": "Craig" } }, { "id": "O'Hanlon-Timothy-J", "name": { "family": "O'Hanlon", "given": "Timothy" } }, { "name": { "family": "Orr", "given": "Daniel" } }, { "name": { "family": "Ortiz-Soto", "given": "Roberto" } }, { "name": { "family": "Payne", "given": "Tom" } }, { "name": { "family": "Pember", "given": "Jacob" } }, { "name": { "family": "Raskin", "given": "Gert" } }, { "name": { "family": "Savage", "given": "Maureen" } }, { "name": { "family": "Seifahrt", "given": "Andreas" } }, { "name": { "family": "Smith", "given": "Brett" } }, { "name": { "family": "Storesund", "given": "Rob" } }, { "name": { "family": "St\u00fcrmer", "given": "Julian" } }, { "name": { "family": "Suominen", "given": "Nick" } }, { "name": { "family": "Tehero", "given": "Jerez" } }, { "name": { "family": "Von Boeckmann", "given": "Tod" } }, { "name": { "family": "Wages", "given": "Keith" } }, { "name": { "family": "Weisfeiler", "given": "Marie" } }, { "name": { "family": "Wilcox", "given": "Mavourneen" } }, { "name": { "family": "Wizinowich", "given": "Peter" }, "orcid": "0000-0002-1646-442X" }, { "name": { "family": "Wolfenberger", "given": "Anna" } } ] }, "title": "System design of the Keck Planet Finder", "ispublished": "unpub", "full_text_status": "public", "keywords": "Spectroscopy; Equipment; Calibration; Design; Planets; Telescopes; Cameras; Charge-coupled devices; Zerodur; Doppler effect", "note": "© (2024) Society of Photo-Optical Instrumentation Engineers (SPIE).
\n\nThe authors thank the Heising-Simons Foundation, the National Science Foundation (award 2034278 through the Mid-Scale Innovations Program in Astronomical Sciences), private donors, the W. M. Keck Foundation, the Simons Foundation, the University of California, Berkeley, the California Institute of Technology, the University of Hawaii, the Jet Propulsion Laboratory, and the Mt. Cuba Astronomical Foundation for support of the KPF project. The authors also thank Winlight Systems for their valuable contributions to the designs of the reformatter and cameras and the DESI project for sharing their camera designs and their expertise with optical fibers. This research was carried out, in part, at the Jet Propulsion Laboratory and the California Institute of Technology under a contract with the National Aeronautics and Space Administration and funded through the President’s and Director’s Research & Development Fund Program.
", "abstract": "The Keck Planet Finder (KPF) is a fiber-fed, high-resolution, echelle spectrometer that specializes in the discovery and characterization of exoplanets using Doppler spectroscopy. In designing KPF, the guiding principles were high throughput to promote survey speed and access to faint targets, and high stability to keep uncalibrated systematic Doppler measurement errors below 30 cm s\u22121. KPF achieves optical illumination stability with a tip-tilt injection system, octagonal cross-section optical fibers, a double scrambler, and active fiber agitation. The optical bench and optics with integral mounts are made of Zerodur to provide thermo-mechanical stability. The spectrometer includes a slicer to reformat the optical input, green and red channels (445\u2013600 nm and 600\u2013870 nm), and achieves a resolving power of \u223c97,000. Additional subsystems include a separate, medium-resolution UV spectrometer (383\u2013402 nm) to record the Ca II H K lines, an exposure meter for real-time flux monitoring, a solar feed for sunlight injection, and a calibration system with a laser frequency comb and etalon for wavelength calibration. KPF was installed and commissioned at the W. M. Keck Observatory in late 2022 and early 2023 and is now in regular use for scientific observations. This paper presents an overview of the as-built KPF instrument and its subsystems, design considerations, and initial on-sky performance.", "date": "2024-07-18", "date_type": "published", "publisher": "Society of Photo-Optical Instrumentation Engineers", "place_of_pub": "Bellingham, WA", "pagerange": "9", "isbn": "9781510675162", "book_title": "Ground-based and Airborne Instrumentation for Astronomy X", "editors": { "items": [ { "name": { "family": "Vernet", "given": "Jo\u00ebl R." } }, { "name": { "family": "Bryant", "given": "Julia J." } }, { "name": { "family": "Motohara", "given": "Kentaro" } } ] }, "official_url": "https://authors.library.caltech.edu/records/gn5gn-t9r95", "funders": { "items": [ {}, { "grant_number": "2034278" }, {}, {}, {}, {}, {}, {}, {} ] }, "local_group": { "items": [ { "id": "Astronomy-Department" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" }, { "id": "Palomar-Observatory" }, { "id": "Physics-Department" } ] }, "doi": "10.1117/12.3017841", "primary_object": { "basename": "1309609.pdf", "url": "https://authors.library.caltech.edu/records/gn5gn-t9r95/files/1309609.pdf" }, "pub_year": "2024", "author_list": "Gibson, Steven R.; Howard, Andrew W.; et al." }, { "id": "https://authors.library.caltech.edu/records/vd45e-v5k40", "eprint_status": "archive", "datestamp": "2024-06-12 17:02:09", "lastmod": "2026-03-10 03:34:20", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Chen-Chi-Fang", "name": { "family": "Chen", "given": "Chi-Fang" }, "orcid": "0000-0001-5589-7896" }, { "id": "Huang-Hsin-Yuan", "name": { "family": "Huang", "given": "Hsin-Yuan" }, "orcid": "0000-0001-5317-2613" }, { "id": "Preskill-J", "name": { "family": "Preskill", "given": "John" }, "orcid": "0000-0002-2421-4762" }, { "id": "Zhou-Leo", "name": { "family": "Zhou", "given": "Leo" }, "orcid": "0000-0001-7598-8621" } ] }, "title": "Local Minima in Quantum Systems", "ispublished": "unpub", "full_text_status": "public", "note": "© 2024 Copyright held by the owner/author(s). This work is licensed under a Creative Commons Attribution 4.0 International License.
\n\nThe authors thank Anurag Anshu, Ryan Babbush, Fernando Brandão, Garnet Chan, Sitan Chen, Soonwon Choi, Jordan Cotler, Jarrod R. McClean, and Mehdi Soleimanifar for their valuable input. HH thanks Patrick Coles, Gavin Crooks, and Faris Sbahi for the inspiring discussions and for sharing their recent works on classical thermodynamics for AI applications [5, 18]. CFC is supported by the AWS Center for Quantum Computing internship. HH is supported by a Google PhD fellowship and a MediaTek Research Young Scholarship. HH acknowledges the visiting associate position at Massachusetts Institute of Technology. LZ acknowledges funding from the Walter Burke Institute for Theoretical Physics at Caltech. JP acknowledges support from the U.S. Department of Energy Of- ce of Science, Oce of Advanced Scientic Computing Research (DE-NA0003525, DE-SC0020290), the U.S. Department of Energy, Oce of Science, National Quantum Information Science Research Centers, Quantum Systems Accelerator, and the National Science Foundation (PHY-1733907). The Institute for Quantum Information and Matter is an NSF Physics Frontiers Center.
", "abstract": "Finding ground states of quantum many-body systems is known to be hard for both classical and quantum computers. As a result, when Nature cools a quantum system in a low-temperature thermal bath, the ground state cannot always be found efficiently. Instead, Nature finds a local minimum of the energy. In this work, we study the problem of finding local minima in quantum systems under thermal perturbations. While local minima are much easier to find than ground states, we show that finding a local minimum is computationally hard for classical computers, even when the task is to output a single-qubit observable at any local minimum. In contrast, we prove that a quantum computer can always find a local minimum efficiently using a thermal gradient descent algorithm that mimics the cooling process in Nature. To establish the classical hardness of finding local minima, we consider a family of two-dimensional Hamiltonians such that any problem solvable by polynomial-time quantum algorithms can be reduced to finding local minima of these Hamiltonians. Therefore, cooling systems to local minima is universal for quantum computation, and, assuming quantum computation is more powerful than classical computation, finding local minima is classically hard and quantumly easy.
\n© 2024 Copyright held by the owner/author(s). This work is licensed under a Creative Commons Attribution 4.0 License.
\n\nThis work was done in part while the authors were visiting the Simons Institute for the Theory of Computing. Y.L. and Z.L. are supported by DOE Grant No. DE-SC0024124, NSF Grant No. 2311733, and DOE Quantum Systems Accelerator. I.K. was supported by funds from the UC Multicampus Research Programs and Initiatives of the University of California, Grant Number M23PL5936. A.A. acknowledges support through the NSF CAREER Award No. 2238836 and NSF award QCIS-FF: Quantum Computing & Information Science Faculty Fellow at Harvard University (NSF 2013303).
", "abstract": "Despite fundamental interests in learning quantum circuits, the existence of a computationally efficient algorithm for learning shallow quantum circuits remains an open question. Because shallow quantum circuits can generate distributions that are classically hard to sample from, existing learning algorithms do not apply. In this work, we present a polynomial-time classical algorithm for learning the description of any unknown n-qubit shallow quantum circuit U (with arbitrary unknown architecture) within a small diamond distance using single-qubit measurement data on the output states of U. We also provide a polynomial-time classical algorithm for learning the description of any unknown n-qubit state | ψ \u27e9 = U | 0n \u27e9 prepared by a shallow quantum circuit U (on a 2D lattice) within a small trace distance using single-qubit measurements on copies of | ψ \u27e9. Our approach uses a quantum circuit representation based on local inversions and a technique to combine these inversions. This circuit representation yields an optimization landscape that can be efficiently navigated and enables efficient learning of quantum circuits that are classically hard to simulate.
\n© 2023 IEEE.
\n\nThis document was prepared using the resources of the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy, Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. This work was also supported by the U.S. Department of Energy under grant DE-SC0012704; used resources of the Center for Functional Nanomaterials, which is a U.S. DOE Office of Science Facility, at Brookhaven National Laboratory under Contract No. DE-SC0012704; supported by the Chilean ANID PIA/APOYO AFB180002 and ANID - Millennium Science Foundation - ICN2019_044. This research was also performed using the resources of the University of Illinois at Chicago and supported by the U.S. Department of Energy under grant DE-FG02-94ER40865.
", "abstract": "© 2023, IEEE.
", "abstract": "We present the low-cost, dual-polarized, wideband quad-ridge choke horn (QRCH) feed with a low-loss dielectric lid optimized for the Deep Synoptic Array (DSA-2000) in radio astronomy. The ridges and dielectric lid allows for a compact feed diameter with small blockage of the 5-meter-diameter axially-symmetric prime-focus reflector. A wide feed pattern suitable for applications with f/D below 0.35 is achieved over the frequency range 0.7-2 GHz. The band-average aperture efficiency in simulation is 66 % in the unshaped reflector including blockage. An extension of the reflector rim reduces the spillover noise contribution to less than 1 K at zenith pointing. Together with an excellent ambient temperature low-noise amplifier developed for DSA-2000 the predicted system noise temperature is 25 K.", "date": "2023-07-23/2023-07-28", "date_type": "published", "publication": "2023 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (USNC-URSI)", "publisher": "IEEE", "place_of_pub": "Piscataway, N. J.", "pagerange": "761-762", "isbn": "9781665442299", "book_title": "2023 IEEE International Symposium on Antennas and Propagation and USNC-URSI Radio Science Meeting (USNC-URSI)", "official_url": "https://authors.library.caltech.edu/records/01fgt-32j85", "local_group": { "items": [ { "id": "Owens-Valley-Radio-Observatory" }, { "id": "Physics-Department" } ] }, "doi": "10.1109/usnc-ursi52151.2023.10237516", "primary_object": { "basename": "Wideband Feed and Reflector Ground Shield for the Deep Synoptic Array (DSA-2000).pdf", "url": "https://authors.library.caltech.edu/records/01fgt-32j85/files/Wideband Feed and Reflector Ground Shield for the Deep Synoptic Array (DSA-2000).pdf" }, "pub_year": "2023", "author_list": "Flygare, Jonas and Woody, David P." }, { "id": "https://authors.library.caltech.edu/records/9qza3-jx928", "eprint_status": "archive", "datestamp": "2026-03-10 17:54:51", "lastmod": "2026-03-28 03:48:57", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Earnshaw-Hannah-P", "name": { "family": "Earnshaw", "given": "Hannah P." }, "orcid": "0000-0001-5857-5622" }, { "id": "Greffe-Timothee", "name": { "family": "Greffe", "given": "Timothee" }, "orcid": "0000-0003-4594-1827" }, { "id": "Smith-R-M", "name": { "family": "Smith", "given": "Roger M." }, "orcid": "0000-0001-7062-9726" }, { "id": "Grefenstette-B-W", "name": { "family": "Grefenstette", "given": "Brian W." }, "orcid": "0000-0002-1984-2932" }, { "id": "Harrison-F-A", "name": { "family": "Harrison", "given": "Fiona A." }, "orcid": "0000-0003-2992-8024" }, { "id": "Hennessy-John-J", "name": { "family": "Hennessy", "given": "John J." }, "orcid": "0000-0002-0135-0219" }, { "id": "Nikzad-Shouleh", "name": { "family": "Nikzad", "given": "Shouleh" }, "orcid": "0009-0004-1255-1018" }, { "id": "Shapiro-Charles-A", "name": { "family": "Shapiro", "given": "Charles A." }, "orcid": "0000-0002-4405-0013" } ] }, "title": "High dynamic range techniques for astronomical applications of CMOS devices", "ispublished": "pub", "full_text_status": "public", "keywords": "CMOS; detectors; algorithms", "note": "© 2022 SPIE.
", "abstract": "We present an approach for improving the effective well depth of a CMOS detector for use on a UV space telescope by using a combination of two techniques: a dual-gain readout mode and the use of a multi-exposure HDR algorithm. Non-destructive readout of the detector in a high-gain and a low-gain mode optimizes the dynamic range of a single exposure by taking advantage of the low read noise of the first mode and the high well depth of the second. The dynamic range can be further extended by the addition of a second, shorter exposure to probe the saturated regions of the initial exposure. We find that, for simulations of an SRI CMOS imager we are testing, its initial sensitivity to ~3 orders of magnitude in flux can be improved to a dynamic range of over 5.5 orders of magnitude (equivalent to a difference of ~14 AB magnitudes) by the combination of a 300 second dual-gain exposure and a 3 second low-gain exposure, with a low overhead in additional read time and computational complexity.
", "date": "2022-08-29", "date_type": "published", "publication": "X-Ray, Optical, and Infrared Detectors for Astronomy X", "publisher": "SPIE", "place_of_pub": "Bellingham, WA", "pagerange": "121910G", "isbn": "9781510653634", "editors": { "items": [ { "name": { "family": "Holland", "given": "Andrew D." } }, { "name": { "family": "Beletic", "given": "James" } } ] }, "official_url": "https://authors.library.caltech.edu/records/9qza3-jx928", "local_group": { "items": [ { "id": "Palomar-Observatory" }, { "id": "Physics-Department" }, { "id": "Space-Radiation-Laboratory" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" } ] }, "doi": "10.1117/12.2630367", "pub_year": "2022", "author_list": "Earnshaw, Hannah P.; Greffe, Timothee; et al." }, { "id": "https://authors.library.caltech.edu/records/13pcq-khj11", "eprint_status": "archive", "datestamp": "2025-04-08 19:22:50", "lastmod": "2026-03-06 21:32:42", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "name": { "family": "Kassis", "given": "Marc ." } }, { "name": { "family": "Allen", "given": "Steve" } }, { "name": { "family": "Alvarez", "given": "Carlos" } }, { "name": { "family": "Banyal", "given": "Ravinder" }, "orcid": "0000-0003-0799-969X" }, { "id": "Bertz-Robert", "name": { "family": "Bertz", "given": "Robert" } }, { "id": "Beichman-C-A", "name": { "family": "Beichman", "given": "Charles" }, "orcid": "0000-0002-5627-5471" }, { "name": { "family": "Brown", "given": "Aaron" } }, { "name": { "family": "Brown", "given": "Matthew" } }, { "name": { "family": "Cabak", "given": "Gerald" } }, { "name": { "family": "Bundy", "given": "Kevin" } }, { "name": { "family": "Cetre", "given": "Sylvain" } }, { "name": { "family": "Chin", "given": "Jason" } }, { "name": { "family": "Chun", "given": "Mark" } }, { "name": { "family": "Deich", "given": "Will" } }, { "id": "Dekany-Richard", "name": { "family": "Dekany", "given": "Richard" }, "orcid": "0000-0002-5884-7867" }, { "name": { "family": "Delorme", "given": "Jacques-Robert" }, "orcid": "0000-0001-8953-1008" }, { "name": { "family": "Devenot", "given": "Mark" } }, { "name": { "family": "Doppmann", "given": "Greg" } }, { "name": { "family": "Fitzgerald", "given": "Michael P." }, "orcid": "0000-0002-0176-8973" }, { "id": "Fucik-Jason-R", "name": { "family": "Fucik", "given": "Jason R." } }, { "name": { "family": "Hill", "given": "Grant" } }, { "name": { "family": "Hinz", "given": "Philip ." } }, { "name": { "family": "Holden", "given": "Bradford P." }, "orcid": "0000-0002-6153-3076" }, { "id": "Howard-A-W", "name": { "family": "Howard", "given": "Andrew W." }, "orcid": "0000-0001-8638-0320" }, { "id": "Gao-Maodong", "name": { "family": "Gao", "given": "Maodong" } }, { "id": "Gibson-Steve", "name": { "family": "Gibson", "given": "Steve" } }, { "name": { "family": "Gomez", "given": "Percy" }, "orcid": "0000-0003-0408-9850" }, { "name": { "family": "Gottschalk", "given": "Colby" } }, { "name": { "family": "Gillingham", "given": "Peter R." } }, { "name": { "family": "Jones", "given": "Tucker" } }, { "id": "Jovanovic-N", "name": { "family": "Jovanovic", "given": "Nemanja" }, "orcid": "0000-0001-5213-6207" }, { "name": { "family": "Kirby", "given": "Evan" } }, { "name": { "family": "Konopacky", "given": "Quinn" }, "orcid": "0000-0002-9936-6285" }, { "name": { "family": "Krishnan", "given": "Shanti" } }, { "name": { "family": "Kupke", "given": "Renate" }, "orcid": "0000-0002-5826-5314" }, { "name": { "family": "Larkin", "given": "James E." } }, { "name": { "family": "Leifer", "given": "Stephanie D." }, "orcid": "0000-0002-8980-7825" }, { "name": { "family": "Lewis", "given": "Hilton A." } }, { "name": { "family": "Lilley", "given": "Scott" } }, { "name": { "family": "Lu", "given": "Jessica" } }, { "name": { "family": "Lyke", "given": "James E." } }, { "name": { "family": "MacDonald", "given": "Nicholas" } }, { "name": { "family": "Marin", "given": "Eduardo" }, "orcid": "0009-0009-6982-2137" }, { "id": "Matuszewski-Matt", "name": { "family": "Matuszewski", "given": "Matt" } }, { "id": "Mawet-D", "name": { "family": "Mawet", "given": "Dimitri" }, "orcid": "0000-0002-8895-4735" }, { "name": { "family": "McGurk", "given": "Rosalie" }, "orcid": "0000-0003-2064-4105" }, { "id": "Millar-Blanchaer-M-A", "name": { "family": "Millar-Blanchaer", "given": "Maxwell A." }, "orcid": "0000-0001-6205-9233" }, { "id": "Nash-Reston-B", "name": { "family": "Nash", "given": "Reston B." } }, { "name": { "family": "Nance", "given": "Craig" } }, { "id": "Neill-James-D", "name": { "family": "Neill", "given": "James D." }, "orcid": "0000-0002-0466-1119" }, { "name": { "family": "O'Meara", "given": "John M." }, "orcid": "0000-0002-7893-1054" }, { "name": { "family": "Peretz", "given": "Eliad" } }, { "name": { "family": "Poppett", "given": "Claire ." } }, { "name": { "family": "Mather", "given": "John C." } }, { "name": { "family": "Radovan", "given": "Matthew V." } }, { "id": "Roberts-Mitsuko-K", "name": { "family": "Roberts", "given": "Mitsuko K." } }, { "name": { "family": "Ragland", "given": "Sam" }, "orcid": "0000-0002-0696-1780" }, { "name": { "family": "Rider", "given": "Kodi" } }, { "name": { "family": "Rockosi", "given": "Constance ." }, "orcid": "0000-0002-6667-7028" }, { "name": { "family": "Sandfor", "given": "Dale" } }, { "id": "Shen-Boqiang", "name": { "family": "Shen", "given": "Boqiang" } }, { "id": "Steidel-C-C", "name": { "family": "Steidel", "given": "Charles C." }, "orcid": "0000-0002-4834-7260" }, { "name": { "family": "Simha", "given": "Sunil" }, "orcid": "0000-0003-3801-1496" }, { "name": { "family": "Skemer", "given": "Andy" } }, { "name": { "family": "Stelter", "given": "Richard" }, "orcid": "0000-0003-4549-0210" }, { "name": { "family": "Surendran", "given": "Avinash" }, "orcid": "0000-0003-0897-7759" }, { "name": { "family": "Thorne", "given": "James" } }, { "name": { "family": "McCarney", "given": "Ben" } }, { "name": { "family": "Lanclos", "given": "Kyle" }, "orcid": "0009-0004-0592-1850" }, { "id": "Baker-Ashley", "name": { "family": "Baker", "given": "Ashley" }, "orcid": "0000-0002-6525-7013" }, { "id": "Rubenzahl-Ryan-Asa", "name": { "family": "Rubenzahl", "given": "Ryan" }, "orcid": "0000-0003-3856-3143" }, { "name": { "family": "Roy", "given": "Arpita" }, "orcid": "0000-0001-8127-5775" }, { "name": { "family": "Halverson", "given": "Sam" } }, { "name": { "family": "Edelstein", "given": "Jerry" } }, { "id": "Martin-D-Christopher", "name": { "family": "Martin", "given": "Christopher" }, "orcid": "0000-0002-8650-1644" }, { "name": { "family": "Savage", "given": "Maureen" } }, { "name": { "family": "Sandford", "given": "Dale" } }, { "name": { "family": "Sallum", "given": "Stephanie" }, "orcid": "0000-0001-6871-6775" }, { "name": { "family": "Walawender", "given": "Josh" }, "orcid": "0000-0002-6092-8295" }, { "name": { "family": "Wizinowich", "given": "Peter" }, "orcid": "0000-0002-1646-442X" }, { "name": { "family": "Westfall", "given": "Kyle B." }, "orcid": "0000-0003-1809-6920" }, { "id": "Vahala-K-J", "name": { "family": "Vahala", "given": "Kerry J." }, "orcid": "0000-0003-1783-1380" }, { "name": { "family": "Wright", "given": "Shelley A." }, "orcid": "0000-0003-1034-8054" }, { "name": { "family": "Wold", "given": "Truman" } }, { "name": { "family": "Yeh", "given": "Sherry" }, "orcid": "0000-0002-4037-3114" } ] }, "title": "Innovations and advances in instrumentation at the W. M. Keck Observatory, vol. II", "ispublished": "unpub", "full_text_status": "public", "keywords": "Adaptive optics; Spectrographs; Exoplanets; Sensors; Spectroscopy; Imaging systems; Planets; Telescopes; Cameras; Observatories", "note": "© (2022) Society of Photo-Optical Instrumentation Engineers (SPIE).
\n\nKPF was supported by the National Science Foundation under Grant # 2034278, by the Heising-Simons Foundation with grants 2016-042, 2018-0905, & a loan, as well as the Mt. Cuba Astronomical Foundation. KCRM is supported in part by the National Science Foundation under Grant No. AST-1429890. KAPA is supported in part by the National Science Foundation under grant No. AST-1836016. SCALES and Liger are partially supported by the Heising-Simons Foundation. HISPEC is partially funded by the Gordon and Betty Moore Foundation.
\nThe W. M. Keck Observatory is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
\nThe authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
", "abstract": "Since the start of science operations in 1993, the twin 10-meter W. M. Keck Observatory (WMKO) telescopes have continued to maximize their scientific impact and to produce transformative discoveries that keep the observing community on the frontiers of astronomical research. Upgraded capabilities and new instrumentation are provided though collaborative partnerships with Caltech, the University of California, and the University of Hawaii instrument development teams, as well as industry and other organizations. This paper summarizes the performance of recently commissioned infrastructure projects, technology upgrades, and new additions to the suite of observatory instrumentation. We also provide a status of projects currently in design or development phases and, since we keep our eye on the future, summarize projects in exploratory phases that originate from our 2022 strategic plan developed in collaboration with our science community to adapt and respond to evolving science needs.", "date": "2022-08-29", "date_type": "published", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_pub": "Bellingham, Washington", "book_title": "Ground-based and Airborne Instrumentation for Astronomy IX", "editors": { "items": [ { "name": { "family": "Evans", "given": "Christopher J." } }, { "name": { "family": "Bryant", "given": "Julia J." } }, { "name": { "family": "Motohara", "given": "Kentaro" } } ] }, "official_url": "https://authors.library.caltech.edu/records/13pcq-khj11", "funders": { "items": [ { "grant_number": "2034278" }, { "grant_number": "2016-042" }, { "grant_number": "2018-0905" }, { "grant_number": "AST-1429890" }, {}, {} ] }, "local_group": { "items": [ { "id": "Astronomy-Department" }, { "id": "Palomar-Observatory" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" }, { "id": "Physics-Department" } ] }, "doi": "10.1117/12.2628630", "primary_object": { "basename": "1218405.pdf", "url": "https://authors.library.caltech.edu/records/13pcq-khj11/files/1218405.pdf" }, "pub_year": "2022", "author_list": "Kassis, Marc .; Allen, Steve; et al." }, { "id": "https://authors.library.caltech.edu/records/h2hbk-2bm48", "eprint_status": "archive", "datestamp": "2026-03-24 18:27:45", "lastmod": "2026-03-28 03:48:52", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Gabritchidze-Bekari", "name": { "family": "Gabritchidze", "given": "Bekari" }, "orcid": "0000-0001-6392-0523" }, { "id": "Cleary-K-A", "name": { "family": "Cleary", "given": "Kieran" }, "orcid": "0000-0002-8214-8265" }, { "id": "Kooi-Jacob", "name": { "family": "Kooi", "given": "Jacob" }, "orcid": "0000-0002-6610-0384" }, { "id": "Esho-Iretomiwa", "name": { "family": "Esho", "given": "Iretomiwa" }, "orcid": "0000-0002-3746-6571" }, { "id": "Readhead-A-C-S", "name": { "family": "Readhead", "given": "Anthony C." }, "orcid": "0000-0001-9152-961X" }, { "id": "Minnich-A-J", "name": { "family": "Minnich", "given": "Austin J." }, "orcid": "0000-0002-9671-9540" } ] }, "title": "Experimental Characterization of Temperature-Dependent Microwave Noise of Discrete HEMTs: Drain Noise and Real-Space Transfer", "ispublished": "pub", "full_text_status": "public", "keywords": "HEMTs; microwave measurements; cryogenics; low-noise amplifiers; drain temperature; real-space transfer", "note": "© 2022 IEEE.
\n\nThe authors thank Sander Weinreb, Pekka Kangaslahti, James Lamb, Shi Jun, Junjie Li and Jan Grahn for useful
discussions.
This work was supported by the National Science Foundation under Grant No. 1911220.
", "abstract": "We report wafer characterization of the S-parameters and microwave noise temperature of discrete GaAs and GaN HEMTs over a temperature range of 20 - 300 K. The measured noise temperature (T50) exhibits a dependence on physical temperature that is inconsistent with a constant drain temperature, with Td for the GaAs and GaN devices changing from ~ 2000 K and ~2800 K at room temperature to ~ 700 K and ~ 1800 K at cryogenic temperatures, respectively. The observed temperature dependence is qualitatively consistent with that predicted from a theory of drain noise based on real-space transfer of electrons from the channel to the barrier.
", "date": "2022-06-19", "date_type": "published", "publication": "2022 IEEE/MTT-S International Microwave Symposium - IMS 2022", "publisher": "IEEE", "pagerange": "615-618", "isbn": "978-1-6654-9613-1", "official_url": "https://authors.library.caltech.edu/records/h2hbk-2bm48", "funders": { "items": [ { "grant_number": "1911220" } ] }, "local_group": { "items": [ { "id": "Owens-Valley-Radio-Observatory" }, { "id": "Division-of-Physics-Mathematics-and-Astronomy" }, { "id": "Physics-Department" }, { "id": "Astronomy-Department" }, { "id": "Division-of-Engineering-and-Applied-Science" }, { "id": "Kavli-Nanoscience-Institute" } ] }, "doi": "10.1109/ims37962.2022.9865505", "pub_year": "2022", "author_list": "Gabritchidze, Bekari; Cleary, Kieran; et al." }, { "id": "https://authors.library.caltech.edu/records/37vnq-w7y82", "eprint_id": 94084, "eprint_status": "archive", "datestamp": "2023-08-19 15:07:41", "lastmod": "2026-03-06 22:24:18", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bernardi-Marco", "name": { "family": "Bernardi", "given": "Marco" }, "orcid": "0000-0001-7289-9666" } ] }, "title": "Ab initio charge carrier dynamics and its application to materials for energy", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2019 American Chemical Society.", "abstract": "This talk will discuss novel first-principles calcns. of charge carrier dynamics, which are broadly applicable to materials employed in renewable energy devices. Calcns. of charge transport and ultrafast dynamics have relied on heuristic approaches for the past several decades. Recent progress in combining d. functional theory and related methods with kinetic equations, such as the Boltzmann transport equation (BTE), are enabling spectacular advances in computing carrier dynamics in materials from first principles. A special role is played by the interaction between charge carriers and\nlattice vibrations, also known as the electron-phonon (e-ph) interaction, which dominates carrier dynamics near room temp. and at energies within a few eV of the band gap. We will discuss our recently developed methods to compute e-ph scattering processes from first principles, and show how these developments enable accurate calcns. of charge transport and ultrafast dynamics in materials, including: 1) Accurate calcns. of the electron mobility, leading to new insight into charge transport in polar semiconductors, perovskite oxides, and org. materials. We will also touch briefly on the computation of charge transport in the polaron regime. 2) The ultrafast dynamics of excited (so-called \"hot\") carriers, with application to lighting devices, solar energy conversion, and ultrafast spectroscopy. A new parallel algorithm to propagate in time the BTE for excited electrons and coupled electrons and phonons will be presented. A recent extension to include the elec. field in the BTE and accurately compute velocity-field curves in semiconductors will also be discussed. The talk will close with a discussion of PERTURBO, an open source code we are developing to make these calcns. available to the community.", "date": "2019-04", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20190325-081733515", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190325-081733515", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Physics-Department" } ] }, "pub_year": "2019", "author_list": "Bernardi, Marco" }, { "id": "https://authors.library.caltech.edu/records/ba6jw-48h04", "eprint_id": 94095, "eprint_status": "archive", "datestamp": "2023-08-19 15:08:54", "lastmod": "2026-03-17 23:39:12", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Jeon-Taeyoon", "name": { "family": "Jeon", "given": "Taeyoon" } }, { "id": "Nateghi-A", "name": { "family": "Nateghi", "given": "Amirhossein" } }, { "id": "Scherer-A", "name": { "family": "Scherer", "given": "Axel" }, "orcid": "0000-0002-2160-9064" } ] }, "title": "Portable high speed mid-IR spectrometer", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2019 American Chemical Society.", "abstract": "The absorption spectra of mols. in the mid-IR (mid-IR) region are used for mol. anal., and the 5-15m wavelength range is sometimes called the fingerprint region, as it enables specific identification of mols. Mol. anal. using a mid-IR light source is typically performed using a Fourier-Transform IR Spectroscopy (FTIR) system. The delicate and complex optical alignment of such instruments limits the miniaturization of mid-IR spectrometers and increases the cost and size of the spectrometer. To solve this problem, we have developed a more robust spectrometer that combines a thermal imaging camera with a hyperspectral filter. This Fabry-Perot filter consists of two high-reflectivity Si/air mirrors that are assembled with a slight angle, so that the gradual change in the cavity gap between the two mirrors changes the resonant frequency of the filter. The variable filter disperses the broadband mid-IR light source to different frequencies, each assigned to a different pixel in the microbolometer array. The high refractive index contrast between silicon and air provides a large free spectral range, wide enough to cover a detection range of from 7 mm to 14 mm. By using a com.\nthermal imaging camera as detector and a Diesel engine glow plug as a source, we have demonstrated an inexpensive and robust spectrometer with no moving parts and rapid spectral acquisition. We present absorption spectra of various types of polymers, biomols. and drugs in the mid-IR region, obtained within 1 s, and compare these to spectra acquired with a conventional FTIR system.", "date": "2019-04", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20190325-090414166", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190325-090414166", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Physics-Department" } ] }, "pub_year": "2019", "author_list": "Jeon, Taeyoon; Nateghi, Amirhossein; et al." }, { "id": "https://authors.library.caltech.edu/records/efbv0-spd20", "eprint_id": 94083, "eprint_status": "archive", "datestamp": "2023-08-19 15:07:35", "lastmod": "2026-03-06 22:24:49", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bernardi-Marco", "name": { "family": "Bernardi", "given": "Marco" }, "orcid": "0000-0001-7289-9666" } ] }, "title": "Advances in ab initio calculations of light-matter interaction in two-dimensional transition metal dichalcogenides", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2019 American Chemical Society.", "abstract": "Two-dimensional (2D) transition metal dichalcogenides (TMDs) exhibit unusual electronic and optical properties. This talk will discuss novel first-principles calcns. of light absorption and emission in 2D-TMDs. First, we will show that visible light absorption per unit thickness in monolayer and few-layer TMDs is 1-2 orders of magnitudes greater than in conventional bulk semiconductors, and discuss application of TMDs to solar energy conversion. We will then introduce a formalism combining the ab initio Bethe-Salpeter equation with Fermi's golden rule to investigate light emission in 2DTMDs. We will show calcns. of the radiative lifetimes as a function of temp. in 2D-TMDs, which are in excellent\nagreement with expt. and provide new microscopic insights into exciton recombination in monolayers and heterobilayers. We will also address the anisotropic photoluminescence seen exptl. upon exciting TMDs with linearly polarized light. We generalize our radiative lifetime calcns. to obtain an equation for light emission as a function of angle and polarization, and show the presence of an inherently anisotropic photoluminescence due to the valley degeneracy of the lowest bright excitons. In closing, we will discuss our recent efforts on computing exciton-phonon interactions from first principles, and how these calcns. allow us to investigate nonequil. exciton dynamics in photoexcited 2D-TMDs.", "date": "2019-04", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20190325-081503026", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190325-081503026", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Physics-Department" } ] }, "pub_year": "2019", "author_list": "Bernardi, Marco" }, { "id": "https://authors.library.caltech.edu/records/50shv-sxf21", "eprint_id": 85772, "eprint_status": "archive", "datestamp": "2023-08-19 08:02:40", "lastmod": "2026-03-18 16:01:30", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Bagley-J-D", "name": { "family": "Bagley", "given": "Jacob" } }, { "id": "Hsu-Chen-Chih", "name": { "family": "Hsu", "given": "Chen-Chih" } }, { "id": "Tseng-Wei-Shiuan", "name": { "family": "Tseng", "given": "Wei-Shiuan" } }, { "id": "Teague-M-L", "name": { "family": "Teague", "given": "Marcus" } }, { "id": "Yeh-Nai-Chang", "name": { "family": "Yeh", "given": "Nai-Chang" }, "orcid": "0000-0002-1826-419X" } ] }, "title": "High yield bottom-up PECVD synthesis of graphene nanoribbons and their application in supercapacitors", "ispublished": "unpub", "full_text_status": "restricted", "note": "\u00a9 2018 American Chemical Society.", "abstract": "Increasing global energy demands and climate change concerns related to energy use require developing\nenduring and efficient energy technologies. Supercapacitors could significantly contribute to energy technol. in\nthis respect due to their long cycle life and rapid charge/discharge capabilities. However, supercapacitors suffer\nfrom poor energy d. which severely limits their application. Because supercapacitors store energy capacitively at\nelectrode surfaces, one obvious strategy to improve energy d. is to use high surface area and high capacitance\nelectrode materials. Graphene nanoribbons, long and narrow strips of graphene, are a promising\nsupercapacitor electrode material due to (i) good elec. cond., (ii) high surface area as a two-dimensional\nmaterial, and (iii) abundant edges which have enhanced capacitance compared to the graphene basal plane.\nCurrent graphene nanoribbon fabrication procedures are either unscalable or incorporate polymer and/or\nmetal contaminants, but we have developed a high yield bottom-up PECVD synthesis of high quality\ngraphene nanoribbons. Deposition takes place at ca. 500 mTorr in a 0.5 in. (outer diam.) quartz tube on\ncopper foil in a hydrogen/methane plasma with 1,2-dichlorobenzene precursor. Graphene nanoribbon growth\nbegins as benzene radicals seed onto copper foil, and arom./methane carbon species propagate growth.\nCharacterization confirms the synthesis of graphene nanoribbons. Raman spectroscopy measurements show\nG and 2D peaks corresponding to graphene structure and a strong D peak corresponding to graphene edge\nstates. UPS measurements reveal a work function of 4.45 eV compared to 4.5 eV for pristine graphene. EDS\nand SAD measurements in a TEM confirm at. purity and a hexagonal lattice consistent with graphene. Finally,\nSEM images demonstrate high aspect ratios with widths less than 500 nm and lengths greater than 5 \u03bcm.\nAlthough these graphene nanoribbons are too wide for many applications, this represents a starting point for\ndeveloping a very large scale integrable synthesis of graphene nanoribbons as we are able to produce\ngraphene nanoribbons at a rate of 0.05 mg/cm2/min. Graphene nanoribbons have been characterized for\nsupercapacitor application and demonstrate excellent power and energy densities.", "date": "2018-03", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20180412-074132598", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180412-074132598", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Physics-Department" } ] }, "pub_year": "2018", "author_list": "Bagley, Jacob; Hsu, Chen-Chih; et al." }, { "id": "https://authors.library.caltech.edu/records/v3h2x-fjf61", "eprint_id": 99541, "eprint_status": "archive", "datestamp": "2023-08-19 00:43:35", "lastmod": "2026-03-06 22:24:55", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Agapito-L-A", "name": { "family": "Agapito", "given": "Luis" } }, { "id": "Zhou-Jin-Jian", "name": { "family": "Zhou", "given": "Jin-Jian" }, "orcid": "0000-0002-1182-9186" }, { "id": "Jhalani-V-A", "name": { "family": "Jhalani", "given": "Vatsal" }, "orcid": "0000-0003-0866-0858" }, { "id": "Bernardi-Marco", "name": { "family": "Bernardi", "given": "Marco" }, "orcid": "0000-0001-7289-9666" } ] }, "title": "PERTURBO: A software platform for accelerated discovery of\n microscopic processes in materials", "ispublished": "unpub", "full_text_status": "public", "note": "Published - 2017_nsf_see_poster_high.pdf
", "abstract": "Solid-state technologies depend crucially on charge\ncarrier scattering and dynamics. Charge carriers are\nscattered by quasiparticles and excitations in materials\n(e.g. phonons, defects, photons, electrons, holes, etc.)\n\nPERTURBO is a robust platform to study these\nelectron scattering processes using first-principles\ncalculations and many-body perturbation theory.\nPERTURBO fills a void in the software ecosystem to\ndesign advanced materials, and will foster scientific\nand technological innovation.\n\nPERTURBO combines new computational methods\ndeveloped in our group. The code implementation\nadopts modern programming practices (HDF5,\nversion control, MPI/OpenMP) and will be distributed\nunder the standard open GPL license.", "date": "2017", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20191029-132109124", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191029-132109124", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NSF" }, { "agency": "Natural Sciences and Engineering Research Council of Canada (NSERC)" } ] }, "local_group": { "items": [ { "id": "Physics-Department" } ] }, "primary_object": { "basename": "2017_nsf_see_poster_high.pdf", "url": "https://authors.library.caltech.edu/records/v3h2x-fjf61/files/2017_nsf_see_poster_high.pdf" }, "pub_year": "2017", "author_list": "Agapito, Luis; Zhou, Jin-Jian; et al." }, { "id": "https://authors.library.caltech.edu/records/383dc-rxz56", "eprint_id": 64971, "eprint_status": "archive", "datestamp": "2023-08-19 01:51:17", "lastmod": "2026-03-18 04:28:34", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Groppi-C", "name": { "family": "Groppi", "given": "Christopher" } }, { "id": "Walker-C-C", "name": { "family": "Walker", "given": "Christopher" } }, { "id": "Kulesa-C", "name": { "family": "Kulesa", "given": "Craig" } }, { "id": "Golish-D", "name": { "family": "Golish", "given": "Dathon" } }, { "id": "Kloosterman-J", "name": { "family": "Kloosterman", "given": "Jenna" } }, { "id": "Weinreb-S", "name": { "family": "Weinreb", "given": "Sander" }, "orcid": "0000-0002-9353-6204" }, { "id": "Jones-G", "name": { "family": "Jones", "given": "Glenn" } }, { "id": "Bardin-J-C", "name": { "family": "Bardin", "given": "Joseph" }, "orcid": "0000-0002-6523-6730" }, { "id": "Mani-H", "name": { "family": "Mani", "given": "Hamdi" } }, { "id": "Kuiper-T", "name": { "family": "Kuiper", "given": "Tom" } }, { "id": "Kooi-J-W", "name": { "family": "Kooi", "given": "Jacob" }, "orcid": "0000-0002-6610-0384" }, { "id": "Lichtenberger-A", "name": { "family": "Lichtenberger", "given": "Art" } }, { "id": "Cecil-T", "name": { "family": "Cecil", "given": "Thomas" } }, { "id": "Puetz-P", "name": { "family": "Puetz", "given": "Patrick" } }, { "id": "Narayanan-G", "name": { "family": "Narayanan", "given": "Gopal" } }, { "id": "Hedden-A", "name": { "family": "Hedden", "given": "Abigail" } } ] }, "title": "Test and integration results from SuperCam: a 64-pixel array receiver for the 350 GHz atmospheric window", "ispublished": "unpub", "full_text_status": "public", "note": "\u00a9 2010 Associated Universities, Inc.\n\nPublished - testingintegrationsupercam.pdf
", "abstract": "We report on laboratory testing and telescope integration of SuperCam, a 64 pixel imaging spectrometer designed for operation in the astrophysically important 870 micron atmospheric window. SuperCam will be used to answer fundamental questions about the physics and chemistry of molecular clouds in the Galaxy and their direct relation to star and planet formation. The Supercam key project is a fully sampled Galactic plane survey covering over 500 square degrees of the Galaxy in ^(12)CO(3-2) and ^(13)CO(3-2) with 0.3 km/s velocity resolution. \n\nSuperCam will have several times more pixels than any existing spectroscopic imaging array at submillimeter wavelengths. The exceptional mapping speed that will result, combined with the efficiency and angular resolution provided by the HHT will make SuperCam a powerful instrument for probing the history of star formation in our Galaxy and nearby galaxies. SuperCam will be used to answer fundamental questions about the physics and chemistry of molecular clouds in the Galaxy and their direct relation to star and planet formation. Through Galactic surveys, particularly in CO and its isotopomers, the impact of Galactic environment on these phenomena will be realized. These studies will serve as \"finder charts\" for future focused research (e.g. with ALMA) and markedly improve the interpretation, and enhance the value of numerous\ncontemporary surveys. \n\nIn the past, all heterodyne focal plane arrays have been constructed using discrete mixers, arrayed in the focal plane. SuperCam reduces cryogenic and mechanical complexity by integrating multiple mixers and amplifiers into a single array module with a single set of DC and IF connectors. These modules are housed in a closed-cycle cryostat with a 1.5W capacity 4K cooler. The Supercam instrument is currently undergoing laboratory testing with four of the eight mixer array modules installed in the cryostat (32 pixels). Work is now underway to perform the necessary modifications at the 10m Heinrich Hertz Telescope to accept the Supercam system. Supercam will be installed in the cassegrain cabin of the HHT, including the optical system, IF processing, spectrometers and control electronics. Supercam will be integrated with the HHT during the 2009-2010 observing season with 32 pixels installed. The system will be upgraded to 64 pixels during the summer of 2010 after assembly of the four additional mixer modules is completed.", "date": "2010-03", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20160302-153850079", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160302-153850079", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "local_group": { "items": [ { "id": "Keck-Institute-for-Space-Studies" }, { "id": "Physics-Department" } ] }, "primary_object": { "basename": "testingintegrationsupercam.pdf", "url": "https://authors.library.caltech.edu/records/383dc-rxz56/files/testingintegrationsupercam.pdf" }, "pub_year": "2010", "author_list": "Groppi, Christopher; Walker, Christopher; et al." }, { "id": "https://authors.library.caltech.edu/records/0y30s-8r716", "eprint_id": 55548, "eprint_status": "archive", "datestamp": "2023-08-19 07:02:00", "lastmod": "2026-03-18 04:47:26", "type": "conference_item", "metadata_visibility": "show", "creators": { "items": [ { "id": "Cohen-C-M-S", "name": { "family": "Cohen", "given": "C. M. S." }, "orcid": "0000-0002-0978-8127" }, { "id": "Mewaldt-R-A", "name": { "family": "Mewaldt", "given": "R. A." }, "orcid": "0000-0003-2178-9111" }, { "id": "Christian-E-R", "name": { "family": "Christian", "given": "E. R." }, "orcid": "0000-0003-2134-3937" }, { "id": "Cummings-A-C", "name": { "family": "Cummings", "given": "A. C." }, "orcid": "0000-0002-3840-7696" }, { "id": "Leske-R-A", "name": { "family": "Leske", "given": "R. A." }, "orcid": "0000-0002-0156-2414" }, { "id": "Slocum-P-L", "name": { "family": "Slocum", "given": "P. L." } }, { "id": "Stone-E-C", "name": { "family": "Stone", "given": "E. C." }, "orcid": "0000-0002-2010-5462" }, { "id": "von-Rosenvinge-T-T", "name": { "family": "von Rosenvinge", "given": "T. T." } }, { "id": "Wiedenbeck-M-E", "name": { "family": "Wiedenbeck", "given": "M. E." }, "orcid": "0000-0002-2825-3128" } ] }, "title": "Examining the Abundance of Rare Elements in Solar Energetic Particle Events", "ispublished": "unpub", "full_text_status": "public", "note": "This work was supported by NASA aL Caltech (under grant NAG5-6912), Jet Propulsion Laboratory, aod Goddard\nSpace Flight Center.", "abstract": "Using data accumulated with the Solar Isotope Spectrometer on ACE during 27 large solar energetic pa1ticle (SEP) events the effects of charge-to-mass (Q/M) fractionation\non rare elements arc examined. In an attempt to correct for these fractionation effects and obtain preliminary\nestimates of the coronal abundances of K, Ti, Cr, Mn, Co, Ni, Cu, and Zn, the SEP events are classified according to their Fe/Si ratio. The data from all events within an Fe/Si category are summed and the rare element abundances extracted over an energy interval of 20 to 65 MeV/nucleon. We estimated the apparent Q/M fractionation, corrected for it, and obtained initial results which are encouraging.", "date": "2001", "date_type": "published", "publisher": "Caltech Library", "id_number": "CaltechAUTHORS:20150305-131051186", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150305-131051186", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "NASA", "grant_number": "NAG5-6912" } ] }, "other_numbering_system": { "items": [ { "id": "2003-02", "name": "Space Radiation Laboratory" } ] }, "local_group": { "items": [ { "id": "Space-Radiation-Laboratory" }, { "id": "Physics-Department" } ] }, "primary_object": { "basename": "2003-02.pdf", "url": "https://authors.library.caltech.edu/records/0y30s-8r716/files/2003-02.pdf" }, "pub_year": "2001", "author_list": "Cohen, C. M. S.; Mewaldt, R. A.; et al." } ]