November 2023 - Qse-grad-students

[QMatter in Math/Physics 2023 Nov 7, Tue 4:30 - 6 pm] Cameron Krulewski (MIT) & Leon Liu (Harvard) A Long Exact Sequence in Symmetry Breaking - Harvard CMSA G10

by Juven Wang

Please circulate! There will be NO seminar on Friday due to it being (pre-)Veterans Day. Quantum Matter in Mathematics and Physics (QMMP) 2023: https://cmsa.fas.harvard.edu/event_category/quantum-matter-seminar/ ----- This seminar will be in person! *Time: *Nov 7, Tue 4:30 - 6 pm* ET* *Location: Harvard CMSA G10* Zoom: https://harvard.zoom.us/j/977347126 Password: cmsa ————————————————————————————————— Speaker: Cameron Krulewski (MIT) and Leon Liu (Harvard) Title: A Long Exact Sequence in Symmetry Breaking Abstract: We study defects in symmetry breaking phases, such as domain walls, vortices, and hedgehogs. In particular, we focus on the localized gapless excitations that sometimes occur at the cores of these objects. These are topologically protected by an ’t Hooft anomaly. We classify different symmetry breaking phases in terms of the anomalies of these defects and relate them to the anomaly of the broken symmetry by an anomaly-matching formula. We also derive the obstruction to the existence of a symmetry breaking phase with a local defect. We obtain these results using a long exact sequence of groups of invertible field theories, which we call the “symmetry breaking long exact sequence” (SBLES). The mathematical backbone of the SBLES is the Smith homomorphism, which gives a family of maps between twisted bordism groups. Though many examples have been studied, we give the first completely general account of the Smith homomorphism. We lift it to a map of Thom spectra and identify the cofiber, producing a long exact sequence of twisted bordism groups; the SBLES is the Anderson dual of that long exact sequence. Our work develops further the theory of higher Berry phase and its bulk-boundary correspondence and serves as a new computational tool for classifying symmetry protected topological phases. -------- Subscribe to Harvard CMSA Quantum Matter and other seminar videos (more to be uploaded): https://www.youtube.com/playlist?list=PL0NRmB0fnLJQAnYwkpt9PN2PBKx4rvdup Subscribe to Harvard CMSA seminar mailing list: https://forms.gle/1ewa7KeP6BxBuBeRA --- Harvard University CMSA, 20 Garden Street, Cambridge, MA 02138

6 months, 1 week

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Quantum Information Seminar by Matthias C. Caro

by Anshu, Anurag

Dear all, We are excited to have Matthias Caro from Freie Universität Berlin give a talk on Nov 2 (Thursday) from 4:30 pm - 5:30 pm in Jefferson 250. Details below and see you all there! Title: Classical Verification of Quantum Learning Abstract: Quantum data access and quantum processing can make certain classically intractable learning tasks feasible. However, quantum capabilities will only be available to a select few in the near future. Thus, reliable schemes that allow classical clients to delegate learning to untrusted quantum servers are required to facilitate widespread access to quantum learning advantages. Building on a recently introduced framework of interactive proof systems for classical machine learning, we develop a framework for classical verification of quantum learning. Based on a new quantum data access model that we call "mixture-of-superpositions" quantum examples, we exhibit learning problems that a classical learner cannot efficiently solve on their own, but that they can efficiently and reliably solve when interacting with an untrusted quantum prover. In contrast, we showcase two general scenarios in learning and verification in which quantum mixture-of-superpositions examples do not lead to sample complexity improvements over classical data. Our results demonstrate that the potential power of quantum data for learning tasks, while not unlimited, can be utilized by classical agents through interaction with untrusted quantum entities. With Best Regards, Anurag Anshu

6 months, 2 weeks

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[QMatter in Math/Physics 2023 Nov 3, Fri 10:00 - 11:30 am ET] Meng Cheng (Yale) Symmetry and many-body topology in mixed states - Harvard CMSA G10

by Juven Wang

Please circulate! Quantum Matter in Mathematics and Physics (QMMP) 2023: https://cmsa.fas.harvard.edu/event_category/quantum-matter-seminar/ ----- This seminar will be in person! *Time: Nov 3rd, Fri 10-11:30 am ET* *Location: Harvard CMSA G10* Zoom: https://harvard.zoom.us/j/977347126 Password: cmsa ————————————————————————————————— Meng Cheng (Yale) Title: Symmetry and many-body topology in mixed states Abstract: It is by now well-understood that gapped ground states of local Hamiltonians can be classified topologically, and the nontrivial states exhibit many interesting topological phenomena. In this talk I’ll discuss recent developments in generalizing the topological classification to mixed states. Global symmetry plays a key role in understanding phases in pure states. For mixed states, certain “weak” symmetries may hold “on average” for the entire ensemble, in contrast to “strong" symmetries respected by each state in the ensemble. I will show that the interplay between these two kinds of symmetries lead to a rich landscape of symmetry-protected mixed states, and can also be used to characterize mixed state topological order. -------- Subscribe to Harvard CMSA Quantum Matter and other seminar videos (more to be uploaded): https://www.youtube.com/playlist?list=PL0NRmB0fnLJQAnYwkpt9PN2PBKx4rvdup Subscribe to Harvard CMSA seminar mailing list: https://forms.gle/1ewa7KeP6BxBuBeRA

6 months, 2 weeks

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Internship opportunities at Lawrence Livermore Natl. Lab.

by Sule, Nishant V.

Dear all, I wanted to pass along information about some internship opportunities at Lawrence Livermore National Lab for graduate students. A representative from LLNL reached out to me specifically about the internships in the Physics Division where they are looking for students with a background in applied physics and condensed matter physics, and geared towards projects in quantum computing and sensing. Take a look at this job posting<https://www.llnl.gov/join-our-team/careers/find-your-job/internship/all/374…> of the internship. Note that this particular internship has no citizenship requirement. If any of you are interested, please feel free to apply and let me know, I’ll connect you to the individual who reached out. Best, Nishant

6 months, 2 weeks

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[Joint QMatter seminar 2023 Nov 2, Thu 4:30 pm - 6 pm ET] Liujun Zou (Perimeter) Landscape of quantum phases in quantum materials - Harvard CMSA G10

by Juven Wang

Please circulate --- Next seminar will be next Thursday (Nov 2). We skip our seminar this week to avoid the conflict with the ongoing important events: (1) Mathematics in Science: Perspectives and Prospects (10/27-10/28) (2) Kickoff Workshop for the Simons Collaboration on Celestial Holography (10/26-10/29). Joint Seminar of Quantum Matter in Mathematics and Physics (QMMP) and Topological Quantum Matter seminar: https://cmsa.fas.harvard.edu/event_category/quantum-matter-seminar/ https://cmsa.fas.harvard.edu/event_category/topological-quantum-matter-semi… ----- This seminar will be in person! *Time: Nov 2, Thu 4:30 pm - 6 pm ET* *Location: Harvard CMSA G10* Zoom: https://harvard.zoom.us/j/977347126 Password: cmsa ————————————————————————————————— Liujun Zou (Perimeter) Title: Landscape of quantum phases in quantum materials Abstract: A central goal of condensed matter physics is to understand which quantum phases of matter can emerge in a quantum material. For this purpose, one should be able to not only describe the quantum phases using some effective field theories, but also capture the important microscopic information of the material via mathematical formulation. In this talk, I will present a framework to classify quantum phases in quantum materials, where the microscopic information of a material is encoded in its quantum anomaly. I will talk about the application of this framework to classify various exotic quantum phases of matter in different lattice systems. Using our framework, we have obtained many results unexpected from the previous literature. -------- Subscribe to Harvard CMSA Quantum Matter and other seminar videos (more to be uploaded): https://www.youtube.com/playlist?list=PL0NRmB0fnLJQAnYwkpt9PN2PBKx4rvdup Subscribe to Harvard CMSA seminar mailing list: https://forms.gle/1ewa7KeP6BxBuBeRA --- Harvard University CMSA, 20 Garden Street, Cambridge, MA 02138

6 months, 2 weeks

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Wednesday, Nov. 1: HQI Special Seminar – Attosecond Quantum Optics

by Gallagher, Claire M.

HQI Special Seminar – Prof. Ido Kaminer Wednesday, Nov. 1 4:30 PM – 5:30 PM Jefferson 250 Ido Kaminer, Technion Title: "Attosecond Quantum Optics" The role of the quantum features of light in attosecond processes has remained unexplored. In a series of recent works, we developed the quantum-optical theory of attosecond processes and applied it to high harmonic generation (HHG). In this talk, I will show how the correlations between the emitters induce correlations between the emitted harmonics. Furthermore, I will show that the spectrum of HHG is sensitive to the photon statistics of the driving light. Thermal and squeezed light substantially increase the efficiency of HHG compared to a coherent light of the same intensity. The prospects of the attosecond quantum optics include the engineering of quantum many-photon states of light and creation of entangled attosecond pulses. Sincerely, Claire ___________ Claire M. Gallagher Staff Assistant III Harvard Quantum Initiative - MD 351

6 months, 2 weeks

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2024

2023

2022

Qse-grad-students November 2023