BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//CMSA - ECPv6.15.17//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:CMSA
X-ORIGINAL-URL:https://cmsa.fas.harvard.edu
X-WR-CALDESC:Events for CMSA
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-Robots-Tag:noindex
X-PUBLISHED-TTL:PT1H
BEGIN:VTIMEZONE
TZID:America/New_York
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20220313T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20221106T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20230312T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20231105T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20240310T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20241103T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20250309T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20251102T060000
END:STANDARD
END:VTIMEZONE
BEGIN:VTIMEZONE
TZID:America/New_York
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20220313T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20221106T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20230312T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20231105T060000
END:STANDARD
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:20240310T070000
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:20241103T060000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240223T100000
DTEND;TZID=America/New_York:20240223T113000
DTSTAMP:20260405T002142
CREATED:20240219T193919Z
LAST-MODIFIED:20240220T151759Z
UID:10001508-1708682400-1708687800@cmsa.fas.harvard.edu
SUMMARY:Spontaneously Broken (-1)-form symmetries
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Motoo Suzuki (Harvard) \nTitle: Spontaneously Broken (-1)-form symmetries \nAbstract: Spontaneous breaking of symmetries leads to universal phenomena. We extend this notion to (−1)-form U(1) symmetries. The spontaneous breaking is diagnosed by a dependence of the vacuum energy on a constant background field θ\, which can be probed by the topological susceptibility. This leads to a reinterpretation of the Strong CP problem as arising from a spontaneously broken instantonic symmetry in QCD. We discuss how known solutions to the problem are unified in this framework and explore some\, so far unsuccessful\, attempts to find new solutions. I will also talk about our ongoing work on the explicit breaking by monopoles.
URL:https://cmsa.fas.harvard.edu/event/qm-22824/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.23.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240216T103000
DTEND;TZID=America/New_York:20240216T120000
DTSTAMP:20260405T002142
CREATED:20240212T160753Z
LAST-MODIFIED:20240212T212952Z
UID:10001507-1708079400-1708084800@cmsa.fas.harvard.edu
SUMMARY:Programmable Simulations of Molecules and Materials with present-day Reconfigurable Quantum Processors
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Susanne Yelin (Harvard) \nTitle: Programmable Simulations of Molecules and Materials with present-day Reconfigurable Quantum Processors \nAbstract: Simulations of quantum chemistry and quantum materials are believed to be among the most important potential applications of quantum information processors\, but realizing practical quantum advantage for such problems is challenging. We introduce a simulation framework for strongly correlated quantum systems that can be represented by model spin Hamiltonians. Our approach leverages reconfigurable qubit architectures to programmably simulate real-time dynamics and introduces an algorithm for extracting chemically relevant spectral properties via classical co-processing of quantum measurement results. We develop a digital-analog simulation toolbox for efficient Hamiltonian time evolution utilizing digital Floquet engineering and hardware-optimized multi-qubit operations to accurately realize complex spin-spin interactions\, and as an example present an implementation proposal based on Rydberg atom arrays. Then\, we show how detailed spectral and other relevant chemical information can be extracted from these dynamics through snapshot measurements and single-ancilla control\, enabling the evaluation of excitation energies and finite-temperature susceptibilities from a single-dataset. To illustrate the approach\, we show how this method can be used to compute key properties of a polynuclear transition-metal catalyst and 2D magnetic materials.
URL:https://cmsa.fas.harvard.edu/event/qm-21624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.16.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240214T160000
DTEND;TZID=America/New_York:20240214T173000
DTSTAMP:20260405T002142
CREATED:20240212T162016Z
LAST-MODIFIED:20240212T211844Z
UID:10002103-1707926400-1707931800@cmsa.fas.harvard.edu
SUMMARY:Quantum Algebra of Chern-Simons Matrix Model and Large N Limit
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Sen Hu (Shanghai Institute for Mathematics and Interdisciplinary Study) \nTitle: Quantum Algebra of Chern-Simons Matrix Model and Large N Limit \nAbstract: In this talk we discuss the algebra of quantum observables of the Chern-Simons matrix model which was originally proposed by Susskind and Polychronakos to describe electrons in fractional quantum Hall effects. We establish the commutation relations for its generators and study the large N limit of its representation. We show that the large N limit algebra is isomorphic to the uniform in N algebra studied by Costello\, which is conjecturally isomorphic to the deformed double current algebra studied by Guay. Under appropriate scaling limit\, we show that the large N limit algebra degenerates to a Lie algebra which admits a surjective map to the affine Lie algebra of u(p). This leads to a complete proof of the large N emergence of the u(p) current algebra as proposed by Dorey\, Tong and Turner. This also suggests a rigorous derivation of edge excitation of a fractional quantum Hall droplet. This is a joint work with Si Li\, Dongheng Ye and Yehao Zhou (arXiv: 2308.14046).
URL:https://cmsa.fas.harvard.edu/event/qm-21424/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter,Seminars
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.14.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240209T093000
DTEND;TZID=America/New_York:20240209T110000
DTSTAMP:20260405T002142
CREATED:20240205T162614Z
LAST-MODIFIED:20240207T184606Z
UID:10001506-1707471000-1707476400@cmsa.fas.harvard.edu
SUMMARY:Quantum Algorithms to Recognize Phases of Matter and Exactly Solvable 2D Models with Anomalous Entanglement Entropy
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Soonwon Choi (MIT) \nTitle: Quantum Algorithms to Recognize Phases of Matter and  Exactly Solvable 2D Models with Anomalous Entanglement Entropy \nAbstract: In this talk\, I will report my two recent results at the intersection of quantum information and strongly interacting phases of matters. \nIn the first half of the talk\, we describe exact quantum algorithms that recognize a class of 1D gapped phases\, namely symmetry protected topological phases or spontaneous symmetry breaking phases protected by abelian internal symmetry. The key idea is to observe the conceptual similarity between renormalization group (RG) flow and error correction\, and to implement the latter as unitary circuits emulating the RG flow. Our algorithm guarantees faithful recognition of a target phase with a small number of input quantum state samples. \nIn the second half\, we present a class of 2D Hamiltonians\, where the exact ground state wavefunctions can be exactly evaluated and shown to exhibit anomalous entanglement properties. One class of our models exhibit area-law scaling entanglement entropy\, but this is mostly due to non-local correlation: one finds that the topological entanglement entropy also scales with the size of subsystem choices. By making simple modifications\, we can also devise 2D models with volume-law scaling bipartite entanglement entropy. Our results can be understood as a generation of the 1D Motzkin model to 2D systems. \nBased on work done with Ethan Lake and Shankar Balasubramanian \nhttps://arxiv.org/abs/2211.09803 \nhttps://arxiv.org/abs/2305.07028
URL:https://cmsa.fas.harvard.edu/event/qm-2924/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.09.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240206T160000
DTEND;TZID=America/New_York:20240206T173000
DTSTAMP:20260405T002142
CREATED:20240131T153258Z
LAST-MODIFIED:20240205T193624Z
UID:10001505-1707235200-1707240600@cmsa.fas.harvard.edu
SUMMARY:Flavor hierarchy from smooth confinement & Towards a complete classification of 6d supergravities
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Yuta Hamada (KEK\, Tsukuba) \nTitle: Flavor hierarchy from smooth confinement & Towards a complete classification of 6d supergravities \nAbstract: The talk consists of two independent parts. In the first part\, I will talk about a new model to explain the Standard Model flavor hierarchy. Our model is based on explicit smooth confinement. The smallness of the first- and second-family fermion masses is explained by the exponential hierarchy via dimensional transmutation. In the second part\, I will talk about a classification of 6D supergravities. We make progress towards a complete classification of 6D supergravities with minimal supersymmetry and non-abelian gauge group. \nReferences – arXiv: 2209.15244\, 2309.15152\, 2311.00868 \n 
URL:https://cmsa.fas.harvard.edu/event/qm_2624/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.06.2024.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240202T100000
DTEND;TZID=America/New_York:20240202T113000
DTSTAMP:20260405T002142
CREATED:20240129T153031Z
LAST-MODIFIED:20240130T205926Z
UID:10001318-1706868000-1706873400@cmsa.fas.harvard.edu
SUMMARY:Quantum Circuits to local Hamiltonian: role in quantum complexity and new constructions 
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Anurag Anshu (Harvard) \nTitle: Quantum Circuits to local Hamiltonian: role in quantum complexity and new constructions \nAbstract: At the heart of the theory of NP completeness lies a mapping from classical circuits to constraint satisfaction problems (classical local Hamiltonians). \nThe quantum analogue of this is the remarkable history state construction of Kitaev (building upon Feynman’s work). This talk will provide an introduction to this mapping and its crucial role in bridging quantum computer science and quantum many-body physics research. Then\, we will describe a new mapping using tensor networks and quantum fault tolerance (https://arxiv.org/abs/2309.16475). Time permitting\, we will discuss the relevance of this mapping to the quantum PCP conjecture.
URL:https://cmsa.fas.harvard.edu/event/qm_2224/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-02.02.24.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20240126T093000
DTEND;TZID=America/New_York:20240126T110000
DTSTAMP:20260405T002142
CREATED:20240118T143433Z
LAST-MODIFIED:20240118T192034Z
UID:10000860-1706261400-1706266800@cmsa.fas.harvard.edu
SUMMARY:Gauging spacetime inversions
DESCRIPTION:Quantum Matter in Mathematics and Physics Seminar \nSpeaker: Daniel Harlow (MIT) \nTitle: Gauging spacetime inversions \nAbstract: Spacetime inversion symmetries such as parity and time reversal play a central role in physics\, but they are usually treated as global symmetries. In quantum gravity there are no global symmetries\, so any spacetime inversion symmetries must be gauge symmetries. In particular this includes CRT symmetry (in even dimensions usually combined with a rotation to become CPT)\, which in quantum field theory is always a symmetry and seems likely to be a symmetry of quantum gravity as well. I’ll discuss what it means to gauge a spacetime inversion symmetry\, and explain some of the more unusual consequences of doing this. In particular I’ll argue that the gauging of CRT is automatically implemented by the sum over topologies in the Euclidean gravity path integral\, that in a closed universe the Hilbert space of quantum gravity must be a real vector space\, and that in Lorentzian signature manifolds which are not time-orientable must be included as valid configurations of the theory.
URL:https://cmsa.fas.harvard.edu/event/qm-2/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-01.26.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231215T100000
DTEND;TZID=America/New_York:20231215T113000
DTSTAMP:20260405T002142
CREATED:20240222T093357Z
LAST-MODIFIED:20240222T093357Z
UID:10002796-1702634400-1702639800@cmsa.fas.harvard.edu
SUMMARY:Exact lattice chiral symmetry in 2d gauge theory
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Aleksey Cherman (UMN) \nTitle: Exact lattice chiral symmetry in 2d gauge theory \nAbstract: Preserving the symmetries of massless fermions is a well-known challenge in lattice field theory.  I’ll discuss symmetry-preserving lattice regularizations of 2d QED with one and two flavors of Dirac fermions\, as well as the `3450′ chiral gauge theory. The construction leverages bosonization and recently-proposed modifications of Villain-type lattice actions. The internal global symmetries act just as locally on the lattice as they do in the continuum\, the anomalies are reproduced at finite lattice spacing\, and in each case we’ve found a sign-problem-free dual formulation.
URL:https://cmsa.fas.harvard.edu/event/qm_121523/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-12.15.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231214T143000
DTEND;TZID=America/New_York:20231214T160000
DTSTAMP:20260405T002142
CREATED:20240109T001602Z
LAST-MODIFIED:20240109T001934Z
UID:10001133-1702564200-1702569600@cmsa.fas.harvard.edu
SUMMARY:When does a three-dimensions Chern-Simons theory have a time reversal symmetry?
DESCRIPTION:Speaker: Roman Geiko (UCLA) \nTitle: When does a three-dimensions Chern-Simons theory have a time reversal symmetry? \nIn this talk\, I will discuss the time reversal invariance of (spin-) Chern-Simons theory in 3 dimensions at both classical and quantum levels. I will show how to obtain a complete classification of Abelian anyons with the time reversal symmetry expressed in terms of the higher Gauss sums. Then\, I will comment on the time reversal symmetry of Chern-Simons in the non-Abelian case.
URL:https://cmsa.fas.harvard.edu/event/qm_121423/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-12.14.2023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231208T143000
DTEND;TZID=America/New_York:20231208T160000
DTSTAMP:20260405T002142
CREATED:20240221T100009Z
LAST-MODIFIED:20240221T100109Z
UID:10002772-1702045800-1702051200@cmsa.fas.harvard.edu
SUMMARY:Fermi surface symmetric mass generation and its application in nickelate superconductor
DESCRIPTION:Joint Quantum Matter in Mathematics and Physics & Topological Quantum Matter Seminar \nSpeaker: Da-Chuan Lu (UCSD) \nTitle: Fermi surface symmetric mass generation and its application in nickelate superconductor \nAbstract: Symmetric mass generation (SMG) is a novel interaction-driven mechanism that generates fermion mass without breaking symmetry\, unlike the standard Anderson-Higgs mechanism. SMG can occur in the fermion system without quantum anomalies. In this talk\, I will focus on the SMG for the systems with finite fermion density\, i.e.\, the Fermi surface. I will discuss the Fermi surface anomaly and Fermi surface SMG. Lastly\, I will talk about its application in the newly found nickelate superconductors\, where the superconductivity emerges without a nearby spontaneous symmetry-breaking phase.
URL:https://cmsa.fas.harvard.edu/event/qm_12823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Quantum-Matter_String-Seminar-12.08.2023.docx-2.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231201T163000
DTEND;TZID=America/New_York:20231201T173000
DTSTAMP:20260405T002142
CREATED:20230802T170029Z
LAST-MODIFIED:20240813T162053Z
UID:10001173-1701448200-1701451800@cmsa.fas.harvard.edu
SUMMARY:A Plane Defect in the 3d O(N) Model
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Abijith Krishnan (MIT) \nTitle: A Plane Defect in the 3d O(N) Model \nAbstract: It was recently found that the classical 3d O(N) model in the semi-infinite geometry can exhibit an “extraordinary-log” boundary universality class\, where the spin-spin correlation function on the boundary falls off as (log x)^(-q). This universality class exists for a range 2≤N<Nc and Monte-Carlo simulations and conformal bootstrap indicate Nc>3. In this talk\, I’ll extend this result to the 3d O(N) model in an infinite geometry with a plane defect. I’ll explain using the renormalization group (RG) that the extraordinary-log universality class is present for any finite N≥2\, and that a line of defect fixed points is present at N=∞. This line of defect fixed points is lifted to the ordinary\, special (no defect) and extraordinary-log universality classes by 1/N corrections. I’ll show that the line of defect fixed points and the 1/N corrections agree with an a-theorem by Jensen and O’Bannon for 3d CFTs with a boundary. Finally\, I’ll conclude by noting some physical systems where the extraordinary-log universality class can be observed. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_33123/
LOCATION:Hybrid
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-Topological-Seminar-12.01.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231122T160000
DTEND;TZID=America/New_York:20231122T173000
DTSTAMP:20260405T002142
CREATED:20240221T102006Z
LAST-MODIFIED:20240221T102032Z
UID:10002775-1700668800-1700674200@cmsa.fas.harvard.edu
SUMMARY:Modulated Gauge Theories and Fracton Behavior in 2D
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Guilherme Delfino Silva (Boston University) \nTitle: Modulated Gauge Theories and Fracton Behavior in 2D \nAbstract: In this talk we investigate deconfined phases of two-dimensional ZN lattice gauge theories associated to spatially modulated symmetries. In order to study the low-energy physics of such modulated gauge theories we propose and explore exactly solvable gapped Hamiltonians\, which allow us to fully characterize their low-energy properties at zero temperature. We provide explicit examples and discuss how non-polynomial symmetries\, as exponential symmetries\, are powerful enough to fully constrain the mobility of isolated excitations.
URL:https://cmsa.fas.harvard.edu/event/qm_112223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-11.22.2023..png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231107T163000
DTEND;TZID=America/New_York:20231107T180000
DTSTAMP:20260405T002142
CREATED:20240222T091622Z
LAST-MODIFIED:20240222T091622Z
UID:10002794-1699374600-1699380000@cmsa.fas.harvard.edu
SUMMARY: A Long Exact Sequence in Symmetry Breaking
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Cameron Krulewski (MIT) and Leon Liu (Harvard) \nTitle: A Long Exact Sequence in Symmetry Breaking \nAbstract: 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). \nThe 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 \nspectra 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.
URL:https://cmsa.fas.harvard.edu/event/qm_11723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-11.07.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20231011T163000
DTEND;TZID=America/New_York:20231011T180000
DTSTAMP:20260405T002142
CREATED:20240222T060902Z
LAST-MODIFIED:20240222T060902Z
UID:10002785-1697041800-1697047200@cmsa.fas.harvard.edu
SUMMARY:Non-invertible symmetries\, leptons\, quarks\, and why multiple generations
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Seth Koren (Notre Dame) \nTitle: Non-invertible symmetries\, leptons\, quarks\, and why multiple generations \nAbstract: Generalized global symmetries are present in theories of particle physics\, and understanding their structure can give insight into these theories and UV completions thereof.  After discussing the generalized symmetries of the Standard Model\, we will go Beyond and show that the identification of a non-invertible symmetry of Z’ models of L_µ – L_τ reveals the existence of non-Abelian horizontal gauge theories which naturally produce exponentially small Dirac neutrino masses. Next we will uncover a subtler non-invertible symmetry in horizontal gauge theories of the quark sector which will lead us to a massless down-type quarks solution to strong CP in color-flavor unification. Intriguingly\, this theory works by virtue of the SM having the same numbers of colors and generations.
URL:https://cmsa.fas.harvard.edu/event/qm_101123/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-10.11.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230928T163000
DTEND;TZID=America/New_York:20230928T180000
DTSTAMP:20260405T002142
CREATED:20240221T112307Z
LAST-MODIFIED:20240813T161833Z
UID:10002780-1695918600-1695924000@cmsa.fas.harvard.edu
SUMMARY:Quantum field theory approach to quantum information
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Cenke Xu (UCSB) \nTitle: Quantum field theory approach to quantum information \nAbstract: We apply the formalism of quantum field theory and Euclidean space-time path integral to investigate a class of quantum information problems. In particular\, we investigate quantum many-body systems under weak-measurement and decoherence. The Euclidean space-time path integral allows us to map this problem to a quantum field theory with (temporal) boundary or defects. We therefore investigate two types of quantum many-body systems with nontrivial boundary physics: quantum critical points\, and states with nontrivial topology\, such as Chern insulator and symmetry protected topological states. For example\, we demonstrate that a Wilson-Fisher quantum critical point can be driven into an “extraordinary-log” phase after weak-measurement. Another example is that\, we argue that a system with higher form symmetry may be driven to a self-dual phase transition under weak measurement.
URL:https://cmsa.fas.harvard.edu/event/qm_92823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.28.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230922T100000
DTEND;TZID=America/New_York:20230922T113000
DTSTAMP:20260405T002142
CREATED:20240223T095601Z
LAST-MODIFIED:20240223T095601Z
UID:10002845-1695376800-1695382200@cmsa.fas.harvard.edu
SUMMARY:Floquet codes\, automorphisms\, and quantum computation
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Margarita Davydova (MIT) \nTitle: Floquet codes\, automorphisms\, and quantum computation \nAbstract: In this talk\, I will introduce a new kind of measurement-based quantum computation inspired by Floquet codes. In this model\, the quantum logical gates are implemented by short sequences of low-weight measurements which simultaneously encode logical information and enable error correction.  We introduce a new class of quantum error-correcting codes generalizing Floquet codes that achieve this\, which we call dynamic automorphism (DA) codes. \nAs in Floquet codes\, the instantaneous codespace of a DA code at any fixed point in time is that of a topological code. In this case\, the quantum computation can be viewed as a sequence of time-like domain walls implementing automorphisms of the topological order\, which can be understood in terms of reversible anyon condensation paths in a particular parent model.  This talk will introduce all of these concepts as well as provide a new perspective for thinking about Floquet codes. \nThe explicit examples that we construct\, which we call DA color codes\, can implement the full Clifford group of logical gates in 2+1d by two- and\, rarely three-body measurements. Using adaptive two-body measurements\, we can achieve a non-Clifford gate in 3+1d\, making the first step towards universal quantum computation in this model. \nThe talk is based on recent work with Nathanan Tantivasadakarn\, Shankar Balasubramanian\, and David Aasen [arxiv: 2307.10353].
URL:https://cmsa.fas.harvard.edu/event/qm_92223/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.22.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230913T163000
DTEND;TZID=America/New_York:20230913T180000
DTSTAMP:20260405T002142
CREATED:20240223T111403Z
LAST-MODIFIED:20240223T111403Z
UID:10002859-1694622600-1694628000@cmsa.fas.harvard.edu
SUMMARY:Anomalies of Non-Invertible Symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Clay Córdova (U Chicago) \nTitle: Anomalies of Non-Invertible Symmetries
URL:https://cmsa.fas.harvard.edu/event/qm_91323/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230908T100000
DTEND;TZID=America/New_York:20230908T113000
DTSTAMP:20260405T002142
CREATED:20230904T055802Z
LAST-MODIFIED:20240116T070515Z
UID:10001125-1694167200-1694172600@cmsa.fas.harvard.edu
SUMMARY:A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Xiao-Gang Wen (MIT) \nTitle: A 6-year journey: from gravitational anomaly to a unified theory of generalized symmetry \nAbstract: Emergent symmetry can be generalized symmetry beyond (higher) group description and/or can be anomalous. I will describe a unified theory for generalized symmetry based on symmetry/topological-order correspondence. I will also discuss some applications of emergent generalized symmetry.
URL:https://cmsa.fas.harvard.edu/event/qm_9823/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-09.08.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230824T100000
DTEND;TZID=America/New_York:20230824T113000
DTSTAMP:20260405T002142
CREATED:20230904T055455Z
LAST-MODIFIED:20240227T085359Z
UID:10001126-1692871200-1692876600@cmsa.fas.harvard.edu
SUMMARY:Two of my favorite numbers: 8 and 24
DESCRIPTION:Quantum Matter Seminar \nSpeaker: John Baez (University of California\, Riverside) \nTitle: Two of my favorite numbers: 8 and 24 \nAbstract: The numbers 8 and 24 play special roles in mathematics. The number 8 is special because of Bott periodicity\, the octonions and the E8 lattice\, while 24 is special for many reasons\, including the binary tetrahedral group\, the 3rd stable homotopy group of spheres\, and the Leech lattice. The number 8 does for superstring theory what the number 24 does for bosonic string theory. In this talk\, which is intended to be entertaining\, I will overview these matters and also some connections between the numbers 8 and 24.
URL:https://cmsa.fas.harvard.edu/event/qm_82423/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-08.24.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230630T100000
DTEND;TZID=America/New_York:20230630T113000
DTSTAMP:20260405T002142
CREATED:20230802T171855Z
LAST-MODIFIED:20240110T074010Z
UID:10001183-1688119200-1688124600@cmsa.fas.harvard.edu
SUMMARY:Monopoles\, Scattering\, and Generalized Symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Marieke Van Beest (SCGP) \nTitle: Monopoles\, Scattering\, and Generalized Symmetries \nAbstract: In this talk\, we will discuss the problem of electrically charged\, massless fermions scattering off magnetic monopoles. The interpretation of the outgoing states has long been a puzzle\, as they can carry fractional quantum numbers. We argue that such outgoing particles live in the twisted sector of a topological co-dimension 1 surface\, which ends topologically on the monopole. This symmetry defect is often non-invertible\, and as such the outgoing radiation not only carries unconventional flavor quantum numbers\, but is often trailed by a topological field theory\, which is a new prediction.
URL:https://cmsa.fas.harvard.edu/event/qm_63023/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-06.30.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230626T100000
DTEND;TZID=America/New_York:20230626T113000
DTSTAMP:20260405T002142
CREATED:20230802T171648Z
LAST-MODIFIED:20240110T073717Z
UID:10001182-1687773600-1687779000@cmsa.fas.harvard.edu
SUMMARY:Chiral fermionic CFTs of central charge ≤ 16
DESCRIPTION:Quantum Matter Seminar \nTitle: Chiral fermionic CFTs of central charge ≤ 16 \nAbstract: We classified all chiral fermionic CFTs of central charge ≤ 16 using Kac’s theorem and bosonization/fermionization. This talk will discuss the derivation of this result\, its application to the classification of non-supersymmetric heterotic string theories\, and along the way we’ll address some oft-overlooked subtleties of bosonization from the point of view of anomalies and topological phases.
URL:https://cmsa.fas.harvard.edu/event/qm_62623/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-06.26.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230613T100000
DTEND;TZID=America/New_York:20230613T120000
DTSTAMP:20260405T002142
CREATED:20230802T171505Z
LAST-MODIFIED:20240228T070233Z
UID:10001181-1686650400-1686657600@cmsa.fas.harvard.edu
SUMMARY:Small Bosonic CFTs\, Chiral Fermionization\, and Symmetry/Subalgebra Duality
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Brandon C. Rayhaun (C. N. Yang ITP\, Stony Brook University) \nTitle: Small Bosonic CFTs\, Chiral Fermionization\, and Symmetry/Subalgebra Duality \nAbstract: Conformal field theories in (1+1)D are key actors in many dramas of physics and mathematics. Their classification has therefore been an important and long-standing problem. In this talk\, I will explain the main ideas behind the classification of (most) “small” bosonic CFTs. Here\, I use the adjective “small” informally to refer to theories with low central charge (less than 24) and few primary operators (less than 5). Time and attention permitting\, I will highlight two applications of this result. First\, I will describe how it can be used in tandem with bosonization and fermionization techniques to establish the classification of chiral fermionic CFTs with central charge less than 23. Second\, I will showcase how it can be used to bootstrap generalized global symmetries using the concept of “symmetry/subalgebra duality.” \nTalk based on arXiv:2208.05486 [hep-th] (joint work with Sunil Mukhi) and arXiv:2303.16921 [hep-th]. \n \n 
URL:https://cmsa.fas.harvard.edu/event/qm_61323/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-06.13.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230609T100000
DTEND;TZID=America/New_York:20230609T113000
DTSTAMP:20260405T002142
CREATED:20230802T171314Z
LAST-MODIFIED:20240215T111159Z
UID:10001180-1686304800-1686310200@cmsa.fas.harvard.edu
SUMMARY:Classification of Self-Dual Vertex Operator Superalgebras of Central Charge at Most 24
DESCRIPTION:Quantum Matter Seminar \nSpeakers: Gerald Höhn (Kansas State University) & Sven Möller (University of Hamburg) \nTitle: Classification of Self-Dual Vertex Operator Superalgebras of Central Charge at Most 24 \nAbstract: We discuss the classfication of self-dual vertex operator superalgebras (SVOAs) of central charge 24\, or in physics parlance the purely chiral 2-dimensional fermionic conformal field theories with just one primary field. \nThere are exactly 969 such SVOAs under suitable regularity assumptions and the assumption that the shorter moonshine module VB^# is the unique self-dual SVOA of central charge 23.5 whose weight-1/2 and weight-1 spaces vanish. \nWe construct and classify the self-dual SVOAs by determining the 2-neighbourhood graph of the self-dual (purely bosonic) VOAs of central charge 24 and also by realising them as simple-current extensions of a dual pair containing a certain maximal lattice VOA. We show that all SVOAs besides VB^# x F and potential fake copies thereof stem from elements of the Conway group Co_0\, the automorphism group of the Leech lattice. \nBy splitting off free fermions F\, if possible\, we obtain the classification for all central charges less than or equal to 24.\nReference: G. Höhn\, S. Möller\, arXiv:2303.17190.
URL:https://cmsa.fas.harvard.edu/event/qm_6923/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-06.09.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230512T100000
DTEND;TZID=America/New_York:20230512T113000
DTSTAMP:20260405T002142
CREATED:20230802T171128Z
LAST-MODIFIED:20240215T111609Z
UID:10001179-1683885600-1683891000@cmsa.fas.harvard.edu
SUMMARY:Anomalies of (1+1)D categorical symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Carolyn Zhang (U Chicago) \nTitle: Anomalies of (1+1)D categorical symmetries \nAbstract: We present a general approach for detecting when a fusion category symmetry is anomalous\, based on the existence of a special kind of Lagrangian algebra of the corresponding Drinfeld center. The Drinfeld center of a fusion category $A$ describes a $(2+1)D$ topological order whose gapped boundaries enumerate all $(1+1)D$ gapped phases with the fusion category symmetry\, which may be spontaneously broken. There always exists a gapped boundary\, given by the \emph{electric} Lagrangian algebra\, that describes a phase with $A$ fully spontaneously broken. The symmetry defects of this boundary can be identified with the objects in $A$. We observe that if there exists a different gapped boundary\, given by a \emph{magnetic} Lagrangian algebra\, then there exists a gapped phase where $A$ is not spontaneously broken at all\, which means that $A$ is not anomalous. In certain cases\, we show that requiring the existence of such a magnetic Lagrangian algebra leads to highly computable obstructions to $A$ being anomaly-free. As an application\, we consider the Drinfeld centers of $\mathbb{Z}_N\times\mathbb{Z}_N$ Tambara-Yamagami fusion categories and recover known results from the study of fiber functors.
URL:https://cmsa.fas.harvard.edu/event/qm_51223/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-05.12.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230505T100000
DTEND;TZID=America/New_York:20230505T113000
DTSTAMP:20260405T002142
CREATED:20230802T170945Z
LAST-MODIFIED:20240110T072755Z
UID:10001178-1683280800-1683286200@cmsa.fas.harvard.edu
SUMMARY:Detecting central charge in a superconducting quantum processor
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Sona Najafi (IBM Quantum) \nTitle: Detecting central charge in a superconducting quantum processor \nAbstract: Physical systems at the continuous phase transition point exhibit conformal symmetry rendering local scaling invariance. In two dimensions\, the conformal group possesses infinite generators described by Virasoro algebra with an essential parameter known as a central charge. While the central charge manifests itself in a variety of quantities\, its detection in experimental setup remains elusive. In this work\, we utilize Shannon-Renyi entropy on a local basis of a one-dimensional quantum spin chain at a critical point. We first use a simulated variational quantum eigen solver to prepare the ground state of the critical transfer field Ising model and XXZ model with open and periodic boundary conditions and perform local Pauli X and Z basis measurements. Using error mitigation such as probabilistic error cancellation\, we extract an estimation of the local Pauli observables needed to determine the Shannon-Renyi entropy with respect to subsystem size. Finally\, we obtain the central charge in the sub-leading term of Shannon-Renyi entropy.
URL:https://cmsa.fas.harvard.edu/event/qm_5523/
LOCATION:Hybrid – G10
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-05.05.23-2.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230428T100000
DTEND;TZID=America/New_York:20230428T113000
DTSTAMP:20260405T002142
CREATED:20230802T170750Z
LAST-MODIFIED:20240215T115157Z
UID:10001177-1682676000-1682681400@cmsa.fas.harvard.edu
SUMMARY:Fracton Self-Statistics
DESCRIPTION:Quantum Matter Seminar \nTitle: Fracton Self-Statistics \nSpeaker: Hao Song (ITP-CAS) \nAbstract: Fracton order describes novel quantum phases of matter that host quasiparticles with restricted mobility\, and thus lies beyond the existing paradigm of topological order. In particular\, excitations that cannot move without creating other excitations are called fractons. Here we address a fundamental open question — can the notion of self-exchange statistics be naturally defined for fractons\, given their complete immobility as isolated excitations? Surprisingly\, we demonstrate how fractons can be exchanged\, and show their self-statistics is a key part of the characterization of fracton orders. We derive general constraints satisfied by the fracton self-statistics in a large class of abelian fracton orders. Finally\, we show the existence of semionic or fermionic fracton self-statistics in some twisted variants of the checkerboard model and Haah’s code\, establishing that these models are in distinct quantum phases as compared to their untwisted cousins. \nReferences: H Song\, N Tantivasadakarn\, W Shirley\, M Hermele\, arXiv:2304.00028.
URL:https://cmsa.fas.harvard.edu/event/qm_42823/
LOCATION:Virtual
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.28.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230421T100000
DTEND;TZID=America/New_York:20230421T113000
DTSTAMP:20260405T002142
CREATED:20230802T170556Z
LAST-MODIFIED:20240131T001826Z
UID:10001176-1682071200-1682076600@cmsa.fas.harvard.edu
SUMMARY:A model of the cuprates: from the pseudogap metal to d-wave superconductivity and charge order
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Prof. Subir Sachdev (Harvard) \nTitle: A model of the cuprates: from the pseudogap metal to d-wave superconductivity and charge order \nAbstract: Soon after the discovery of high-temperature superconductivity in the cuprates\, Anderson proposed a connection to quantum spin liquids. But observations since then have shown that the low-temperature phase diagram is dominated by conventional states\, with a competition between superconductivity and charge-ordered states which break translational symmetry. We employ the “pseudogap metal” phase\, found at intermediate temperatures and low hole doping\, as the parent to the phases found at lower temperatures. The pseudogap metal is described as a fractionalized phase of a single-band model\, with small pocket Fermi surfaces of electron-like quasiparticles whose enclosed area is not equal to the free electron value\, and an underlying pi-flux spin liquid with an emergent SU(2) gauge field. This pi-flux spin liquid is now known to be unstable to confinement at sufficiently low energies. We develop a theory of the different routes to confinement of the pi-flux spin liquid and show that d-wave superconductivity\, antiferromagnetism\, and charge order are natural outcomes. We argue that this theory provides routes to resolving a number of open puzzles on the cuprate phase diagram.\nAs a side result\, at half-filling\, we propose a deconfined quantum critical point between an antiferromagnet and a d-wave superconductor described by a conformal gauge theory of 2 flavors of massless Dirac fermions and 2 flavors of complex scalars coupled as fundamentals to a SU(2) gauge field.\nThis talk is based on Maine Christos\, Zhu-Xi Luo\, Henry Shackleton\, Mathias S. Scheurer\, and S. S.\, arXiv:2302.07885
URL:https://cmsa.fas.harvard.edu/event/qm_42123/
LOCATION:Hybrid – G10
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.21.23-1.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230414T100000
DTEND;TZID=America/New_York:20230414T113000
DTSTAMP:20260405T002142
CREATED:20230802T170408Z
LAST-MODIFIED:20240110T072019Z
UID:10001175-1681466400-1681471800@cmsa.fas.harvard.edu
SUMMARY:Fault-tolerant quantum computation via topological order on fractals and emergent symmetries
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Guanyu Zhu (IBM Quantum\, T. J. Watson Research Center) \nTitle: Fault-tolerant quantum computation via topological order on fractals and emergent symmetries \nAbstract: Topological quantum error correcting codes in integer spatial dimensions have been widely studied in the field of quantum information. A remaining major challenge is to reduce the space-time overhead for universal fault-tolerant quantum computation with topological codes. In the first part of my talk\, I will present a theory of topological order and quantum codes on fractals embedded in three and higher dimensions and its connection to systolic geometry. The construction of such fractal codes can hence significantly reduce the space overhead. In the second part\, I will show how to perform fault-tolerant non-Clifford logical gates in such fractal codes using the idea of emergent symmetries. In particular\, I will discuss the existence of higher-form symmetries corresponding to sweeping of certain codimension-2 invertible defects and exotic gapped boundaries which condense such defects. \nReferences:\n1. PRX Quantum 3 (3)\, 030338 (2022)\, Guanyu Zhu\, Tomas Jochym-O’Connor\, Arpit Dua\n2. arXiv:2201.03568 (2022)\, Arpit Dua\, Tomas Jochym-O&#39;Connor\, Guanyu Zhu\n3. arXiv:2208.07367 (2022)\, Maissam Barkeshli\, Yu-An Chen\, Sheng-Jie Huang\, Ryohei Kobayashi\, Nathanan Tantivasadakarn\, Guanyu Zhu \n 
URL:https://cmsa.fas.harvard.edu/event/qm_4142023/
LOCATION:Hybrid – G10
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.14.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230407T100000
DTEND;TZID=America/New_York:20230407T113000
DTSTAMP:20260405T002142
CREATED:20230802T170222Z
LAST-MODIFIED:20240110T071718Z
UID:10001174-1680861600-1680867000@cmsa.fas.harvard.edu
SUMMARY:Enhancing Detection of Topological Order by Local Error Correction
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Nishad Maskara (Harvard) \nTitle: Enhancing Detection of Topological Order by Local Error Correction \nAbstract: The exploration of topologically-ordered states of matter is a long-standing goal at the interface of several subfields of the physical sciences. Such states feature intriguing physical properties such as long-range entanglement\, emergent gauge fields and non-local correlations\, and can aid in realization of scalable fault-tolerant quantum computation. However\, these same features also make creation\, detection\, and characterization of topologically-ordered states particularly challenging. Motivated by recent experimental demonstrations\, we introduce a new paradigm for quantifying topological states—locally error-corrected decoration (LED)—by combining methods of error correction with ideas of renormalization-group flow. Our approach allows for efficient and robust identification of topological order\, and is applicable in the presence of incoherent noise sources\, making it particularly suitable for realistic experiments. We demonstrate the power of LED using numerical simulations of the toric code under a variety of perturbations\, and we subsequently apply it to an experimental realization of a quantum spin liquid using a Rydberg-atom quantum simulator.  Finally\, we illustrate how LED can be applied to more general phases including non-abelian topological orders. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_4723/
LOCATION:CMSA Room G10\, CMSA\, 20 Garden Street\, Cambridge\, MA\, 02138\, United States
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-04.07.23.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/New_York:20230324T100000
DTEND;TZID=America/New_York:20230324T113000
DTSTAMP:20260405T002142
CREATED:20230802T165633Z
LAST-MODIFIED:20240110T055248Z
UID:10001172-1679652000-1679657400@cmsa.fas.harvard.edu
SUMMARY:Traversable wormhole dynamics on a quantum processor
DESCRIPTION:Quantum Matter Seminar \nSpeaker: Alexander Zlokapa\, MIT \nTitle: Traversable wormhole dynamics on a quantum processor \nAbstract: The holographic principle\, theorized to be a property of quantum gravity\, postulates that the description of a volume of space can be encoded on a lower-dimensional boundary. The anti-de Sitter (AdS)/conformal field theory correspondence or duality is the principal example of holography. The Sachdev–Ye–Kitaev (SYK) model of N >> 1 Majorana fermions has features suggesting the existence of a gravitational dual in AdS2\, and is a new realization of holography. We invoke the holographic correspondence of the SYK many-body system and gravity to probe the conjectured ER=EPR relation between entanglement and spacetime geometry through the traversable wormhole mechanism as implemented in the SYK model. A qubit can be used to probe the SYK traversable wormhole dynamics through the corresponding teleportation protocol. This can be realized as a quantum circuit\, equivalent to the gravitational picture in the semiclassical limit of an infinite number of qubits. Here we use learning techniques to construct a sparsified SYK model that we experimentally realize with 164 two-qubit gates on a nine-qubit circuit and observe the corresponding traversable wormhole dynamics. Despite its approximate nature\, the sparsified SYK model preserves key properties of the traversable wormhole physics: perfect size winding\, coupling on either side of the wormhole that is consistent with a negative energy shockwave\, a Shapiro time delay\, causal time-order of signals emerging from the wormhole\, and scrambling and thermalization dynamics. Our experiment was run on the Google Sycamore processor. By interrogating a two-dimensional gravity dual system\, our work represents a step towards a program for studying quantum gravity in the laboratory. Future developments will require improved hardware scalability and performance as well as theoretical developments including higher-dimensional quantum gravity duals and other SYK-like models. \n 
URL:https://cmsa.fas.harvard.edu/event/qm_32423/
LOCATION:Hybrid – G10
CATEGORIES:Quantum Matter
ATTACH;FMTTYPE=image/png:https://cmsa.fas.harvard.edu/media/CMSA-QMMP-03.24.23.png
END:VEVENT
END:VCALENDAR