
Speaker: Aleksey ChermanTitle: Exact lattice chiral symmetry in 2d gauge theoryVenue: virtualQuantum Matter Seminar Speaker: Aleksey Cherman (UMN) Title: Exact lattice chiral symmetry in 2d gauge theory Abstract: Preserving the symmetries of massless fermions is a wellknown challenge in lattice field theory. I’ll discuss symmetrypreserving 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 recentlyproposed modifications of Villaintype 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 signproblemfree dual formulation. 

Speaker: Cameron Krulewski (MIT) and Leon Liu (Harvard)Title: A Long Exact Sequence in Symmetry BreakingVenue: CMSA Room G10Quantum Matter Seminar 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 anomalymatching 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… 

Speaker: Meng ChengTitle: Symmetry and manybody topology in mixed statesVenue: CMSA Room G10Quantum Matter Seminar Speaker: Meng Cheng (Yale) Title: Symmetry and manybody topology in mixed states Abstract: It is by now wellunderstood 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 symmetryprotected mixed states, and can also be used… 

Speaker: Liujun ZouTitle: Landscape of quantum phases in quantum materialsVenue: CMSA Room G10Joint Quantum Matter in Mathematics and Physics and Topological Quantum Matter Seminar Speaker: Liujun Zou (Perimeter Institute) 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… 

Speaker: Cheryne JonayTitle: A Physical Theory of Twostage ThermalizationVenue: CMSA Room G10Quantum Matter Seminar Speaker: Cheryne Jonay (Stanford) Title: A Physical Theory of Twostage Thermalization Abstract: One indication of thermalization time is subsystem entanglement reaching thermal values. Recent studies on local quantum circuits reveal two exponential stages with decay rates $r_1$ and $r_2$ of the purity before and after thermalization. We provide an entanglement membrane theory interpretation, with $r_1$ corresponding to the domain wall free energy. Circuit geometry can lead to $r_1 < r_2$, producing a “phantom eigenvalue”. Competition between the domain wall and magnon leads to $r_2 < r_1$ when the magnon prevails. However, when the domain wall wins, this mechanism provides a practical approach for measuring entanglement growth through local correlation functions. 

Speaker: Seth KorenTitle: Noninvertible symmetries, leptons, quarks, and why multiple generationsVenue: CMSA Room G10Quantum Matter Seminar Speaker: Seth Koren (Notre Dame) Title: Noninvertible symmetries, leptons, quarks, and why multiple generations Abstract: 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 noninvertible symmetry of Z’ models of L_µ – L_τ reveals the existence of nonAbelian horizontal gauge theories which naturally produce exponentially small Dirac neutrino masses. Next we will uncover a subtler noninvertible symmetry in horizontal gauge theories of the quark sector which will lead us to a massless downtype quarks solution to strong CP in colorflavor unification. Intriguingly,… 

Speaker: Nat TantivasadakarnTitle: From wavefunction collapse and Galois solvability to the realization of nonAbelian topological order on a quantum deviceVenue: CMSA Room G10Quantum Matter Seminar Speaker: Nat Tantivasadakarn (Caltech) Title: From wavefunction collapse and Galois solvability to the realization of nonAbelian topological order on a quantum device Abstract: I will review our recent set of theoretical works on efficiently preparing long range quantum entanglement with adaptive quantum circuits: the combination of measurements with unitary gates whose choice can depend on previous measurement outcomes. I will show that this additional ingredient can be leveraged to prepare the long soughtafter nonAbelian topological phases with a circuit depth that is independent of system size. Using this framework, we uncover a complexity hierarchy of longrange entangled states based on the minimal number of measurement layers required to create the state. Moreover, we find that… 

Speaker: Cenke XuTitle: Quantum field theory approach to quantum informationVenue: CMSA Room G10Quantum Matter Seminar Speaker: Cenke Xu (UCSB) Title: Quantum field theory approach to quantum information Abstract: We apply the formalism of quantum field theory and Euclidean spacetime path integral to investigate a class of quantum information problems. In particular, we investigate quantum manybody systems under weakmeasurement and decoherence. The Euclidean spacetime 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 manybody 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 WilsonFisher quantum critical point can be driven into an “extraordinarylog” phase after weakmeasurement…. 

Speaker: Margarita DavydovaTitle: Floquet codes, automorphisms, and quantum computationVenue: CMSA Room G10Quantum Matter Seminar Speaker: Margarita Davydova (MIT) Title: Floquet codes, automorphisms, and quantum computation Abstract: In this talk, I will introduce a new kind of measurementbased quantum computation inspired by Floquet codes. In this model, the quantum logical gates are implemented by short sequences of lowweight measurements which simultaneously encode logical information and enable error correction. We introduce a new class of quantum errorcorrecting codes generalizing Floquet codes that achieve this, which we call dynamic automorphism (DA) codes. As 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 timelike domain walls implementing automorphisms of the topological order,… 

Speaker: Clay CórdovaTitle: Anomalies of NonInvertible SymmetriesVenue: CMSA Room G10Quantum Matter Seminar Speaker: Clay Córdova (U Chicago) Title: Anomalies of NonInvertible Symmetries 

Speaker: XiaoGang WenTitle: A 6year journey: from gravitational anomaly to a unified theory of generalized symmetryVenue: CMSA Room G10Quantum Matter Seminar Speaker: XiaoGang Wen (MIT) Title: A 6year journey: from gravitational anomaly to a unified theory of generalized symmetry Abstract: 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/topologicalorder correspondence. I will also discuss some applications of emergent generalized symmetry. 

Speaker: John BaezTitle: Two of my favorite numbers: 8 and 24Venue: virtualQuantum Matter Seminar Speaker: John Baez (University of California, Riverside) Title: Two of my favorite numbers: 8 and 24 Abstract: 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. 

Speaker: Marieke Van BeestTitle: Monopoles, Scattering, and Generalized SymmetriesVenue: virtualQuantum Matter Seminar Speaker: Marieke Van Beest (SCGP) Title: Monopoles, Scattering, and Generalized Symmetries Abstract: 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 codimension 1 surface, which ends topologically on the monopole. This symmetry defect is often noninvertible, 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. 

Speaker: Philip Boyle SmithTitle: Chiral fermionic CFTs of central charge ≤ 16Venue: virtualQuantum Matter Seminar Title: Chiral fermionic CFTs of central charge ≤ 16 Abstract: 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 nonsupersymmetric heterotic string theories, and along the way we’ll address some oftoverlooked subtleties of bosonization from the point of view of anomalies and topological phases. 

Speaker: Brandon C. RayhaunTitle: Small Bosonic CFTs, Chiral Fermionization, and Symmetry/Subalgebra DualityVenue: virtualQuantum Matter Seminar Speaker: Brandon C. Rayhaun (C. N. Yang ITP, Stony Brook University) Title: Small Bosonic CFTs, Chiral Fermionization, and Symmetry/Subalgebra Duality Abstract: 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 longstanding 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… 

Speaker: Gerald Höhn (Kansas State University) & Sven Möller (University of Hamburg)Title: Classification of SelfDual Vertex Operator Superalgebras of Central Charge at Most 24Venue: virtualQuantum Matter Seminar Speakers: Gerald Höhn (Kansas State University) & Sven Möller (University of Hamburg) Title: Classification of SelfDual Vertex Operator Superalgebras of Central Charge at Most 24 Abstract: We discuss the classfication of selfdual vertex operator superalgebras (SVOAs) of central charge 24, or in physics parlance the purely chiral 2dimensional fermionic conformal field theories with just one primary field. There are exactly 969 such SVOAs under suitable regularity assumptions and the assumption that the shorter moonshine module VB^# is the unique selfdual SVOA of central charge 23.5 whose weight1/2 and weight1 spaces vanish. We construct and classify the selfdual SVOAs by determining the 2neighbourhood graph of the selfdual (purely bosonic) VOAs of central charge 24 and also… 

Speaker: Carolyn ZhangTitle: Anomalies of (1+1)D categorical symmetriesVenue: virtualQuantum Matter Seminar Speaker: Carolyn Zhang (U Chicago) Title: Anomalies of (1+1)D categorical symmetries Abstract: 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… 

Speaker: Sona NajafiTitle: Detecting central charge in a superconducting quantum processorVenue: Hybrid G10Quantum Matter Seminar Speaker: Sona Najafi (IBM Quantum) Title: Detecting central charge in a superconducting quantum processor Abstract: 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 ShannonRenyi entropy on a local basis of a onedimensional 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… 

Speaker: Hao SongTitle: Fracton SelfStatisticsVenue: virtualQuantum Matter Seminar Title: Fracton SelfStatistics Speaker: Hao Song (ITPCAS) Abstract: 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 selfexchange statistics be naturally defined for fractons, given their complete immobility as isolated excitations? Surprisingly, we demonstrate how fractons can be exchanged, and show their selfstatistics is a key part of the characterization of fracton orders. We derive general constraints satisfied by the fracton selfstatistics in a large class of abelian fracton orders. Finally, we show the existence… 

Speaker: Subir SachdevTitle: A model of the cuprates: from the pseudogap metal to dwave superconductivity and charge orderVenue: Hybrid G10Quantum Matter Seminar Speaker: Prof. Subir Sachdev (Harvard) Title: A model of the cuprates: from the pseudogap metal to dwave superconductivity and charge order Abstract: Soon after the discovery of hightemperature superconductivity in the cuprates, Anderson proposed a connection to quantum spin liquids. But observations since then have shown that the lowtemperature phase diagram is dominated by conventional states, with a competition between superconductivity and chargeordered 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 singleband model, with small pocket Fermi surfaces of electronlike quasiparticles whose enclosed… 