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Talk

Talk


Simulating onedimensional quantum chromodynamics on a quantum computer: Realtime evolutions of tetra and pentaquarks
Christine Muschik Institute for Quantum Computing (IQC)


Five short talks  see description for talk titles

Barbara Soda Perimeter Institute for Theoretical Physics

Dalila Pirvu Perimeter Institute for Theoretical Physics
 Leonardo Solidoro, Pietro Smaniotto, Kate Brown


First observations of false vacuum decay in a BEC
Ian Moss Newcastle University

Building Quantum Simulators for QuFTs
Jorg Schmiedmayer Technical University of Vienna


Language models for simulating the dynamics of quantum systems
Juan Carrasquilla Vector Institute for Artificial Intelligence



Average SymmetryProtected Topological Phases: Construction and Detection
Jianhao Zhang Pennsylvania State University

Equivariant Higher Berry classes and chiral states
Nikita Sopenko California Institute of Technology (Caltech)


Phase diagram of the honeycomb Floquet code
DinhDuy Tran Vu University of Maryland, College Park


Staying Ahead of the Curve(ature) in Topological Phases
Julian MayMann University of Illinois UrbanaChampaign

Discrete shift and quantized charge polarization: New invariants in crystalline topological states
Naren Manjunath Perimeter Institute for Theoretical Physics

Topology of the Fermi sea: ordinary metals as topological materials
Pok Man Tam University of Pennsylvania

Exactly solvable model for a deconfined quantum critical point in 1D
Carolyn Zhang University of Chicago

Mini introductory course on topological orders and topological quantum computing
In this mini course, I shall introduce the basic concepts in 2D topological orders by studying simple models of topological orders and then introduce topological quantum computing based on Fibonacci anyons. Here is the (not perfectly ordered) syllabus.
 Overview of topological phases of matter
 Z2 toric code model: the simplest model of 2D topological orders
 Quick generalization to the quantum double model
 Anyons, topological entanglement entropy, S and T matrices
 Fusion and braiding of anyons: quantum dimensions, pentagon and hexagon identities
 Fibonacci anyons
 Topological quantum computing

Quantum Simulators of Fundamental Physics
This meeting will bring together researchers from the quantum technology, atomic physics, and fundamental physics communities to discuss how quantum simulation can be used to gain new insight into the physics of black holes and the early Universe. The core program of the workshop is intended to deepen collaboration between the UKbased Quantum Simulators for Fundamental Physics (QSimFP; https://www.qsimfp.org) consortium and researchers at Perimeter Institute and neighbouring institutions. The weeklong conference will consist of broadlyaccessible talks on work within the consortium and work within the broader community of researchers interested in quantum simulation, as well as a poster session and ample time for discussion and collaboration
Territorial Land AcknowledgementPerimeter Institute acknowledges that it is situated on the traditional territory of the Anishinaabe, Haudenosaunee, and Neutral peoples.
Perimeter Institute is located on the Haldimand Tract. After the American Revolution, the tract was granted by the British to the Six Nations of the Grand River and the Mississaugas of the Credit First Nation as compensation for their role in the war and for the loss of their traditional lands in upstate New York. Of the 950,000 acres granted to the Haudenosaunee, less than 5 percent remains Six Nations land. Only 6,100 acres remain Mississaugas of the Credit land.
We thank the Anishinaabe, Haudenosaunee, and Neutral peoples for hosting us on their land.

A lossy atom that does not decay: PT symmetry and coherent dynamics with complex energies
Yogesh Joglekar Indiana University
Isolated quantum systems, investigated a century ago, exhibit coherent, unitary dynamics. When such a system is coupled to an environment, the resulting loss of coherence is modeled by completely positive, trace preserving (CPTP) quantum maps for the density matrix. A lossy atom, when it has not decayed, exhibits a coherent dynamics that is in a distinct, new class. NonHermitian Hamiltonians with paritytime symmetry govern this class and exhibit exceptionalpoint (EP) degeneracies with topological features. After a historical introduction to PT symmetry, I will present examples of coherent, quantum dynamics in the static and Floquet regimes for such systems with a superconducting transmon (Nature Phys. 15, 1232 (2019)), ultracold atoms (Nature Comm. 10, 855 (2019)), and integrated quantum photonics (Phys. Rev. Res. 4, 013051 (2022); Nature 557, 660 (2018)) as platforms. These include topological quantum state transfer, entanglement/coherence control, and superquantum correlations. I will conclude with speculations on applicability of these ideas to quantum matter, particle physics, and strong gravity.
(* with Anthony Laing group, Kater Murch group, Le Luo group, Sourin Das group).
Zoom link: https://pitp.zoom.us/j/92391441075?pwd=QmRYSnYveUZCci9QZFcwUHBFS29QZz09

Average SymmetryProtected Topological Phases: Construction and Detection
Jianhao Zhang Pennsylvania State University
Symmetryprotected topological (SPT) phases are shortrange entanglement (SRE) quantum states which cannot be adiabatically connected to trivial product states in the presence of symmetries. Recently, it is shown that symmetryprotected shortrange entanglement can still prevail even if part of the protecting symmetry is broken by quenched disorder locally but restored upon disorder averaging, dubbed as the average symmetryprotected topological (ASPT) phases. In this talk, I will systematically construct the ASPT phases as a mixed ensemble or density matrix, which may not be realized in a clean system without any disorder. I will also design the strange correlator of the ASPT phases via a strange density matrix to detect the nontrivial ASPT state. Moreover, it is amazing that the strange correlator of ASPT can be precisely mapped to the loop correlation functions of some proper statistical loop models, with powerlaw behaviors.
Zoom link: https://pitp.zoom.us/j/91672345456?pwd=N0dNQXNmVVoybnNxYXJuWnVRME8rUT09

Equivariant Higher Berry classes and chiral states
Nikita Sopenko California Institute of Technology (Caltech)
I will talk about the generalization of Berry classes for quantum lattice spin systems. It defines invariants of topologically ordered states or families thereof. In particular, its equivariant version for 2d gapped states gives the zerotemperature Hall conductance and its various generalizations. I will also discuss the construction of chiral states realizing the topological order associated with a unitary rational vertex operator algebra for which these invariants are nontrivial
Zoom link: https://pitp.zoom.us/j/99910103969?pwd=VlVHVGRiV29iVEFyTXZyR3ovMkRaQT09

Nonadiabatically Boosting the Quantum State of a Cavity
David Long Boston College
Periodic driving is a ubiquitous tool for controlling experimental quantum systems. When the drive fields are of comparable, incommensurate frequencies, new theoretical tools are required to treat the resulting quasiperiodic time dependence. Similarly, new and surprising phenomena of topological origin may emerge in this regime, including the quantized pumping of energy from one drive field to another. I will describe how to exploit this energy pumping to coherently translate––or boost––quantum states of a cavity in the Fock basis. This protocol enables the preparation of highly excited Fock states for use in quantum metrology––one need only boost low occupation Fock states. Energy pumping, and hence boosting, may be achieved nonadiabatically as a robust edge effect associated to a topological phase. I will present a simple coupledlayer model for the phase, and briefly describe the topological classification which characterizes its robust properties.
Zoom link: https://pitp.zoom.us/j/94040881668?pwd=THh1WlIxZmZnYlp6QVRKRDhMWnk1UT09

Phase diagram of the honeycomb Floquet code
DinhDuy Tran Vu University of Maryland, College Park
The Floquet code implements a periodic sequence of twoqubit measurements to realize the topological order. After each measurement round, the instantaneous stabilizer group can be mapped to a honeycomb toric code, thus explaining the topological feature. However, the code also possesses a timecrystal order distinct from a stationary toric code – an em exchange after every cycle. In this work, we construct a continuous path interpolating between the Floquet and toric codes, focusing on the transition between the timecrystal and nontime crystal phases. We show that this transition is characterized by a diverging length scale. We also add single qubit noise to the model and obtain a twodimensional parametric phase diagram of the Floquet code.
Zoom link: https://pitp.zoom.us/j/95933569447?pwd=UkcrVHdkWERTNVIrcXdCREQ3Y1JUZz09

Entanglement Linear Response — Extracting the Quantum Hall Conductance from a Single Bulk Wavefunction and Beyond
Ruihua Fan Harvard University
In this talk, I will introduce the socalled entanglement linear response, i.e., response under entanglement generated unitary dynamics. As an application, I will show how it can be applied to certain anomalies in 1D CFTs. Moreover, I will apply it to extract the quantum Hall conductance from a wavefunction and how it embraces a previous work on the chiral central charge. This gives a new connection between entanglement, anomaly and topological response. If time permits, I will also talk about how it inspires some generalizations of the realspace Chern number formula in free fermion systems.
Zoom link: https://pitp.zoom.us/j/96535214681?pwd=MldXRkRjZ1J6WS95WXQ0cG03cWdCZz09

Staying Ahead of the Curve(ature) in Topological Phases
Julian MayMann University of Illinois UrbanaChampaign
Many topological phases of lattice systems display quantized responses to lattice defects. Notably, 2D insulators with C_n lattice rotation symmetry hosts a response where disclination defects bind fractional charge. In this talk, I will show that the underlying physics of the disclinationcharge response can be understood via a theory of continuum fermions with an enlarged SO(2) rotation symmetry. This interpretation maps the response of lattice fermions to disclinations onto the response of continuum fermions to spatial curvature. Additionally, in 3D, the response of continuum fermions to spatial curvature predicts a new type of lattice response where disclination lines host a quantized polarization. This disclinationpolarization response defines a new class of topological crystalline insulator that can be realized in lattice models. In total, these results show that continuum theories with spatial curvature provide novel insights into the universal features of topological lattice systems. In total, these results show that theories with spatial curvature provide novel insights into the universal features of topological lattice systems.
Zoom link: https://pitp.zoom.us/j/97325013281?pwd=MU5tdFYzTFljMGdaelZtNjJqbmRPZz09

Discrete shift and quantized charge polarization: New invariants in crystalline topological states
Naren Manjunath Perimeter Institute for Theoretical Physics
In this talk I will describe a topological response theory that predicts the physical manifestation of a class of topological invariants in systems with crystalline symmetry. I focus on two such invariants, the 'discrete shift' and a quantized charge polarization. Guided by theory, I discuss how these invariants can be extracted from lattice models by measuring the fractional charge at lattice disclinations and dislocations, as well as from the angular and linear momentum of magnetic flux. These methods are illustrated using the Hofstadter model of spinless fermions in a background magnetic field; they give new topological invariants in this model for the first time since the quantized Hall conductance was computed by TKNN in 1982.
Zoom link: https://pitp.zoom.us/j/93633131128?pwd=d2h4U1l0ZVU5aE1ORURkdFNSanB4dz09

Topology of the Fermi sea: ordinary metals as topological materials
Pok Man Tam University of Pennsylvania
It has long been known that the quantum ground state of a metal is characterized by an abstract manifold in the momentum space called the Fermi sea. Fermi sea can be distinguished topologically in much the same way that a ball can be distinguished from a donut by counting the number of holes. The associated topological invariant, i.e. the Euler characteristic (χ_F), serves to classify metals. Here I will survey two recent proposals relating χ_F to experimental observables, namely: (i) equaltime density/number correlations, and (ii) Andreev state transport along a planar Josephson junction. Moreover, from the perspective of quantum information, I will explain how multipartite entanglement in real space probes the Fermi sea topology in momentum space. Our works not only suggest a new connection between topology and entanglement in gapless quantum matters, but also suggest accessible experimental platforms to extract the topology in metals.
Zoom link: https://pitp.zoom.us/j/98944473905?pwd=ak5nVmd4N0pSdXpjOFM0YnFJdnJ4dz09

Exactly solvable model for a deconfined quantum critical point in 1D
Carolyn Zhang University of Chicago
We construct an exactly solvable lattice model for a deconfined quantum critical point (DQCP) in (1+1) dimensions. This DQCP occurs in an unusual setting, namely at the edge of a (2+1) dimensional bosonic symmetry protected topological phase (SPT) with ℤ2×ℤ2 symmetry. The DQCP describes a transition between two gapped edges that break different ℤ2 subgroups of the full ℤ2×ℤ2 symmetry. Our construction is based on an exact mapping between the SPT edge theory and a ℤ4 spin chain. This mapping reveals that DQCPs in this system are directly related to ordinary ℤ4 symmetry breaking critical points. Based on arXiv:2206.01222.
Zoom link: https://pitp.zoom.us/j/93794543360?pwd=Y3lidGZhRFNrUjEyMVpaNEgwTnE3QT09