Format results
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Talk
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Protective Measurement and Ergodicity
Yakir Aharonov Chapman University
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Sudden Sharp Forces and Nonlocal Interactions
Yakir Aharonov Chapman University
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Talk
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Gravity Dual of Quantum Information Metric
Tadashi Takayanagi Yukawa Institute for Theoretical Physics
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A new perspective on holographic entanglement
Matthew Headrick Brandeis University
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Universal holographic description of CFT entanglement entropy
Thomas Faulkner University of Illinois Urbana-Champaign
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Geometric Constructs in AdS/CFT
Veronika Hubeny University of California, Davis
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Do black holes create polyamory
Jonathan Oppenheim University College London
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Tensor Network Renormalization and the MERA
Glen Evenbly Georgia Institute of Technology
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Entanglement renormalization for quantum fields
Jutho Haegeman Ghent University
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Holographic quantum error-correcting codes: Toy models for the bulk/boundary correspondence
Fernando Pastawski California Institute of Technology
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Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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From nonlocality transitivity to resource marginal problems and back
Yeong-Cherng Liang National Cheng Kung University
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Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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Symmetry enforced entanglement in maximally mixed states
Subhayan Sahu Perimeter Institute for Theoretical Physics
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Universal quantum computation in two dimensions by converting between the toric code and a non-abelian quantum double
Margarita Davydova Massachusetts Institute of Technology (MIT)
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Quantum Information in Quantum Gravity II
Quantum Information in Quantum Gravity II -
Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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From nonlocality transitivity to resource marginal problems and back
Yeong-Cherng Liang National Cheng Kung University
In this talk, I shall recall the nonlocality transitivity problem, which concerns the possibility of inferring the Bell-nonlocality of certain marginals in a multipartite scenario based on other given marginals. Then, I explain how considering this problem has led to a more general class of problems known as resource marginal problems (RMPs). More precisely, RMPs concern the possibility of having a resource-free target subsystem compatible with a given collection of marginal density matrices. We briefly discuss how a resource theory for a collection of marginal density matrices naturally arises from any given RMP and present some general features of such a theory. After that, we focus on a special case of RMPs known as the entanglement transitivity problems and explain how our progress on this problem has led to progress in the original nonlocality transitivity problem.
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Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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Lecture - Quantum Theory, PHYS 605
Bindiya Arora Perimeter Institute for Theoretical Physics
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Symmetry enforced entanglement in maximally mixed states
Subhayan Sahu Perimeter Institute for Theoretical Physics
Entanglement in quantum many-body systems is typically fragile to interactions with the environment. Generic unital quantum channels, for example, have the maximally mixed state with no entanglement as their unique steady state. However, we find that for a unital quantum channel that is `strongly symmetric', i.e. it preserves a global on-site symmetry, the maximally mixed steady state in certain symmetry sectors can be highly entangled. For a given symmetry, we analyze the entanglement and correlations of the maximally mixed state in the invariant sector (MMIS), and show that the entanglement of formation and distillation are exactly computable and equal for any bipartition. For all Abelian symmetries, the MMIS is separable, and for all non-Abelian symmetries, the MMIS is entangled. Remarkably, for non-Abelian continuous symmetries described by compact semisimple Lie groups (e.g. SU(2)), the bipartite entanglement of formation for the MMIS scales logarithmically ∼logN with the number of qudits N.
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Emergent symmetries and their application to logical gates in quantum LDPC codes
In this talk, I’ll discuss the deep connection between emergent k-form symmetries and transversal logical gates in quantum low-density parity-check (LDPC) codes. I’ll then present a parallel fault-tolerant quantum computing scheme for families of homological quantum LDPC codes defined on 3-manifolds with constant or almost-constant encoding rate using the underlying higher symmetries in our recent work. We derive a generic formula for a transversal T gate on color codes defined on general 3-manifolds, which acts as collective non-Clifford logical CCZ gates on any triplet of logical qubits with their logical-X membranes having a Z2 triple intersection at a single point. The triple intersection number is a topological invariant, which also arises in the path integral of the emergent higher symmetry operator in a topological quantum field theory (TQFT): the (Z2) 3 gauge theory. Moreover, the transversal S gate of the color code corresponds to a higher-form symmetry supported on a codimension-1 submanifold, giving rise to exponentially many addressable and parallelizable logical CZ gates. Both symmetries are related to gauged SPT defects in the (Z2) 3 gauge theory. We have then developed a generic formalism to compute the triple intersection invariants for general 3- manifolds. We further develop three types of LDPC codes supporting such logical gates with constant or almost-constant encoding rate and logarithmic distance. Finally, I’ll point out a connection between the gauged SPT defects in the 6D color code and a recently discovered non-Abelian self-correcting quantum memory in 5D. Reference: arXiv:2310.16982, arXiv:2208.07367, arXiv:2405.11719. -
Universal quantum computation in two dimensions by converting between the toric code and a non-abelian quantum double
Margarita Davydova Massachusetts Institute of Technology (MIT)
In this talk, I will explain how to implement fault-tolerant non-Clifford gates in copies of toric code in two dimensions achieved by transiently switching to a non-Abelian topologically ordered phase by expanding earlier results by Bombin [arXiv.1810.09571] and Brown [SciAdv.aay4929]. This addresses the challenge of performing universal fault-tolerant quantum computation in purely two spatial dimensions and shows a new approach to quantum computation using non-Abelian phases. This talk is based on upcoming work in collaboration with A. Bauer, B.Brown, J. Magdalena de la Fuente, M. Webster and D. Williamson. -
Fault tolerance with the ZX-calculus and fusion complexes
Naomi Nickerson PSI Quantum
Quantum error correction methods for qubit technologies such as ions, photons, or superconducting qubits can appear very different at first glance. Moreover, as more detailed error models are accounted for, the relationship to the abstract models of fault tolerance can appear to become more distant. In this talk I will discuss two unifying frameworks which connect hardware specific models more closely to the underlying code structures, which can help enable QEC development. First I will introduce a unifying framework for fault tolerance based on the ZX calculus (arXiv:2303.08829) and show how it allows us to view circuit-based, measurement-based, fusion-based quantum computation, and Floquet codes as different flavors of the same underlying stabilizer fault-tolerance structure. Secondly I will introduce fusion complexes (arXiv:2308.07844) which allows a topological interpretation of fault tolerance even under circuit level error models. Both of these frameworks are tools that can aid in the design of quantum error correction methods under hardware-focussed models, and I will give some examples of this applied to the design of photonic architectures. -
Landscape of Measurement-Prepared Tensor Networks and Decohered Non-Abelian Topological Order
Ruben Verresen Harvard University
What is the structure of many-body quantum phases and transitions in the presence of non-unitary elements, such as decoherence or measurements? In this talk we explore two new directions. First, recent works have shown that even if one starts with an ideal preparation of topological order such as the toric code, decoherence can lead to interesting mixed states with subtle phase transitions [e.g., Fan et al, arXiv:2301.05689]. Motivated by a recent experimental realization of non-Abelian topological order [Iqbal et al, Nature 626 (2024)], we generalize this to decohered non-Abelian states, based on work with Pablo Sala and Jason Alicea [to appear]. Second, we study whether and how one can prepare pure states which are already detuned from ideal fixed-point cases---with tunable correlation lengths. This turns out to be possible for large classes of tensor network states which can be deterministically prepared using finite-depth measurement protocols. This is based on two recent works with Rahul Sahay [arXiv:2404.17087; arXiv:2404.16753].