Quantum mechanics redefines information and its fundamental properties. Researchers at Perimeter Institute work to understand the properties of quantum information and study which information processing tasks are feasible, and which are infeasible or impossible. This includes research in quantum cryptography, which studies the trade-off between information extraction and disturbance, and its applications. It also includes research in quantum error correction, which involves the study of methods for protecting information against decoherence. Another important side of the field is studying the application of quantum information techniques and insights to other areas of physics, including quantum foundations and condensed matter.
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Probing 2D invertible phases with replica permutations
Michael Levin
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Non-perturbative constraints on phase diagrams of non-equilibrium systems
Tarun Grover - University of California, San Diego
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Strong-to-weak $U(1)$ Symmetry Breaking in Open System Dynamics
Matthew Fisher - University of California, Santa Barbara
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Decohered Gibbs states
Sarang Gopalakrishnan
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Conference TalkDressed logical operators in mixed state quantum matter
Curt von Keyserlingk
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Circuit-based characterization of finite-temperature quantum phases
Shengqi Sang - Stanford University
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Measuring many observables from very few thermal states
Chi-Fang (Anthony) Chen
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Symmetry enforced entanglement in mixed states
Subhayan Sahu - Perimeter Institute for Theoretical Physics
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Unlearnable Phases of Matter
Yijian Zou - Perimeter Institute for Theoretical Physics
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Braided Fusion Complexes: An Algebraic Theory of Gapped Abelian Phases
I will introduce the notion of a braided fusion complex --- a mathematical structure designed to encapsulate the universal fusion and braiding data of abelian excitations of gapped quantum phases. This structure provides a framework for characterizing and classifying fracton phases of matter. -
Probing 2D invertible phases with replica permutations
Michael Levin
I will discuss a class of probes of 2D invertible phases of matter based on replica permutation operators. These probes are defined by introducing multiple replicas of a many-body system and evaluating expectation values of permutation operators acting in different spatial regions. A notable example… -
Non-perturbative constraints on phase diagrams of non-equilibrium systems
Tarun Grover - University of California, San Diego
In this talk I will discuss constraints on renormalization group (RG) flows and the stability of phases in nonequilibrium systems using information-theoretic inequalities, with examples drawn from both quantum and classical settings. The central quantity underlying these constraints is the… -
Strong-to-weak $U(1)$ Symmetry Breaking in Open System Dynamics
Matthew Fisher - University of California, Santa Barbara
n generic open quantum systems, universal dynamical processes tend to exhibit classicality - dissipation washes out quantum effects. Here I consider open quantum dynamics in the presence of a global U(1) symmetry. In mixed states, this symmetry can be either strong or weak, and distinct dynamical… -
Extensive Long-Range Magic in Non-Abelian Topological Orders
Sagar Vijay
I discuss how the low-energy states of non-Abelian topological orders possess extensive magic which is long-ranged, and cannot be eliminated by a constant-depth local unitary circuit. This refines conventional notions of complexity beyond the linear circuit depth which is required to prepare any… -
Decohered Gibbs states
Sarang Gopalakrishnan
I will discuss the mixed-state phase diagrams of decohered Gibbs states. I will argue, in particular, that commuting Gibbs states at nonzero temperature lie in the interior of mixed-state phases. -
Conference TalkDressed logical operators in mixed state quantum matter
Curt von Keyserlingk
We describe how to construct emergent strong higher-form symmetries in mixed quantum states that act unitarily on Hilbert space. Our construction uses (quasi-)local recovery channels from quantum error correction to some nearby simple (stabilizer or more general commuting projector) model. We prove… -
Circuit-based characterization of finite-temperature quantum phases
Shengqi Sang - Stanford University
Quantum phases at zero temperature can be defined as equivalence classes under local unitary transformations: two ground states are in the same phase if they can be transformed into each other via a local unitary circuit. In this talk, I will discuss how to generalize this circuit-based… -
Measuring many observables from very few thermal states
Chi-Fang (Anthony) Chen
We present a general protocol for efficiently estimating M observables from only log(M) copies of a Gibbs state, given access to its Hamiltonian. -
Quantum Industry Networking Event
Are you thinking about transitioning to Industry? Join the Quantum Industry Networking Event to hear from speakers who have transitioned from academia to quantum industry and participate in the speed networking session following their talks. **Confirmed guests include:** Aggie Branczyk – Quantum… -
Symmetry enforced entanglement in mixed states
Subhayan Sahu - Perimeter Institute for Theoretical Physics
Entanglement in quantum many-body systems is typically fragile to interactions with the environment. Strongly symmetric interactions, i.e. those that preserve a system's symmetry, however, can enforce non-trivial quantum entanglement patterns. We show that the highly mixed steady states of strongly… -
Unlearnable Phases of Matter
Yijian Zou - Perimeter Institute for Theoretical Physics
We identify fundamental limitations in machine learning by demonstrating that non-trivial mixed-state phases of matter are computationally hard to learn. Focusing on unsupervised learning of distributions, we show that autoregressive neural networks fail to learn global properties of distributions…