Quantum Information in Quantum Gravity II

The NLTS (No Low-Energy Trivial State) conjecture of Freedman and Hastings [2014] posits that there exist families of Hamiltonians with all low energy states of non-trivial complexity (with complexity measured by the quantum circuit depth preparing the state). Our recent work https://arxiv.org/abs/2206.13228 (with Nikolas Breuckmann and Chinmay Nirkhe) proves this conjecture by showing that the recently discovered families of constant-rate and linear-distance QLDPC codes correspond to NLTS local Hamiltonians. This talk will provide background on the conjecture, its relevance to quantum many-body physics and quantum complexity theory, and touch upon the proof techniques.

Zoom link: https://pitp.zoom.us/j/94224635225?pwd=SUovNXA3MWlkRUJlcTIxV0pLQzQxdz09

Z2 lattice gauge theories (LGTs) coupled to dynamical matter show rich physics, including topological phases with anyons (toric code) and fractionalized Fermi liquids, with potential realizations in strongly correlated quantum matter. In this talk I report on recent progress — theoretical and experimental — in performing analog quantum simulations of such models. Starting from several distinct zero-dimensional building blocks I will move on to discuss extensions to extended 1D and 2D systems, including the realization of the plaquette operators in 2D. Next I will discuss how experimental imperfects, such as gauge-symmetry breaking errors, impact quantum simulations, and how they can be overcome. Then I will show how the insights gained lead us to an inherently stable protocol for quantum simulations of Z2 LGTs with dynamical matter with existing Rydberg tweezer arrays. I will close with an outlook and by discussing possible near-term experimental goals ranging from disorder-free localization to finite-temperature deconfinement transitions.

Zoom link:  https://pitp.zoom.us/j/91839919649?pwd=Tm1uOVljWUV3R05aUkxFVkFzN3lIZz09

As a recent combination of two strong global leaders in quantum computing, Honeywell Quantum Solutions and Cambridge Quantum, Quantinuum integrates quantum hardware and software, including solutions for drug discovery, materials science, finance, and other applications. Quantinuum aims to be a center of gravity for quantum computing, supporting collaboration across the ecosystem. For this we have also developed “TKET”, an open-source architecture-agnostic quantum software stack and ‘best in class’ compiler. This enables our partners, collaborators and clients to effortlessly work across multiple platforms and tackle some of the most intriguing and important problems in quantum computing. 

Bio: Dr. Mark Jackson is the Senior Quantum Evangelist at Quantinuum. He received his B.S. in Physics and Mathematics from Duke University and Ph.D. in Theoretical Physics from Columbia University. He then spent 10 years researching superstring theory and cosmology, co-authoring almost 40 technical articles. To promote the public understanding of science, he founded the science crowdfunding platform Fiat Physica and non-profit Science Partnership Fund. He is Adjunct Faculty at Singularity University and a Director of Astronomers Without Borders.

Zoom link: https://pitp.zoom.us/j/98433088425?pwd=UzgwcGpUYnBKNzJmMnQ1ZVNOdGVXZz09

The phase diagram of a material is of central importance in describing the properties and behaviour of a condensed matter system. Indeed, the study of quantum phase transitions has formed a central part of 20th and 21st Century physics. We examine the complexity and computability of determining the phase diagram of a general Hamiltonian. We show that in the worst case it is uncomputable and in more restricted cases, where the Hamiltonian is “better behaved”, it remains computationally intractable even for a quantum computer. Finally, we take a look at the relations between the Renormalization Group and uncomputable Hamiltonians.

Zoom Link: https://pitp.zoom.us/j/96048987715?pwd=WGtwWk1SUnFsanNIVTZVYjNmbTh3Zz09

In this talk, I will present three algorithms that address distinct variants of the problem of testing quantum states. First, I will discuss the problem of statistically testing whether an unknown quantum state is a matrix product state of certain bond dimension or it is far from all such states. Next, I will demonstrate a method for testing whether a bipartite quantum state, shared between two parties, corresponds to the ground state of a given gapped local Hamiltonian. Finally, I will present a scheme for verifying that a machine learning model of an unknown quantum state has high overlap with the actual state.

Zoom Link: https://pitp.zoom.us/j/99250127489?pwd=UCtXUi9zMzJZamppT29DbWtJcWU3Zz09