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5/27/24, 9:00 AMOpening/Closing Remarks
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Matthew Fisher (UC Santa Barbara)5/27/24, 9:15 AMConference Talk
"Optimal fault tolerant error correction thresholds for CCS codes are traditionally obtained via mappings to classical statistical mechanics models, for example the 2d random bond Ising model for the 1d repetition code subject to bit-flip noise and faulty measurements. Here, we revisit the 1d repetition code, and develop an exact “stabilizer expansion” of the full time evolving density matrix...
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Tarun Grover (UC San Diego)5/27/24, 11:00 AMConference Talk
Ground states as well as Gibbs states of many-body quantum Hamiltonians have been studied extensively for some time. In contrast, the landscape of mixed states that do not correspond to a system in thermal equilibrium is relatively less explored. In this talk I will motivate a rather coarse characterization of mixed quantum many-body states using the idea of "separability", i.e., whether a...
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Shengqi Sang (Perimeter Institute)5/27/24, 2:00 PMConference Talk
For quantum phases of Hamiltonian ground states, the energy gap plays a central role in ensuring the stability of the phase as long as the gap remains finite. In this talk we introduce Markov length, the length scale at which the quantum conditional mutual information (CMI) decays exponentially, as an equally essential quantity characterizing mixed-state phases and transitions. For a state...
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Tsung-Cheng Peter Lu (Perimeter Institute)5/27/24, 3:30 PMConference Talk
Long-range entangled mixed states are exotic many-body systems that exhibit intrinsically quantum phenomena despite extensive classical fluctuations. In the first part of the talk, I will show how they can be efficiently prepared with measurements and unitary feedback conditioned on the measurement outcome. For example, symmetry-protected topological phases can be universally converted into...
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Liang Fu (Massachusetts Institute of Technology (MIT))5/28/24, 9:00 AMConference Talk
I will show the existence of a universal upper bound on the energy gap of topological states of matter, such as (integer and fractional) Chern insulators, quantum spin liquids and topological superconductors. This gap bound turns out to be fairly tight for the Chern insulator states that were predicted and observed in twisted bilayer transition metal dichalcogenides. Next, I will show a...
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Daniel Ranard (Massachusetts Institute of Technology (MIT))5/28/24, 11:00 AMConference Talk
Two gapped ground states of lattice Hamiltonians are in the same quantum phase of matter, or topological phase, if they can be connected by a constant-depth circuit. It is conjectured that in two spatial dimensions, two gapped ground states with gappable boundary are in the same phase if and only if they have the same anyon contents, which are described by a unitary modular tensor category. We...
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Xie Chen (California Institute of Technology)5/28/24, 2:00 PMConference Talk
Entanglement in many-body quantum systems is notoriously hard to characterize due to the exponentially many parameters involved to describe the state. On the other hand, we are usually not interested in all the microscopic details of the entanglement attern but only some of its global features. It turns out, quantum circuits of different levels of complexity provide a useful way to establish a...
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Zhi Li (Perimeter Institute)5/28/24, 3:30 PMConference Talk
It is commonly believed that logical states of quantum error-correcting codes have to be highly entangled such that codes capable of correcting more errors require more entanglement to encode a qubit. Here we show that this belief may or may not be true depending on a particular code. To this end, we characterize a tradeoff between the code distance d quantifying the number of correctable...
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Michael Levin (University of Chicago)5/29/24, 9:00 AMConference Talk
I will discuss recent progress in understanding entanglement-based probes of 2D topological phases of matter. These probes are supposed to extract universal topological information from a many-body ground state. Specifically, I will discuss (1) the topological entanglement entropy, which is supposed to give information about the number of anyon excitations, and (2) the modular commutator,...
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Hsin-Yuan (Robert) Huang (Google Quantum AI)5/29/24, 11:00 AMConference Talk
Certifying that an n-qubit state synthesized in the lab is close to the target state is a fundamental task in quantum information science. However, existing rigorous protocols either require deep quantum circuits or exponentially many single-qubit measurements. In this work, we prove that almost all n-qubit target states, including those with exponential circuit complexity, can be certified...
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Sarang Gopalakrishnan (Princeton University)5/29/24, 3:30 PMConference Talk
The steady states of dynamical processes can exhibit stable nontrivial phases, which can also serve as fault-tolerant classical or quantum memories. For Markovian quantum (classical) dynamics, these steady states are extremal eigenvectors of the non-Hermitian operators that generate the dynamics, i.e., quantum channels (Markov chains). However, since these operators are non-Hermitian, their...
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Vedika Khemani (Stanford University)5/30/24, 9:00 AMConference Talk
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Brian Swingle (Brandeis University)5/30/24, 11:00 AMConference Talk
We discuss families of approximate quantum error correcting codes which arise as the nearly-degenerate ground states of certain quantum many-body Hamiltonians composed of non-commuting terms. For exact codes, the conditions for error correction can be formulated in terms of the vanishing of a two-sided mutual information in a low-temperature thermofield double state. We consider a notion of...
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Marcos Rigol (Penn State University)5/30/24, 2:00 PMConference Talk
Quantum-chaotic systems are known to exhibit eigenstate thermalization and to generically thermalize under unitary dynamics. In contrast, quantum-integrable systems exhibit a generalized form of eigenstate thermalization and need to be described using generalized Gibbs ensembles after equilibration. I will discuss evidence that the entanglement properties of highly excited eigenstates of...
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Meenu Kumari (National Research Council Canada)5/30/24, 3:30 PMConference Talk
Quantum many-body scars (QMBS) are atypical eigenstates of chaotic systems that are characterized by sub-volume or area law entanglement as opposed to the volume law present in the bulk of the eigenstates. The term, QMBS, was coined using heuristic correlations with quantum scars - eigenstates with high probability density around unstable classical periodic orbits in quantum systems with a...
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Ruben Verresen (Harvard / MIT)5/31/24, 9:00 AMConference Talk
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...
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Naomi Nickerson (PSI Quantum)5/31/24, 11:00 AMConference Talk
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...
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Margarita Davydova (Massachusetts Institute of Technology (MIT))5/31/24, 1:00 PMConference Talk
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...
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Guanyu Zhu (IBM)5/31/24, 2:30 PMConference Talk
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
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rate using the underlying higher symmetries in our... -
5/31/24, 3:30 PMOpening/Closing Remarks
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Dr Ramanjit Sohal (Princeton University)Poster
We propose a general framework for studying two-dimensional (2D) topologically ordered states subject to local correlated errors and show that the resulting mixed-state can display intrinsically mixed-state topological order (imTO) -- topological order which is not expected to occur in the ground state of 2D local gapped Hamiltonians. Specifically, we show that decoherence, previously...
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Mr Ayush Raj (Purdue University)Poster
We develop a framework that can obtain non-integer moments of density matrices via analytically continuing from integer moments measured by the randomized measurement protocol. We identify the best performing analytic continuation techniques that are robust against noisy input data, and demonstrate their effectiveness in the case study of von Neumann entanglement entropy. As a...
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Dr Cheng-Ju LinPoster
We consider a class of states which can be constructed and related by the su(2) algebra. Some notable realizations are the Dicke states and the su(2) scar states. By utilizing the su(2) algebra relation and Knill-Laflamme condition, we show that some choices of the states form an [[N,k,d,ε]] approximate quantum error correcting code, where ε~O(2^{k+d}d N^{α-1}) for α < 1. This class of codes...
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Mr Hiroki Sukeno (Stony Brook University)Poster
In quantum many-body spin systems, the interplay between the entangling effect of multi-qubit Pauli measurements and the disentangling effect of single-qubit Pauli measurements may give rise to two competing effects. By introducing a randomized measurement pattern with such bases, a phase transition can be induced by altering the ratio between them. In this work, we numerically investigate a...
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Jinmin Yi (Perimeter Institute), Weicheng Ye (University of British Columbia)Poster
We establish rigorous connections between quantum circuit complexity and approximate quantum error correction (AQEC) properties, covering both all-to-all and geometric scenarios including lattice systems. To this end, we introduce a type of code parameter that we call subsystem variance, which is closely related to the optimal AQEC precision. Our key finding is that if the subsystem variance...
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Mr Aswin Parayil Mana (Stony Brook University)Poster
Calderbank-Shor-Steane (CSS) codes are a class of quantum error correction codes that contains the toric code and fracton models. A procedure called foliation defines a cluster state for a given CSS code. We demonstrate the so-called anomaly inflow between CSS codes and corresponding foliated cluster states by explicitly showing the equality of the gauge transformations of the bulk and...
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Mr Zhehao Zhang (UC Santa Barbara)Poster
Quantum many-body states in the presence of decoherence can host a variety of orders, as diag-
nosed by measures of correlations in multiple copies of the decohered state. Here, we argue that
some of these measures, such as the “strange correlator” in decohered symmetry protected topo-
logical (SPT) states are directly related to the ability to use the decohered state as a resource...
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Zhu-Xi Luo (Harvard University)Poster
Ground states of topological phases have robust degeneracy, or in modern language, they spontaneously break the strong 1-form symmetries to nothing. When disorder or decoherence is present, strong symmetries can be explicitly broken to weak/average symmetries. The resultant mixed state can also exhibit new patterns of spontaneous 1-form symmetry breaking from strong to weak (SWSSB) and from...
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Mincheol Park (Harvard University)Poster
Reliable quantum computation requires systematic identification and correction of errors that occur and accumulate in data qubits of quantum hardware. To diagnose such errors, standard quantum error correction protocols utilize global error syndrome information across the system obtained by mid-circuit measurements of ancilla qubits [1]. However, in certain state-of-the-art architectures [2],...
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Prof. Xiao Yan Xu (School of Physics and Astronomy, Shanghai Jiao Tong University)Poster
Many-body entanglement unveils additional aspects of quantum matter and offers insights into strongly correlated physics. While ground-state entanglement has received much attention in the past decade, the study of mixed-state quantum entanglement using negativity in interacting fermionic systems remains largely unexplored. We demonstrate that the partially transposed density matrix of...
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Emiliia Dyrenkova (Institute for Quantum Computing)Poster
As we move towards the era of quantum computers with 1000+ qubits, the most promising application able to harness the potential of such devices is quantum simulation. Simulating fermionic systems is both a well-formulated problem with clear real-world applications and a computationally challenging task. In order to simulate a system of fermions on a quantum computer, one has to map the...
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Jordi A. Montana LopezPoster
Quantum systems can not be efficiently simulated classically due to the presence of entanglement and nonstabilizerness, also known as quantum magic. Here we study the generation of magic under evolution by a quantum circuit.
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To be able to provide exact solutions, we focus on the dual-unitary XXZ model and a measure of magic called stabilizer Rényi entropy (SRE). Moreover, we focus also on... -
Eric Schultz (Purdue University)Poster
Dynamical entropies characterize chaos within a dynamical system. One such candidate for quantum dynamical systems is the Alicki-Fannes-Lindblad (AFL) entropy. AFL entropy has been used to study certain quantum systems with a chaotic classical limit, where it recovers the classical Kolmogorov-Sinai entropy. However, some of these systems are not quantum chaotic, which bring into question...
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Dr Ayana Sarkar (Université de Sherbrooke)Poster
We introduce Fermionic Machine Learning (FermiML), a novel machine learning framework that leverages the principles of fermionic quantum computation. At the heart of FermiML, lies parameterized matchgate circuits, a restricted class of quantum circuits closely mirroring the behavior of free fermions in one-dimension. The FermiML framework enables the creation of "fermionic" versions of various...
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Sajant Anand (University of California, Berkely)Poster
Accurately calculating microscopic details of non-equilibrium transport of conserved quantities in interacting quantum spin chains is difficult due to the growth of entanglement, limiting the applicability of standard tensor network algorithms. Here we introduce a novel tensor algorithm for accurately evolving mixed states and operators with long-range Hamiltonians, keeping properties...
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Jacob Hauser (UC Santa Barbara)Poster
Quantum information can be protected from noise by repeated syndrome measurements, even if these measurements themselves are faulty. A decoding transition occurs at a particular noise rate, beyond which information is lost. Recently, it has been shown that the decoding transition in the surface code after one round of measurements can be understood via intrinsic properties of the physical...
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Mao Tian Tan (Asia Pacific Center for Theoretical Physics)Poster
In recent years, analytically tractable models of quench and Floquet dynamics have been constructed in two-dimensional conformal field theories by considering the time evolution generated by a family of inhomogeneous Hamiltonians which includes the sine-squared-deformed (SSD) Hamiltonian where the energy density profile is given by a sine-squared function.
When the thermal state is...
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Dr Jacob Bridgeman (Ghent University)Poster
Topological subsystem codes in three spatial dimensions allow for quantum error correction with no time overhead, even in the presence of measurement noise. The physical origins of this single-shot property remain elusive, in part due to the scarcity of known models. To address this challenge, we provide a systematic construction of a class of topological subsystem codes in three dimensions...
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Hyunsoo Ha (Princeton)Poster
The competition between scrambling and projective measurements can lead to measurement-induced entanglement phase transitions (MIPT). In this work, we show that the universality class of the MIPT drastically alters when the system is coupled to a diffusing conserved density. Specifically, we consider a 1+1d random Clifford circuit locally monitored by classically diffusing particles ...
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Pablo SALA DE TORRES SOLANOT (California Institute of Technology)Poster
Previous works have found that subjecting a ground state of the Toric Code to different types of quantum channels lead to a critical error threshold. This signals the error rate beyond which the Toric Code stops being a good quantum memory. Here we investigate the effects of decoherence on non-abelian topological order, including the case of D4 topological order which was recently...
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Leonardo A. Lessa (Perimeter Institute)Poster
Quantum entanglement measures of many-body states have been increasingly useful to characterize phases of matter. Here we explore the surprising connection between symmetry-protected topology (SPT) and separability of their boundary mixed states. More specifically, we consider lattice systems in d space dimensions with anomalous symmetry G, where the anomaly is characterized by a bulk SPT...
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Mohammad Ayyash (Institute for Quantum Computing / University of Waterloo)Poster
Nonlinear interactions play a fundamental role in generating and manipulating valuable quantum-mechanical
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phenomena. There is currently a growing interest in the interaction between a qubit and an oscillator through
multiphoton processes. This interaction serves various purposes, such as the creation of nonclassical states in the
oscillator or the use of the oscillator as a coupling element... -
Ralph Jason Costales (Perimeter Institute for Theoretical Physics)Poster
Measurement and conditional unitary feedback can convert certain symmetry-protected topological orders to long-range entangled mixed states, whose exact characterization remains elusive. Here we show that these mixed states can be mapped to the GHZ state via a local quantum channel realized by a series of measurements followed by a truncated version of the Minimal Weight Perfect Matching...
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Andrew Keefe (University of Massachusetts Lowell)Poster
Dynamics of simple quantum systems can serve as powerful probes of many-body correlations in their environment. For instance, it has been shown that open systems in contact with critical environments exhibit strictly Markovian dynamics [1, 2]. However, a direct experimental observation of such dynamical signatures can be particularly challenging, since they manifest at very short time scales...
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Dr Yasar Atas (IQC)Poster
Quantum chromodynamics (QCD)—the theory of quarks and gluons—has been studied for decades, but it is yet to be fully understood. A recent example is the prediction and experimental discovery of tetraquarks, which opened a new research field. Crucially, numerous unsolved questions regarding the standard model can exclusively be addressed by nonperturbative calculations. Quantum computers can...
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Mr Amit Anand (IQC, University of Waterloo, Canada)Poster
The emergence of classical chaos from an underlying quantum mechanics poses a challenge for the Bohr correspondence principle. We present an infinite family of quantum dynamics that never resembles the analogous classical chaotic dynamics, irrespective of dimension. These take the form of stroboscopic unitary evolutions in the quantum kicked top that act as the identity after a finite number...
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Chengshu LiPoster
We construct a hetero-nucleus Rydberg atom system which harbors emergent supersymmetry (SUSY) at its critical point, via the well-established identification of SUSY and two-dimensional tricritical Ising criticality. After discussing the necessity of using hetero-nucleus Rydberg atoms, we employ numerical calculations and conformal field theoretical results to corroborate the existence of SUSY,...
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Tiangang Zhou (Tsinghua University)Poster
The concept of information scrambling elucidates the dispersion of local information in quantum many-body systems, offering insights into various physical phenomena such as wormhole teleportation. This phenomenon has spurred extensive theoretical and experimental investigations. Among these, the size-winding mechanism emerges as a valuable diagnostic tool for optimizing signal detection. We...
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Dr Benedikt Placke (Rudolf Peierls Centre for Theoretical Physics, University of Oxford)Poster
Subsystem symmetries underpin many unconventional dynamical phenomena in unitary dynamics of matter. Here, we investigate their effect on non-unitary quantum many-body dynamics. Specifically, we consider stochastic, measurement-only circuits based on subsystem codes with subsystem symmetries, with the Bacon-Shor code and various generalizations as guiding examples. Perhaps most strikingly, we...
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Dr Cheng-Ju LinPoster
The ongoing developments of analog and digital quantum simulators spark the interest in defining and classifying mixed-state phases of matter out of equilibrium. This consideration motivates the recent interest in symmetry-protected topological mixed states. In this work, we explore the physics of open system dynamics whose non-equilibrium steady states are the decohered cluster states —-...
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Zhou Yang (Cornell University)Poster
Quantum error correction (QEC) codes protect quantum information from errors due to decoherence. Many of them also serve as prototypical models for exotic topological quantum matters. Investigating the behavior of the QEC codes under decoherence sheds light on not only the codes' robustness against errors but also new out-of-equilibrium quantum phases driven by decoherence. The phase...
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Dr Jonathon Riddell (Nottingham University)Poster
A quantum many body system having spectral correlations that agree with random matrix theory is the most general defining feature of the system being quantum chaotic. Proving a system has this property is notoriously difficult. Despite this a rigorous proof has been achieved for dual-unitary circuit models, a special class of local quantum circuits that remain unitary when swapping the roles...
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Mr Yale Cheng (Perimeter Institute)Poster
The bipartite entanglement entropy is a measure of quantum correlations and is conjectured to be a probe of quantum chaos when computed for random eigenstates of a physical Hamiltonian. We derive the entanglement entropy of random states with a fixed particle number in any system of indistinguishable particles including fermions, bosons, spin systems and mixtures thereof. Remarkably, we are...
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Dr Guglielmo Lami (University of Cergy-Pontoise)Poster
We present a novel classical algorithm designed to learn the stabilizer group -- namely the group of Pauli strings for which a state is a $\pm 1$ eigenvector -- of a given Matrix Product State (MPS). The algorithm is based on a clever and theoretically grounded biased sampling in the Pauli (or Bell) basis. Its output is a set of independent stabilizer generators whose total number is directly...
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Yizhi YouPoster
In this work, we aim to establish a connection between exotic quantum mixed states with long-range or SPT order from the perspective of purification. We will demonstrate that the quantum ordering in a mixed state can be visualized from its purification, wherein the purified state exhibits conditional long-range order and measurement-induced mutual information. In particular, we will elucidate...
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Grace Sommers (Princeton University)Poster
In chaotic quantum systems, the entanglement of a region A can be described in terms of the surface tension of a spacetime membrane pinned to the boundary of A. Here, we interpret the tension of this entanglement membrane in terms of the rate at which information "flows" across it. For any orientation of the membrane, one can define (generically nonunitary) dynamics across the membrane;...
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