Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1905.11430 · Physical Review Letters

Treelike Interactions and Fast Scrambling with Cold Atoms

Gregory S. Bentsen, Tomohiro Hashizume, Anton S. Buyskikh, Emily J. Davis, Andrew J. Daley, Steven S. Gubser, Monika Schleier-Smith

Published Sep 23, 2019• 81 citations
arXivHTMLPDF

Abstract

We propose an experimentally realizable quantum spin model that exhibits fast scrambling, based on nonlocal interactions that couple sites whose separation is a power of 2. By controlling the relative strengths of deterministic, nonrandom couplings, we can continuously tune from the linear geometry of a nearest-neighbor spin chain to an ultrametric geometry in which the effective distance between spins is governed by their positions on a tree graph. The transition in geometry can be observed in quench dynamics, and is furthermore manifest in calculations of the entanglement entropy. Between the linear and treelike regimes, we find a peak in entanglement and exponentially fast spreading of quantum information across the system. Our proposed implementation, harnessing photon-mediated interactions among cold atoms in an optical cavity, offers a test case for experimentally observing the emergent geometry of a quantum many-body system.

DOI
10.1103/physrevlett.123.130601

Related papers

Tunable geometries from a sparse quantum spin network

Gregory S. Bentsen, Tomohiro Hashizume, Emily J. Davis +3 more

Nonlocal light-mediated interactions between cold atoms coupled to the mode of an optical cavity present unique prospects for simulating the quantum dynamics of strongly-interacting many-body systems. In a recent publication, we introduced a tunable, nonlocal sparse spin network that can be engineered in near-term single-mode cavity QED platforms.1 In this companion paper, we study this spin network in detail and pedagogically review its basic dynamical properties, providing theoretical details and calculations that expand on the statements made in our original publication. We show that the network exhibits two distinct notions of emergent geometry - linear and treelike - that can be accessed using a single tunable parameter. In either of these two extreme limits, we find a succinct description of the resulting dynamics in terms of two distinct metrics on the network, encoding a notion of either linear or treelike distance between spins. We also show that the network can be mapped in these two extreme limits onto exactly solvable models: a linear Heisenberg spin chain in one limit, and a Dyson hierarchical model in the other. These observations highlight the essential role played by the geometry of the interaction structure in determining a system's dynamics, and raise prospects for novel studies of nonlocal and highly chaotic quantum dynamics in near-term experiments.

Optical and Quantum Sensing and Precision Metrology II•Feb 25, 2020•2 citations

Deterministic Fast Scrambling with Neutral Atom Arrays

Tomohiro Hashizume, Gregory S. Bentsen, Sebastian Weber +1 more

Fast scramblers are dynamical quantum systems that produce many-body entanglement on a timescale that grows logarithmically with the system size N. We propose and investigate a family of deterministic, fast scrambling quantum circuits realizable in near-term experiments with arrays of neutral atoms. We show that three experimental tools-nearest-neighbor Rydberg interactions, global single-qubit rotations, and shuffling operations facilitated by an auxiliary tweezer array-are sufficient to generate nonlocal interaction graphs capable of scrambling quantum information using only O(logN) parallel applications of nearest-neighbor gates. These tools enable direct experimental access to fast scrambling dynamics in a highly controlled and programmable way and can be harnessed to produce highly entangled states with varied applications.

arXiv:2102.13117•Physical Review Letters•May 19, 2021•18 citations

Tunable Geometries in Sparse Clifford Circuits

Tomohiro Hashizume, Sridevi Kuriyattil, Andrew J. Daley +1 more

We investigate the emergence of different effective geometries in stochastic Clifford circuits with sparse coupling. By changing the probability distribution for choosing two-site gates as a function of distance, we generate sparse interactions that either decay or grow with distance as a function of a single tunable parameter. Tuning this parameter reveals three distinct regimes of geometry for the spreading of correlations and growth of entanglement in the system. We observe linear geometry for short-range interactions, treelike geometry on a sparse coupling graph for long-range interactions, and an intermediate fast scrambling regime at the crossover point between the linear and treelike geometries. This transition in geometry is revealed in calculations of the subsystem entanglement entropy and tripartite mutual information. We also study emergent lightcones that govern these effective geometries by teleporting a single qubit of information from an input qubit to an output qubit. These tools help to analyze distinct geometries arising in dynamics and correlation spreading in quantum many-body systems.

arXiv:2202.11750•Symmetry•Mar 24, 2022•4 citations

Tuning between collective dynamics and scrambling through initial-state symmetry alignment in long-range spin models

Sridevi Kuriyattil, Johannes Kombe, Andrew J. Daley +1 more

Long-range interactions in many-body quantum systems give rise to a wide range of dynamical phenomena, from collective dynamics well described by integrable mean-field models with symmetric all-to-all couplings, to fast scrambling of quantum information from disordered long-range interactions. Here, we investigate scenarios in which both regimes emerge within a single deterministic, translation-invariant XY spin model with long-range couplings. We consider a sparse powers-of-two (PWR2) graph, where each spin interacts with a logarithmic number of neighbors, and a power-law-decaying model. By altering the initial state via local perturbations on a completely symmetric state, we show that the dynamics changes from collective to scrambling as witnessed by bipartite and multipartite entanglement measures. We characterize this collective-to-scrambling crossover using Lyapunov exponents in the semiclassical regime, and show that the spectral properties of the coupling graph adjacency matrix provide a very efficient tool to predict the onset of fast scrambling. Our results offer a unified framework for controlling the switch between collective and scrambling dynamics in a setup accessible in experiments with neutral atoms in cavities or in tweezer arrays.

quant-pharXiv:2610.28462•Oct 21, 2026•0 citations

Fast-Scrambling and Operator Confinement Using an Auxiliary Qubit

Szabo, Joseph, Nandini Trivedi

We introduce a minimal model for realizing a fast-to-slow scrambling transition mediated by an auxiliary central qubit (c-qubit). The c-qubit is coupled to a spin-$1/2$ Ising model with local Ising interactions and tunable c-qubit-spin coupling. Each spin becomes next-nearest neighbor to all others through the c-qubit, which mediates effective all-to-all interactions. As the interaction with the c-spin increases, we find a surprising transition from super-ballistic scrambling and information growth to continuously restricted sub-ballistic entanglement and operator growth. This slow growth occurs on intermediate timescales that extend exponentially with increasing coupling and system size, indicative of logarithmic entanglement growth. We find that in the slow-scrambling regime, the c-qubit Ising interaction allows commuting operators to grow support on all sites rapidly, while operators orthogonal to the interaction become echoed out. This projects local operators to lie in a restricted subspace and prevents extensive operator entanglement growth. We provide exact dynamics of small systems working with non-equilibrium, effective infinite temperature states, and additionally contribute analytic early-time expansions that support the observed rapid scrambling to quantum Zeno-like crossover. Tracing out the central qubit provides a unique translation from the full, closed unitary dynamics to a simple open system construction consisting of a typical spin-chain with hidden qubit degree of freedom.

arXiv:2301.02091•Jan 5, 2023•0 citations

Information scrambling and the correspondence of entanglement dynamics and operator dynamics in systems with nonlocal interactions

Darvin Wanisch, Juan Diego Arias Espinoza, S. Fritzsche

How fast quantum information scrambles such that it becomes inaccessible by local probes turns out to be central to various fields. Motivated by recent works on spin systems with nonlocal interactions, we study information scrambling in different variants of the Ising model. Our work reveals that nonlocal interactions can induce operator dynamics not precisely captured by out-of-time-order correlators (OTOCs). In particular, the operator size exhibits a slowdown in systems with generic power-law interactions despite a highly nonlinear light cone. A recently proposed microscopic model for fast scrambling does not show this slowdown, which uncovers a distinct analogy between a local operator under unitary evolution and the entanglement entropy following a quantum quench. Our work gives new insights on scrambling properties of systems in reach of current quantum simulation platforms and complements results on possibly observing features of quantum gravity in the laboratory.

arXiv:2209.09065•Physical review. B./Physical review. B•May 12, 2023•8 citations
We propose an experimentally realizable quantum spin model that exhibits fast scrambling, based on nonlocal interactions that couple sites whose separation is a power of 2. By controlling the relative strengths of deterministic, nonrandom couplings, we can continuously tune from the linear geometry of a nearest-neighbor spin chain to an ultrametric geometry in which the effective distance between spins is governed by their positions on a tree graph. The transition in geometry can be observed in quench dynamics, and is furthermore manifest in calculations of the entanglement entropy. Between the linear and treelike regimes, we find a peak in entanglement and exponentially fast spreading of quantum information across the system. Our proposed implementation, harnessing photon-mediated interactions among cold atoms in an optical cavity, offers a test case for experimentally observing the emergent geometry of a quantum many-body system.
Nonlocal light-mediated interactions between cold atoms coupled to the mode of an optical cavity present unique prospects for simulating the quantum dynamics of strongly-interacting many-body systems. In a recent publication, we introduced a tunable, nonlocal sparse spin network that can be engineered in near-term single-mode cavity QED platforms.1 In this companion paper, we study this spin network in detail and pedagogically review its basic dynamical properties, providing theoretical details and calculations that expand on the statements made in our original publication. We show that the network exhibits two distinct notions of emergent geometry - linear and treelike - that can be accessed using a single tunable parameter. In either of these two extreme limits, we find a succinct description of the resulting dynamics in terms of two distinct metrics on the network, encoding a notion of either linear or treelike distance between spins. We also show that the network can be mapped in these two extreme limits onto exactly solvable models: a linear Heisenberg spin chain in one limit, and a Dyson hierarchical model in the other. These observations highlight the essential role played by the geometry of the interaction structure in determining a system's dynamics, and raise prospects for novel studies of nonlocal and highly chaotic quantum dynamics in near-term experiments.
Fast scramblers are dynamical quantum systems that produce many-body entanglement on a timescale that grows logarithmically with the system size N. We propose and investigate a family of deterministic, fast scrambling quantum circuits realizable in near-term experiments with arrays of neutral atoms. We show that three experimental tools-nearest-neighbor Rydberg interactions, global single-qubit rotations, and shuffling operations facilitated by an auxiliary tweezer array-are sufficient to generate nonlocal interaction graphs capable of scrambling quantum information using only O(logN) parallel applications of nearest-neighbor gates. These tools enable direct experimental access to fast scrambling dynamics in a highly controlled and programmable way and can be harnessed to produce highly entangled states with varied applications.
We investigate the emergence of different effective geometries in stochastic Clifford circuits with sparse coupling. By changing the probability distribution for choosing two-site gates as a function of distance, we generate sparse interactions that either decay or grow with distance as a function of a single tunable parameter. Tuning this parameter reveals three distinct regimes of geometry for the spreading of correlations and growth of entanglement in the system. We observe linear geometry for short-range interactions, treelike geometry on a sparse coupling graph for long-range interactions, and an intermediate fast scrambling regime at the crossover point between the linear and treelike geometries. This transition in geometry is revealed in calculations of the subsystem entanglement entropy and tripartite mutual information. We also study emergent lightcones that govern these effective geometries by teleporting a single qubit of information from an input qubit to an output qubit. These tools help to analyze distinct geometries arising in dynamics and correlation spreading in quantum many-body systems.
Long-range interactions in many-body quantum systems give rise to a wide range of dynamical phenomena, from collective dynamics well described by integrable mean-field models with symmetric all-to-all couplings, to fast scrambling of quantum information from disordered long-range interactions. Here, we investigate scenarios in which both regimes emerge within a single deterministic, translation-invariant XY spin model with long-range couplings. We consider a sparse powers-of-two (PWR2) graph, where each spin interacts with a logarithmic number of neighbors, and a power-law-decaying model. By altering the initial state via local perturbations on a completely symmetric state, we show that the dynamics changes from collective to scrambling as witnessed by bipartite and multipartite entanglement measures. We characterize this collective-to-scrambling crossover using Lyapunov exponents in the semiclassical regime, and show that the spectral properties of the coupling graph adjacency matrix provide a very efficient tool to predict the onset of fast scrambling. Our results offer a unified framework for controlling the switch between collective and scrambling dynamics in a setup accessible in experiments with neutral atoms in cavities or in tweezer arrays.
We introduce a minimal model for realizing a fast-to-slow scrambling transition mediated by an auxiliary central qubit (c-qubit). The c-qubit is coupled to a spin-1/21/21/2 Ising model with local Ising interactions and tunable c-qubit-spin coupling. Each spin becomes next-nearest neighbor to all others through the c-qubit, which mediates effective all-to-all interactions. As the interaction with the c-spin increases, we find a surprising transition from super-ballistic scrambling and information growth to continuously restricted sub-ballistic entanglement and operator growth. This slow growth occurs on intermediate timescales that extend exponentially with increasing coupling and system size, indicative of logarithmic entanglement growth. We find that in the slow-scrambling regime, the c-qubit Ising interaction allows commuting operators to grow support on all sites rapidly, while operators orthogonal to the interaction become echoed out. This projects local operators to lie in a restricted subspace and prevents extensive operator entanglement growth. We provide exact dynamics of small systems working with non-equilibrium, effective infinite temperature states, and additionally contribute analytic early-time expansions that support the observed rapid scrambling to quantum Zeno-like crossover. Tracing out the central qubit provides a unique translation from the full, closed unitary dynamics to a simple open system construction consisting of a typical spin-chain with hidden qubit degree of freedom.
How fast quantum information scrambles such that it becomes inaccessible by local probes turns out to be central to various fields. Motivated by recent works on spin systems with nonlocal interactions, we study information scrambling in different variants of the Ising model. Our work reveals that nonlocal interactions can induce operator dynamics not precisely captured by out-of-time-order correlators (OTOCs). In particular, the operator size exhibits a slowdown in systems with generic power-law interactions despite a highly nonlinear light cone. A recently proposed microscopic model for fast scrambling does not show this slowdown, which uncovers a distinct analogy between a local operator under unitary evolution and the entanglement entropy following a quantum quench. Our work gives new insights on scrambling properties of systems in reach of current quantum simulation platforms and complements results on possibly observing features of quantum gravity in the laboratory.