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We study the statistical properties of the spread complexity in the Krylov space of quantum systems driven across a quantum phase transition. Using the diabatic Magnus expansion, we map the evolution to an effective one-dimensional hopping…

Quantum Physics · Physics 2026-05-26 András Grabarits , Adolfo del Campo

In this paper, we investigate the dynamics of a non-Hermitian SSH model that arises out of the no-click limit of a monitored SSH model in the Krylov space. We find that the saturation timescale of the complexity associated with the spread…

Quantum Physics · Physics 2025-07-22 Nilachal Chakrabarti , Neha Nirbhan , Arpan Bhattacharyya

Considering the large-$q$ expansion of the Sachdev-Ye-Kitaev (SYK) model in the two-stage limit, we compute the Lanczos coefficients, Krylov complexity, and the higher Krylov cumulants in subleading order, along with the $t/q$ effects. The…

High Energy Physics - Theory · Physics 2023-08-21 Budhaditya Bhattacharjee , Pratik Nandy , Tanay Pathak

In this work, we explore in detail, the time evolution of Krylov complexity. We demonstrate, through analytical computations, that in finite many-body systems, while ramp and plateau are two generic features of Krylov complexity, the manner…

High Energy Physics - Theory · Physics 2025-08-06 Mohsen Alishahiha , Souvik Banerjee , Mohammad Javad Vasli

We point out an interesting connection between the mathematical framework of the Krylov basis, which is used to quantify quantum complexity, and the entanglement entropy in high-energy QCD. In particular, we observe that the cascade…

High Energy Physics - Phenomenology · Physics 2024-10-25 Pawel Caputa , Krzysztof Kutak

Krylov complexity has emerged as a new probe of operator growth in a wide range of non-equilibrium quantum dynamics. However, a fundamental issue remains in such studies: the definition of the distance between basis states in Krylov space…

Quantum Physics · Physics 2023-03-14 Chenwei Lv , Ren Zhang , Qi Zhou

We characterize the Many-Body Localization (MBL) phase transition using the dynamics of spread complexity and inverse participation ratio in the Krylov space starting from different initial states. Our analysis of the disordered Heisenberg…

Disordered Systems and Neural Networks · Physics 2024-09-05 Maitri Ganguli , Aneek Jana

Commonly, the notion of "quantum chaos'' refers to the fast scrambling of information throughout complex quantum systems undergoing unitary evolution. Motivated by the Krylov complexity and the operator growth hypothesis, we demonstrate…

Quantum Physics · Physics 2024-09-19 Eoin Carolan , Anthony Kiely , Steve Campbell , Sebastian Deffner

Krylov complexity is a novel approach to study how an operator spreads over a specific basis. Recently, it has been stated that this quantity has a long-time saturation that depends on the amount of chaos in the system. Since this quantity…

Quantum Physics · Physics 2023-03-08 Bernardo L. Español , Diego A. Wisniacki

We propose a measure of quantum state complexity defined by minimizing the spread of the wave-function over all choices of basis. Our measure is controlled by the "survival amplitude" for a state to remain unchanged, and can be efficiently…

High Energy Physics - Theory · Physics 2022-09-14 Vijay Balasubramanian , Pawel Caputa , Javier Magan , Qingyue Wu

Krylov complexity is a measure of operator growth in quantum systems, based on the number of orthogonal basis vectors needed to approximate the time evolution of an operator. In this paper, we study the Krylov complexity of a…

High Energy Physics - Theory · Physics 2023-12-27 Cameron Beetar , Nitin Gupta , S. Shajidul Haque , Jeff Murugan , Hendrik J R Van Zyl

Krylov complexity and Nielsen complexity are successful approaches to quantifying quantum evolution complexity that have been actively pursued without much contact between the two lines of research. The two quantities are motivated by…

Quantum Physics · Physics 2024-04-19 Ben Craps , Oleg Evnin , Gabriele Pascuzzi

Heisenberg time evolution under a chaotic many-body Hamiltonian $H$ transforms an initially simple operator into an increasingly complex one, as it spreads over Hilbert space. Krylov complexity, or `K-complexity', quantifies this growth…

High Energy Physics - Theory · Physics 2021-06-30 E. Rabinovici , A. Sánchez-Garrido , R. Shir , J. Sonner

We introduce and review a new complexity measure, called `Krylov complexity', which takes its origins in the field of quantum-chaotic dynamics, serving as a canonical measure of operator growth and spreading. Krylov complexity, underpinned…

High Energy Physics - Theory · Physics 2025-07-10 Eliezer Rabinovici , Adrián Sánchez-Garrido , Ruth Shir , Julian Sonner

Weak ergodicity breaking, particularly through quantum many-body scars (QMBS), has become a significant focus in many-body physics. Krylov state complexity quantifies the spread of quantum states within the Krylov basis and serves as a…

Strongly Correlated Electrons · Physics 2025-04-08 Qingmin Hu , Wen-Yi Zhang , Yunguang Han , Wen-Long You

Long-range interacting spin systems are ubiquitous in physics and exhibit a variety of ground state disorder-to-order phase transitions. We consider a prototype of infinite-range interacting models known as the Lipkin-Meshkov-Glick (LMG)…

Quantum Gases · Physics 2020-07-29 Paraj Titum , Mohammad F. Maghrebi

We study how a machine based on deep learning algorithms learns Krylov spread complexity in quantum systems with N x N random Hamiltonians drawn from the Gaussian unitary ensemble. Using thermofield double states as initial conditions, we…

Quantum Physics · Physics 2025-11-19 Dongsu Bak , Su-Hyeong Kim , Sangnam Park , Jeong-Pil Song

Krylov complexity has recently emerged as a useful probe of operator growth and quantum dynamics in many-body systems and holographic dualities. In this paper we study its behavior in the Veneziano--Wosiek model, a supersymmetric matrix…

High Energy Physics - Theory · Physics 2026-03-24 Eleonora Alfinito , Matteo Beccaria

Krylov complexity has been proposed as a diagnostic of chaos in non-integrable lattice and quantum mechanical systems, and if the system is chaotic, Krylov complexity grows exponentially with time. However, when Krylov complexity is applied…

High Energy Physics - Theory · Physics 2024-01-10 Takanori Anegawa , Norihiro Iizuka , Mitsuhiro Nishida

Krylov complexity is an attractive measure for the rate at which quantum operators spread in the space of all possible operators under dynamical evolution. One expects that its late-time plateau would distinguish between integrable and…

Quantum Physics · Physics 2025-02-05 Ben Craps , Oleg Evnin , Gabriele Pascuzzi