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Spread complexity uses the distribution of support of a time-evolving state in the Krylov basis to quantify dispersal across accessible dimensions of a Hilbert space. Here, we describe how variations in initial conditions, the Hamiltonian,…

High Energy Physics - Theory · Physics 2025-11-19 Vijay Balasubramanian , Pawel Caputa , Joan Simón

We show that the characteristic function of the probability distribution associated with the change of an observable in a two-point measurement protocol with a perturbation can be written as an auto-correlation function between an initial…

Quantum Physics · Physics 2023-11-15 Ankit Gill , Kunal Pal , Kuntal Pal , Tapobrata Sarkar

We investigate quantum work statistics within the standard two-point measurement (TPM) scheme in continuously monitored quantum systems, including the effects of generalized unitary evolution, possibly controlled by quantum circuit models,…

Quantum Physics · Physics 2026-01-22 Manali Malakar , Alessandro Silva

The problem of the time of arrival of a quantum system in a specified state is considered in the framework of the repeated measurement protocol and in particular the limit of continuous measurements is discussed. It is shown that for a…

Quantum Physics · Physics 2021-04-07 Varun Dubey , Cedric Bernardin , Abhishek Dhar

We relate the probability distribution of the work done on a statistical system under a sudden quench to the Lanczos coefficients corresponding to evolution under the post-quench Hamiltonian. Using the general relation between the moments…

Quantum Physics · Physics 2023-09-19 Kuntal Pal , Kunal Pal , Ankit Gill , Tapobrata Sarkar

Complexity plays a very important part in quantum computing and simulation where it acts as a measure of the minimal number of gates that are required to implement a unitary circuit. We study the lower bound of the complexity [Eisert, Phys.…

Quantum Physics · Physics 2023-08-10 S. Aravinda , Ranjan Modak

We present a framework for investigating wave function spreading in $\mathcal{PT}$-symmetric quantum systems using spread complexity and spread entropy. We consider a tight-binding chain with complex on-site potentials at the boundary…

High Energy Physics - Theory · Physics 2024-06-07 Aranya Bhattacharya , Rathindra Nath Das , Bidyut Dey , Johanna Erdmenger

We consider the statistics of the results of a measurement of the spreading operator in the Krylov basis generated by the Hamiltonian of a quantum system starting from a specified initial pure state. We first obtain the probability…

Quantum Physics · Physics 2025-09-11 Yichao Fu , Keun-Young Kim , Kunal Pal , Kuntal Pal

In this series of works, we study exactly solvable non-unitary time evolutions in one-dimensional quantum critical systems ranging from quantum quenches to time-dependent drivings. In this part I, we are motivated by the recent works of…

Statistical Mechanics · Physics 2024-10-30 Xueda Wen

We discuss the short-time perturbative expansion of the linear entropy for finite-dimensional quantum systems whose dynamics can be effectively described by a non-Hermitian Hamiltonian. We derive a timescale for the degree of mixedness for…

Quantum Physics · Physics 2023-02-07 Diego Paiva Pires , Tommaso Macrì

We investigate measurement-induced localization in a continuously monitored one-dimensional Aubry--Andr\'e--Harper model, focusing on the quantum Zeno regime in which the measurements dominate coherent dynamics. The presence of a…

Statistical Mechanics · Physics 2026-05-15 Pinaki Singha , Nilanjan Roy , Marcin Szyniszewski , Auditya Sharma

Non-Hermitian quantum many-body systems are attracting widespread interest for their exotic properties, including unconventional quantum criticality and topology. Here we study how quantum information and correlations spread under a quantum…

Statistical Mechanics · Physics 2023-01-18 Xhek Turkeshi , Marco Schiró

For one-dimensional non-interacting complex fermions, we compute numerically the probability distribution of the change in the entanglement entropy (EE) after saturation, resulting from a single measurement of the occupation number by using…

Quantum Physics · Physics 2026-03-03 Bo Fan , Can Yin , Antonio M. García-García

In this work we generalize the concept of modular spread complexity to the cases where the reduced density matrix is non-Hermitian. This notion of complexity and associated Lanczos coefficients contain richer information than the…

High Energy Physics - Theory · Physics 2024-10-08 Aneek Jana , Maitri Ganguli

We explore the nonunitary dynamics of $(2+1)$-dimensional free fermions and show that the obtained steady state is critical regardless the strength of the nonunitary evolution. Numerical results indicate that the entanglement entropy has a…

Statistical Mechanics · Physics 2021-05-13 Qicheng Tang , Xiao Chen , W. Zhu

Measurement is one of the most counter-intuitive aspects of quantum physics. Frequent measurements of a quantum system lead to quantum Zeno dynamics where time evolution becomes confined to a subspace defined by the projections. However,…

Quantum Physics · Physics 2016-08-03 Wojciech Kozlowski , Santiago F. Caballero-Benitez , Igor B. Mekhov

We study a one-dimensional lattice system of free fermions subjected to a generalized measurement process: the system exchanges particles with its environment, but each fermion leaving or entering the system is counted. In contrast to the…

Quantum Physics · Physics 2025-07-29 Elias Starchl , Mark H. Fischer , Lukas M. Sieberer

In order to resolve the measurement problem of Quantum Mechanics, non-unitary time evolution has been derived from the unitarity of standard quantum formalism. New wave functions of free and non-free quantum systems follow from Schroedinger…

Quantum Physics · Physics 2007-05-23 Pradip Kumar Chatterjee

Recently, the concept of spread complexity, Krylov complexity for states, has been introduced as a measure of the complexity and chaoticity of quantum systems. In this paper, we study the spread complexity of the thermofield double state…

High Energy Physics - Theory · Physics 2024-05-27 Kyoung-Bum Huh , Hyun-Sik Jeong , Juan F. Pedraza

We consider a free fermionic chain with monitoring of the particle density on a single site of the chain and study the entanglement dynamics of quantum jump trajectories. We show that the entanglement entropy grows in time towards a…

Quantum Physics · Physics 2025-01-20 Giovanni Di Fresco , Youenn Le Gal , Davide Valenti , Marco Schirò , Angelo Carollo
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