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It is conjectured that in the geometric formulation of quantum computing, one can study quantum complexity through classical entropy of statistical ensembles established non-relativistically in the group manifold of unitary operators. The…

High Energy Physics - Theory · Physics 2018-08-27 Ning Bao , Junyu Liu

The space of quantum states can be endowed with a metric structure using the second order derivatives of the relative entropy, giving rise to the so-called Kubo-Mori-Bogoliubov inner product. We explore its geometric properties on the…

Quantum Physics · Physics 2024-07-23 Harry J. D. Miller

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

We formulate the problem of determining the volume of the set of Gaussian physical states in the framework of information geometry. That is, by considering phase space probability distributions parametrized by the covariances and supplying…

Mathematical Physics · Physics 2017-01-13 Domenico Felice , Hà Quang Minh , Stefano Mancini

The popular qubit framework has dominated recent work on quantum kernel machine learning, with results characterising expressivity, learnability and generalisation. As yet, there is no comparative framework to understand these concepts for…

Quantum Physics · Physics 2024-12-18 Laura J. Henderson , Rishi Goel , Sally Shrapnel

We present a systematic perturbative construction of the most general metric operator (and positive-definite inner product) for quasi-Hermitian Hamiltonians of the standard form, H= p^2/2 + v(x), in one dimension. We show that this problem…

Quantum Physics · Physics 2009-11-11 Ali Mostafazadeh

Understanding the complexity of quantum many-body systems has been attracting much attention recently for its fundamental importance in characterizing complex quantum phases beyond the scope of quantum entanglement. Here, we investigate…

Quantum Physics · Physics 2025-07-31 Wei Xia , Yijia Zhou , Xingze Qiu , Xiaopeng Li

Bosonic two-mode squeezed states are paradigmatic entangled Gaussian states that have wide utility in quantum information and metrology. Here, we show that the basic structure of these states can be generalized to arbitrary bipartite…

Quantum Physics · Physics 2025-02-27 Mikhail Mamaev , Martin Koppenhöfer , Andrew Pocklington , Aashish A. Clerk

Continuous variable (CV) quantum computation offers an alternative to qubit-based computing by exploiting the infinite-dimensional Hilbert space of bosonic modes. Despite recent progress, superconducting platforms have yet to demonstrate a…

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

The quantum dynamics of a complex system can be efficiently described in Krylov space, the minimal subspace in which the dynamics unfolds. We apply the Krylov subspace method for Hamiltonian deformations, which provides a systematic way of…

Quantum Physics · Physics 2026-04-21 Kazutaka Takahashi , Pratik Nandy , Adolfo del Campo

We introduce a quantifier of phase-space complexity for discrete-variable (DV) quantum systems. Motivated by a recent framework developed for continuous-variable systems, we construct a complexity measure of quantum states based on the…

Quantum Physics · Physics 2026-03-05 Siting Tang , Shunlong Luo , Matteo G. A. Paris

In their seminal paper, Caves and Schumaker presented a new formalism for quantum optics, intended to serve as a building block for describing two-photon processes, in terms of new, generalized qudratures. The important, revolutionary…

Quantum Physics · Physics 2021-12-02 Leon Bello , Yoad Michael , Michael Rosenbluh , Eliahu Cohen , Avi Pe'er

The spectroscopic properties of an open large Bunimovich cavity are studied numerically in the framework of the effective Hamiltonian formalism. The cavity is opened by attaching leads to it in four different ways. In some cases,…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 E. N. Bulgakov , I. Rotter

In quantum information theory, a geometric approach, known as "quantum information geometry," has been considered as a powerful method. In this thesis, we give a computational geometric interpretation to the geometric structure of a quantum…

Quantum Physics · Physics 2008-03-24 Kimikazu Kato

The preparation of quantum many-body systems faces the difficulty that in a realistic scenario only few control parameters of the system may be accessible. In this context, an interesting connection between the energy fluctuations during…

Quantum Physics · Physics 2025-08-29 Maximilian Goll , Robert H. Jonsson

We derive some of the central equations governing quantum fluctuations in gravitational waves, making use of general relativity as a sensible effective quantum theory at large distances. We begin with a review of classical gravitational…

General Relativity and Quantum Cosmology · Physics 2023-03-06 Mark P. Hertzberg , Jacob A. Litterer

We study Nielsen complexity and Fubini-Study complexity for a class of exactly solvable one dimensional spin systems. Our examples include the transverse XY spin chain and its natural extensions, the quantum compass model with and without…

Statistical Mechanics · Physics 2021-08-25 Nitesh Jaiswal , Mamta Gautam , Tapobrata Sarkar

In this work, we investigate the impact of conserved charges on the dynamics of spread complexity of quantum states. Building on the notion of symmetry-resolved Krylov complexity [1], we extend the framework to general quantum states and…

High Energy Physics - Theory · Physics 2025-09-17 Pawel Caputa , Giuseppe Di Giulio , Tran Quang Loc

We develop a spectral-resolvent framework for computing the quantum Fisher information (QFI) using Krylov subspace methods, extending the notion of the Krylov distribution. By expressing the QFI as a resolvent moment of the superoperator…

Quantum Physics · Physics 2026-04-21 Mohsen Alishahiha , Fatemeh Tarighi Tabesh , Mohammad Javad Vasli