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Understanding the structure of multi-qubit quantum states is essential for both quantum information research and education, yet intuitive visualization beyond the single-qubit Bloch sphere remains challenging. In this work, we propose a…

Quantum Physics · Physics 2026-03-11 Satoru Shoji

Krylov subspace methods in quantum dynamics identify the minimal subspace in which a process unfolds. To date, their use is restricted to time evolutions governed by time-independent generators. We introduce a generalization valid for…

Quantum Physics · Physics 2025-01-27 Kazutaka Takahashi , Adolfo del Campo

As time passes, once simple quantum states tend to become more complex. For strongly coupled k-local Hamiltonians, this growth of computational complexity has been conjectured to follow a distinctive and universal pattern. In this paper we…

High Energy Physics - Theory · Physics 2017-02-28 Adam R. Brown , Leonard Susskind , Ying Zhao

We investigate Krylov complexity in open quantum systems using Lindblad master equations for bosonic bath models, with particular emphasis on the Caldeira--Leggett model. Krylov complexity is computed from the moments of the two-point…

High Energy Physics - Theory · Physics 2026-04-22 Arpan Bhattacharyya , Sayed Gool , S. Shajidul Haque

The emergence of cosmic structure is commonly considered one of the most complex phenomena in Nature. However, this complexity has never been defined nor measured in a quantitative and objective way. In this work we propose a method to…

Cosmology and Nongalactic Astrophysics · Physics 2016-11-29 Franco Vazza

In this article, we investigate various physical implications of quantum circuit complexity using squeezed state formalism of Primordial Gravitational Waves (PGW). Recently quantum information theoretic concepts, such as entanglement…

General Relativity and Quantum Cosmology · Physics 2023-03-07 Kiran Adhikari , Sayantan Choudhury , Hardey N. Pandya , Rohan Srivastava

Kolmogorov complexity is a measure of the information contained in a binary string. We investigate here the notion of quantum Kolmogorov complexity, a measure of the information required to describe a quantum state. We show that for any…

Quantum Physics · Physics 2007-05-23 C. Mora , H. Briegel , B. Kraus

We investigate operator growth in quantum systems with two-dimensional Schr\"odinger group symmetry by studying the Krylov complexity. While feasible for semisimple Lie algebras, cases such as the Schr\"odinger algebra which is…

Quantum Physics · Physics 2024-04-10 Dimitrios Patramanis , Watse Sybesma

Information geometry provides a tool to systematically investigate parameter sensitivity of the state of a system. If a physical system is described by a linear combination of eigenstates of a complex (that is, non-Hermitian) Hamiltonian,…

Quantum Physics · Physics 2013-08-26 Dorje C. Brody , Eva-Maria Graefe

We propose a new diagnostic for quantum chaos. We show that time evolution of complexity for a particular type of target state can provide equivalent information about the classical Lyapunov exponent and scrambling time as out-of-time-order…

High Energy Physics - Theory · Physics 2020-02-05 Tibra Ali , Arpan Bhattacharyya , S. Shajidul Haque , Eugene H. Kim , Nathan Moynihan , Jeff Murugan

Quantum computational complexity estimates the difficulty of constructing quantum states from elementary operations, a problem of prime importance for quantum computation. Surprisingly, this quantity can also serve to study a completely…

High Energy Physics - Theory · Physics 2022-03-02 Shira Chapman , Giuseppe Policastro

The complex geometry underlying the Schr\"odinger dynamics of coherent states for non-Hermitian Hamiltonians is investigated. In particular two seemingly contradictory approaches are compared: (i) a complex WKB formalism, for which the…

Mathematical Physics · Physics 2012-07-12 Eva-Maria Graefe , Roman Schubert

We compute the Krylov Complexity of a light operator $\mathcal{O}_L$ in an eigenstate of a $2d$ CFT at large central charge $c$. The eigenstate corresponds to a primary operator $\mathcal{O}_H$ under the state-operator correspondence. We…

High Energy Physics - Theory · Physics 2023-10-18 Arnab Kundu , Vinay Malvimat , Ritam Sinha

This work provides a nonasymptotic error analysis of quantum Krylov algorithms based on real-time evolutions, subject to generic errors in the outputs of the quantum circuits. We prove upper and lower bounds on the resulting ground state…

Quantum Physics · Physics 2024-09-04 William Kirby

We present a novel inequality on the purity of a bipartite state depending solely on the difference of the local Bloch vector lengths. For two qubits this inequality is tight for all marginal states and so extends the previously known…

Quantum Physics · Physics 2024-01-23 Simon Morelli , Christopher Eltschka , Marcus Huber , Jens Siewert

We study quantum dynamics generated by time-dependent Hamiltonians in Krylov space, the minimal subspace in which the evolution takes place. We establish a direct link between dynamics in the time-dependent Krylov subspace and the…

Quantum Physics · Physics 2026-05-18 András Grabarits , E. Medina-Guerra , Adolfo del Campo

We study generalized indicators of sensitivity to initial conditions and orbit complexity in topological dynamical systems. The orbit complexity is a measure of the asymptotic behavior of the information that is necessary to describe the…

Dynamical Systems · Mathematics 2016-09-07 Stefano Galatolo

Strongly interacting quantum many-body systems are expected to thermalize, however, some evade thermalization due to symmetries. Quantum synchronization provides one such example of ergodicity breaking, but previous studies have focused on…

Disordered Systems and Neural Networks · Physics 2026-02-13 Nicolas Loizeau , Berislav Buča

We studied geometric quantum speed limits (QSL) of a qubit subject to decoherence in an ensemble of chloroform molecules in a Nuclear Magnetic Resonance experiment. The QSL is a fundamental lower bound on the evolution time for quantum…

Computational complexity is a new quantum information concept that may play an important role in holography and in understanding the physics of the black hole interior. We consider quantum computational complexity for $n$ qubits using…

High Energy Physics - Theory · Physics 2021-05-21 Roberto Auzzi , Stefano Baiguera , G. Bruno De Luca , Andrea Legramandi , Giuseppe Nardelli , Nicolò Zenoni