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We argue that complex systems science and the rules of quantum physics are intricately related. We discuss a range of quantum phenomena, such as cryptography, computation and quantum phases, and the rules responsible for their complexity.…

Quantum Physics · Physics 2011-10-25 Janet Anders , Karoline Wiesner

We establish a direct connection between spread complexity and quantum circuit complexity by demonstrating that spread complexity emerges as a limiting case of a circuit complexity framework built from two fundamental operations:…

High Energy Physics - Theory · Physics 2026-05-19 Cameron Beetar , Eric L Graef , Jeff Murugan , Horatiu Nastase , Hendrik J R Van Zyl

We introduce a notion of Kolmogorov complexity of unitary transformation, which can (roughly) be understood as the least possible amount of information required to fully describe and reconstruct a given finite unitary transformation. In the…

Quantum Physics · Physics 2022-01-20 Alexei Kaltchenko

Query complexity is a model of computation in which we have to compute a function $f(x_1, \ldots, x_N)$ of variables $x_i$ which can be accessed via queries. The complexity of an algorithm is measured by the number of queries that it makes.…

Quantum Physics · Physics 2017-12-19 Andris Ambainis

The physics of quantum gravity is discussed within the framework of topological quantum field theory. Some of the principles are illustrated with examples taken from theories in which space-time is three dimensional.

General Relativity and Quantum Cosmology · Physics 2009-10-28 John W. Barrett

Depth is a complexity measure for natural systems of the kind studied in statistical physics and is defined in terms of computational complexity. Depth quantifies the length of the shortest parallel computation required to construct a…

Popular Physics · Physics 2011-11-14 Jon Machta

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

Complexity in quantum physics measures how difficult a state can be reached from a reference state and more precisely it is the number of fundamental unitary gates we have to operate to transform the reference state to the state we are…

High Energy Physics - Theory · Physics 2020-06-05 Hao Geng

In the present paper we propose a new approach to quantum fields in terms of category algebras and states on categories. We define quantum fields and their states as category algebras and states on causal categories with partial involution…

Mathematical Physics · Physics 2021-12-14 Hayato Saigo

We apply the recently developed notion of complexity for field theory to a quantum quench through a critical point in 1+1 dimensions. We begin with a toy model consisting of a quantum harmonic oscillator, and show that complexity exhibits…

High Energy Physics - Theory · Physics 2019-03-06 Hugo A. Camargo , Pawel Caputa , Diptarka Das , Michal P. Heller , Ro Jefferson

Because the subject of relativistic quantum field theory (QFT) contains all of non-relativistic quantum mechanics, we expect quantum field computation to contain (non-relativistic) quantum computation. Although we do not yet have a quantum…

Quantum Physics · Physics 2007-05-23 A. C. Manoharan

Group field theories are a new type of field theories over group manifolds and a generalization of matrix models, that have recently attracted much interest in quantum gravity research. They represent a development of and a possible link…

High Energy Physics - Theory · Physics 2007-11-28 Daniele Oriti

I shall discuss some "conditions of possibility" of a quantum theory of gravity, stressing the need for solutions to some of fundamental problems confronting any attempt to apply some method of quantization to the field equations of general…

General Relativity and Quantum Cosmology · Physics 2007-05-23 John Stachel

This article is an introduction to quant-ph/0302092. We propose to quantify how "quantum" a set of quantum states is. The quantumness of a set is the worst-case difficulty of transmitting the states through a classical communication…

Quantum Physics · Physics 2007-05-23 Christopher A. Fuchs , Masahide Sasaki

While we have intuitive notions of structure and complexity, the formalization of this intuition is non-trivial. The statistical complexity is a popular candidate. It is based on the idea that the complexity of a process can be quantified…

Quantum Physics · Physics 2014-09-24 Ryan Tan , Daniel R. Terno , Jayne Thompson , Vlatko Vedral , Mile Gu

Generic open quantum dynamics can be described by two seemingly very distinct approaches: a top down approach by considering an (unknown) environment coupled to the system and affects the observed dynamics of the system; or a bottom up…

Quantum Physics · Physics 2022-03-31 Chu Guo

Quantum gravity (or quantum spacetime) is to unify general relativity and quantum mechanics into a single theoretical framework and presented as the most important open puzzle in fundamental physics. The development of a microscopic theory…

General Physics · Physics 2025-10-24 Su-Peng Kou

These lecture notes are an informal introduction to the theory of computational complexity and its links to quantum computing and statistical mechanics.

Statistical Mechanics · Physics 2009-09-25 Stephan Mertens

Effective field theories consistent with quantum gravity obey surprising finiteness constraints, appearing in several distinct but interconnected forms. In this work we develop a framework that unifies these observations by proposing that…

High Energy Physics - Theory · Physics 2026-02-11 Thomas W. Grimm , David Prieto , Mick van Vliet

Theoretical developments related to the gravitational interaction have questioned the notion of particle in quantum field theory (QFT). For instance, uniquely-defined particle states do not exist in general, in QFT on a curved spacetime.…

General Relativity and Quantum Cosmology · Physics 2013-05-07 Daniele Colosi , Carlo Rovelli