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This article surveys quantum computational complexity, with a focus on three fundamental notions: polynomial-time quantum computations, the efficient verification of quantum proofs, and quantum interactive proof systems. Properties of…

Quantum Physics · Physics 2008-04-23 John Watrous

This paper explores the problem of quantum measurement complexity. In computability theory, the complexity of a problem is determined by how long it takes an effective algorithm to solve it. This complexity may be compared to the difficulty…

Quantum Physics · Physics 2014-10-27 Subhash Kak

In our thesis, we try to shed more light onto the complexity of quantum complexity classes by refining the related part of the hierarchy. First, we review the basic concepts of quantum computing in general. Then, inspired by BQP, we define…

Computational Complexity · Computer Science 2007-05-23 Tereza Tusarova

The theory of quantum gravity is aimed to fuse general relativity with quantum theory into a more fundamental framework. The space of quantum gravity provides both the non-fixed causality of general relativity and the quantum uncertainty of…

Quantum Physics · Physics 2020-03-12 Laszlo Gyongyosi , Sandor Imre

This is an introduction to the group field theory approach to quantum gravity, with emphasis on motivations and basic formalism, more than on recent results; we elaborate on the various ingredients, both conceptual and formal, of the…

General Relativity and Quantum Cosmology · Physics 2012-03-27 Daniele Oriti

Complexity is a multi-faceted phenomenon, involving a variety of features including disorder, nonlinearity, and self-organisation. We use a recently developed rigorous framework for complexity to understand measures of complexity. We…

Adaptation and Self-Organizing Systems · Physics 2020-09-22 Karoline Wiesner , James Ladyman

In classical mechanics the complexity of a dynamical system is characterized by the rate of local exponential instability which effaces the memory of initial conditions and leads to practical irreversibility. In striking contrast, quantum…

Quantum Physics · Physics 2009-02-24 Giuliano Benenti , Giulio Casati

Recent years have seen significant activity on the problem of using data for the purpose of learning properties of quantum systems or of processing classical or quantum data via quantum computing. As in classical learning, quantum learning…

Quantum Physics · Physics 2024-04-17 Leonardo Banchi , Jason Luke Pereira , Sharu Theresa Jose , Osvaldo Simeone

The complexity of the quantum state of a multiparticle system and the maximum possible accuracy of its quantum description are connected by a relation similar to the coordinate-momentum uncertainty relation. The coefficient in this relation…

Quantum Physics · Physics 2021-10-01 Yuri I. Ozhigov

We investigate notions of complexity of states in continuous quantum-many body systems. We focus on Gaussian states which include ground states of free quantum field theories and their approximations encountered in the context of the…

High Energy Physics - Theory · Physics 2018-11-15 Shira Chapman , Michal P. Heller , Hugo Marrochio , Fernando Pastawski

In this paper, we analyze the circuit complexity for preparing ground states of quantum many-body systems. In particular, how this complexity grows as the ground state approaches a quantum phase transition. We discuss different definitions…

Quantum Physics · Physics 2023-11-08 Sebastián Roca-Jerat , Teresa Sancho-Lorente , Juan Román-Roche , David Zueco

State transformation problems such as compressing quantum information or breaking quantum commitments are fundamental quantum tasks. However, their computational difficulty cannot easily be characterized using traditional complexity theory,…

Quantum Physics · Physics 2025-07-30 John Bostanci , Yuval Efron , Tony Metger , Alexander Poremba , Luowen Qian , Henry Yuen

We discuss a classical complexity of finite-dimensional unitary transformations, which can been seen as a computable approximation of classical descriptional complexity of a unitary transformation acting on a set of qubits.

Quantum Physics · Physics 2023-04-03 Alexei Kaltchenko

This is an introduction to quantum gravity, aimed at a fairly general audience and concentrating on what have historically two main approaches to quantum gravity: the covariant and canonical programs (string theory is not covered). The…

General Relativity and Quantum Cosmology · Physics 2007-05-23 David Wallace

This paper defines a complexity between states in quantum field theory by introducing a Finsler structure based on ladder operators (the generalization of creation and annihilation operators). Two simple models are shown as examples to…

High Energy Physics - Theory · Physics 2018-03-09 Run-Qiu Yang

The problem of characterizing complexity of quantum dynamics - in particular of locally interacting chains of quantum particles - will be reviewed and discussed from several different perspectives: (i) stability of motion against external…

Quantum Physics · Physics 2009-11-13 Tomaz Prosen

We study the relation between quantum computational complexity and general relativity. The quantum computational complexity is proposed to be quantified by the shortest length of geodesic quantum curves. We examine the complexity/volume…

High Energy Physics - Theory · Physics 2018-03-14 Xian-Hui Ge , Bin Wang

In classical theory, the physical systems are elucidated through the concepts of particles and waves, which aim to describe the reality of the physical system with certainty. In this framework, particles are mathematically represented by…

Quantum Physics · Physics 2024-09-25 Mohammad Vahid Takook , Ali Mohammad-Djafari

This paper considers the realizability of quantum gates from the perspective of information complexity. Since the gate is a physical device that must be controlled classically, it is subject to random error. We define the complexity of gate…

Quantum Physics · Physics 2009-11-11 Subhash Kak

Nielsen's geometric approach offers a powerful framework for quantifying the complexity of unitary transformations. In this formulation, complexity is defined as the length of the minimal geodesic in a suitably constructed geometric space…

High Energy Physics - Theory · Physics 2025-12-18 Satyaki Chowdhury , Jakub Mielczarek