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A discrete model of Lorentzian quantum gravity is proposed. The theory is completely background free, containing no reference to absolute space, time, or simultaneity. The states at one slice of time are networks in which each vertex is…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Aron C. Wall

Quantum metrology explores quantum effects to improve the measurement accuracy of some physical quantities beyond the classical limit. However, due to the interaction between the system and the environment, the decoherence can significantly…

Quantum Physics · Physics 2024-05-07 Cheng-Ge Liu , Cong-Wei Lu , Na-Na Zhang , Qing Ai

The metric underlying the mixed state geometric phase in unitary and nonunitary evolution [Phys. Rev. Lett. {\bf 85}, 2845 (2000); Phys. Rev. Lett. {\bf 93}, 080405 (2004)] is delineated. An explicit form for the line element is derived and…

Quantum Physics · Physics 2020-03-25 Erik Sjöqvist

We cast observable measure of quantum coherence or asymmetry as a resource to control the quantum speed limit (QSL) for unitary evolutions. For non-unitary evolutions, QSL depends on that of the state of the system and environment together.…

Quantum Physics · Physics 2016-02-17 Debasis Mondal , Chandan Datta , Sk Sazim

We study and compare the time evolutions of concurrence and quantum discord in a driven system of two interacting qubits prepared in a generic Werner state. The~corresponding quantum dynamics is exactly treated and manifests the appearance…

Quantum Physics · Physics 2020-10-09 Iulia Ghiu , Roberto Grimaudo , Tatiana Mihaescu , Aurelian Isar , Antonino Messina

The circuit complexity of time-evolved pure quantum states grows linearly in time for an exponentially long time. This behavior has been proven in certain models, is conjectured to hold for generic quantum many-body systems, and is believed…

High Energy Physics - Theory · Physics 2025-10-22 Yale Fan , Nicholas Hunter-Jones , Andreas Karch , Shivan Mittal

We explore further the suggestion to describe a pre- and post-selected system by a two-state, which is determined by two conditions. Starting with a formal definition of a two-state Hilbert space and basic operations, we systematically…

Quantum Physics · Physics 2009-10-28 B. Reznik , Y. Aharonov

The quantum coherence of a multipartite system is investigated when some of the parties are moving with uniform acceleration and the analysis is carried out using the single mode approximation. Due to acceleration the quantum coherence is…

Measurements transfer information about a system to the apparatus, and then further on -- to observers and (often inadvertently) to the environment. I show that even imperfect copying essential in such situations restricts possible…

Quantum Physics · Physics 2009-11-13 Wojciech Hubert Zurek

Quantum metrology exploits quantum mechanical effects to increase the precision of measurements of physical quantities. A wide variety of applications are currently being developed for scientific and technological purposes, however, most…

Quantum Physics · Physics 2026-02-16 B. J. Alexander , Ş. K. Özdemir , M. S. Tame

This work is originally a Cambridge Part III essay paper. Quantum complexity arises as an alternative measure to the Fubini metric between two quantum states. Given two states and a set of allowed gates, it is defined as the least complex…

Quantum Physics · Physics 2021-04-13 Andrea Russo

Studies have shown that quantum states reside in a Hilbert space bundle. When a quantum system depends on continuous external parameters, these parameters define additional dimensions in the base space of the bundle. While much of the…

Quantum Physics · Physics 2025-07-10 Chia-Yi Ju , Szu-Ming Chen

We explore the measurement problem in the entropic dynamics approach to quantum theory. The dual modes of quantum evolution---either continuous unitary evolution or abrupt wave function collapse during measurement---are unified by virtue of…

Quantum Physics · Physics 2015-05-30 David T. Johnson , Ariel Caticha

A collapse-free version of quantum theory is examined to systematically study the role of the projection postulate. This foil theory assumes "passive" measurements that do not update quantum states although measurement outcomes still occur…

Quantum Physics · Physics 2025-08-27 Vincenzo Fiorentino , Stefan Weigert

Dynamical quantum phase transitions (DQPTs) occur at times when a quantum state exhibits a nonanalytic change in its return probability. This can be viewed as the probability of collapsing the evolved state to the initial state by quantum…

Quantum Physics · Physics 2026-05-18 Guan-Hua Chen , Guo-Yi Zhu

We investigate the role of a statistical complexity measure to assign equilibration in isolated quantum systems. While unitary dynamics preserve global purity, expectation values of observables often exhibit equilibration-like behavior,…

Quantum Physics · Physics 2025-08-14 Marcos G. Alpino , Tiago Debarba , Reinaldo O. Vianna , André T. Cesário

We report the results of an experiment that searches for causal non-linear state-dependent terms in quantum field theory. Our approach correlates a binary macroscopic classical voltage with the outcome of a projective measurement of a…

We propose a new model for a measurement of a characteristic of a microscopic quantum state by a large system that selects stochastically the different eigenstates with appropriate quantum weights. Unlike previous works which formulate a…

Quantum Physics · Physics 2009-01-24 Fariel Shafee

The overlap measurement scheme accomplishes to evaluate the overlap of two input quantum states by only measuring an introduced auxiliary qubit, irrespective of the complexity of the two input states. We find a counterintuitive phenomenon…

Quantum Physics · Physics 2015-06-12 Chang-shui Yu , Jun Zhang , Heng Fan

Quantum entanglement is a foundational resource in quantum information science, underpinning applications across physics. However, detecting and quantifying entanglement remains a significant challenge. In this article, we introduce a…