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We experimentally implement a machine-learning method for accurately identifying unknown pure quantum states. The method, called single-shot measurement learning, achieves the theoretical optimal accuracy for $\epsilon = O(N^{-1})$ in state…

Quantum Physics · Physics 2021-05-05 Sang Min Lee , Hee Su Park , Jinhyoung Lee , Jaewan Kim , Jeongho Bang

Whereas complementarity manifests itself via two incompatible observables, quantum contextuality can only be revealed via the joint measurements among at least three observables. By incorporating unsharp measurements and joint measurements…

Quantum Physics · Physics 2013-12-24 Sixia Yu , C. H. Oh

It is shown that an ideal measurement of a one-particle wave packet state of a relativistic quantum field in Minkowski spacetime enables superluminal signalling. The result holds for a measurement that takes place over an intervention…

Quantum Physics · Physics 2014-03-14 Dionigi M. T. Benincasa , Leron Borsten , Michel Buck , Fay Dowker

In the standard von Neumann interaction used in Quantum measurements, the chosen observable to which the environment (apparatus) entangles is exactly reproduced in the state of the environment, thereby decohering the quantum system in the…

Quantum Physics · Physics 2024-01-11 Adarsh S , P. N. Bala Subramanian , T. P. Sreeraj

The normalized state $\ket{\psi(t)}=c_1(t)\ket{1}+c_2(t)\ket{2}$ of a single two-level system performs oscillations under the influence of a resonant driving field. It is assumed that only one realization of this process is available. We…

Quantum Physics · Physics 2009-11-06 Juergen Audretsch , Thomas Konrad , Artur Scherer

This paper presents a framework for Quantum causal modeling based on the interpretation of causality as a relation between an observer's probability assignments to hypothetical or counterfactual experiments. The framework is based on the…

Quantum Physics · Physics 2020-01-15 Jacques Pienaar

We introduce observable quantities, borrowing from concepts of quantum information theory, for the characterization of quantum phase transitions in spin systems. These observables are uniquely defined in terms of single spin unitary…

Quantum Physics · Physics 2007-05-23 S. M. Giampaolo , F. Illuminati , S. De Siena

For classical field theories with probabilistic initial conditions the classical field observables are an idealization. Their arbitrarily precise values poorly reflect the characteristic uncertainty in the presence of substantial…

Quantum Physics · Physics 2026-03-06 Christof Wetterich

Quantum mechanical operators and quantum fields are interpreted as realizations of timespace manifolds. Such causal manifolds are parametrized by the classes of the positive unitary operations in all complex operations, i.e. by the…

High Energy Physics - Theory · Physics 2009-10-30 Heinrich Saller

This paper addresses the question whether a variant of a modal interpretation is conceivable that could accommodate property ascriptions associated with nonorthogonal resolutions of the unity and nonorthogonal families of relative states as…

Quantum Physics · Physics 2007-05-23 P. Busch

We probe the foundations of causal structure inference experimentally. The causal structure concerns which events influence other events. We probe whether causal structure can be determined without intervention in quantum systems.…

Quantum Physics · Physics 2024-11-12 Hongfeng Liu , Xiangjing Liu , Qian Chen , Yixian Qiu , Vlatko Vedral , Xinfang Nie , Oscar Dahlsten , Dawei Lu

Joint measurements of non-commuting observables are characterized by unavoidable measurement uncertainties that can be described in terms of the error statistics for input states with well-defined values for the target observables. However,…

Quantum Physics · Physics 2015-10-28 Shota Kino , Taiki Nii , Holger F. Hofmann

Hybrid evolution protocols, composed of unitary dynamics and repeated, weak or projective measurements, give rise to new, intriguing quantum phenomena, including entanglement phase transitions and unconventional conformal invariance.…

Statistical Mechanics · Physics 2022-01-12 Y. Minoguchi , P. Rabl , M. Buchhold

The existence of incompatible measurements, i.e. measurements which cannot be performed simultaneously on a single copy of a quantum state, constitutes an important distinction between quantum mechanics and classical theories. While…

Quantum Physics · Physics 2022-06-22 Krzysztof Mordasewicz , Jędrzej Kaniewski

Quantum field theory (QFT) on fractal spacetimes is a program aiming at quantizing the gravitational interaction consistently at all energy scales thanks to an intrinsically or dynamically induced multiscale or multifractal-like spacetime…

High Energy Physics - Theory · Physics 2026-03-26 Fabio Briscese , Gianluca Calcagni

Quantum field theory currently has a single standard mathematical characterization (the Standard Model), but no single accepted conceptual framework to interpret the mathematics. Many of these conceptualizations rely on intuitive concepts…

General Physics · Physics 2023-12-25 Christopher Thron

Establishing a notion of the quantum state that applies consistently across space and time could be a crucial step toward formulating a relativistic quantum theory. We give an operational meaning to multipartite quantum states over…

Quantum Physics · Physics 2026-04-14 Seok Hyung Lie , Hyukjoon Kwon

Quantum field theory (QFT) in classical spacetime has revealed interesting and puzzling aspects about gravitational systems, in particular black hole thermodynamics and its information processing. Although quantum gravitational effects may…

Quantum Physics · Physics 2018-05-24 Ding Jia

Universal quantum computation encoded over continuous variables can be achieved via Gaussian measurements acting on entangled non-Gaussian states. However, due to the weakness of available nonlinearities, generally these states can only be…

Quantum Physics · Physics 2021-12-02 Oussama Houhou , Darren W. Moore , Sougato Bose , Alessandro Ferraro

Commensurate scale relations relate observables to observables and thus are independent of theoretical conventions, such as the choice of intermediate renormalization scheme. The physical quantities are related at commensurate scales which…

High Energy Physics - Phenomenology · Physics 2007-05-23 Stanley J. Brodsky , Hung Jung Lu