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We investigate the advantage of coherent superposition of two different coded channels in quantum metrology. In a continuous variable system, we show that the Heisenberg limit $1/N$ can be beaten by the coherent superposition without the…

Quantum Physics · Physics 2021-12-15 Dong Xie , Chunling Xu , An Min Wang

In this paper, we are exploring the feasibility of observing non-classical features of gravity in a low-energy regime in a quantum optomechanical experiment. If gravity is to have an underlying quantum nature, it should hold the most…

Quantum Physics · Physics 2019-05-03 Sahar Sahebdivan

We propose a method to prepare and verify spatial quantum superpositions of a nanometer-sized object separated by distances of the order of its size. This method provides unprecedented bounds for objective collapse models of the wave…

Quantum Physics · Physics 2011-07-08 O. Romero-Isart , A. C. Pflanzer , F. Blaser , R. Kaltenbaek , N. Kiesel , M. Aspelmeyer , J. I. Cirac

The correspondence principle suggests that quantum systems grow classical when large. Classical systems cannot violate Bell inequalities. Yet agents given substantial control can violate Bell inequalities proven for large-scale systems. We…

Quantum Physics · Physics 2021-02-10 Adam Bene Watts , Nicole Yunger Halpern , Aram Harrow

Quantum metrology based on quantum entanglement and quantum coherence improves the accuracy of measurement. In this paper, we briefly review the schemes of quantum metrology in various complex systems, including non-Markovian noise,…

Quantum Physics · Physics 2024-01-18 Qing Ai , Yang-Yang Wang , Jing Qiu

Complementarity is one of the main features of quantum physics that radically departs from classical notions. Here we consider the limitations that this principle imposes due to the unpredictability of measurement outcomes of incompatible…

Quantum Physics · Physics 2020-09-29 F. E. S. Steinhoff , M. C. de Oliveira

Quantum Neural Networks (QNNs) have achieved initial success in various tasks by integrating quantum computing and neural networks. However, growing concerns about their reliability and robustness highlight the need for systematic testing.…

Quantum Physics · Physics 2026-01-12 Minqi Shao , Jianjun Zhao

The quantum superposition principle, a key distinction between quantum physics and classical mechanics, is often perceived as a philosophical challenge to our concepts of reality, locality or space-time since it contrasts our intuitive…

Quantum Physics · Physics 2017-09-13 Sandra Eibenberger , Stefan Gerlich , Markus Arndt , Marcel Mayor , Jens Tüxen

Quantum coherence is a fundamental property of quantum systems, separating quantum from classical physics. Recently, there has been significant interest in the characterization of quantum coherence as a resource, investigating how coherence…

The field of quantum sensing explores the use of quantum phenomena to measure a broad range of physical quantities, of both static and time-dependent types. An important figure of merit for sensing time dependent signals is the spectral…

Quantum Physics · Physics 2019-12-05 Tuvia Gefen , Amit Rotem , Alex Retzker

We present and analyze a proposal for a macroscopic quantum delayed-choice experiment with massive mechanical resonators. In our approach, the electronic spin of a single nitrogen-vacancy impurity is employed to control the coherent…

Quantum Physics · Physics 2019-07-11 Wei Qin , Adam Miranowicz , Guilu Long , J. Q. You , Franco Nori

Field mediated entanglement experiments probe the quantum superposition of macroscopically distinct field configurations. We show that this phenomenon can be described by using a transparent quantum field theoretical formulation of…

General Relativity and Quantum Cosmology · Physics 2023-03-22 Lin-Qing Chen , Flaminia Giacomini , Carlo Rovelli

The spectral fluctuations of complex quantum systems, in appropriate limit, are known to be consistent with that obtained from random matrices. However, this relation between the spectral fluctuations of physical systems and random matrices…

Quantum Physics · Physics 2020-09-16 S. Harshini Tekur , M. S. Santhanam

The notion of a macroscopic quantum state must be pinned down in order to assess how well experiments probe the large-scale limits of quantum mechanics. However, the issue of quantifying so-called quantum macroscopicity is fraught with…

Quantum Physics · Physics 2025-03-12 Benjamin Yadin , Matteo Fadel

A software product line models the variability of highly configurable systems. Complete exploration of all valid configurations (the configuration space) is infeasible as it grows exponentially with the number of features in the worst case.…

Quantum Physics · Physics 2023-07-28 Joshua Ammermann , Tim Bittner , Domenik Eichhorn , Ina Schaefer , Christoph Seidl

The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test…

Quantum physics has intrigued scientists and philosophers alike, because it challenges our notions of reality and locality--concepts that we have grown to rely on in our macroscopic world. It is an intriguing open question whether the…

Quantum Physics · Physics 2014-10-02 Markus Arndt , Klaus Hornberger

Quantum superposition is central to quantum theory but challenges our concepts of reality and spacetime when applied to macroscopic objects like Schr\"odinger's cat. For that reason, it has been a long-standing question whether quantum…

Quantum Physics · Physics 2016-03-14 Rainer Kaltenbaek

One of the basic lessons of quantum theory is that one cannot obtain information on an unknown quantum state without disturbing it. Hence, by performing a certain measurement, we limit the other possible measurements that can be effectively…

Quantum Physics · Physics 2018-08-24 Erkka Haapasalo , Teiko Heinosaari , Takayuki Miyadera

We investigate the notion of "macroscopicity" in the case of large quantum spin systems and provide two main results. First, we motivate the Fisher information as a measure for the macroscopicity of quantum states. Second, we compare the…

Quantum Physics · Physics 2012-09-28 Florian Fröwis , Wolfgang Dür