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In quantum physics, measurement results are random but their statistics can be predicted assuming some knowledge about the system in the past. Additional knowledge from a future measurement deeply changes the statistics in the present and…

The quantum Zeno effect (QZE) predicts a slow-down of the time development of a system under rapidly repeated ideal measurements, and experimentally this was tested for an ensemble of atoms using short laser pulses for non-selective state…

Quantum Physics · Physics 2008-11-26 Almut Beige , Gerhard C. Hegerfeldt

Squeezed states of light have been successfully employed in interferometric gravitational-wave detectors to reduce quantum noise, thus becoming one of the most promising options for extending the astrophysical reach of the generation of…

Optics · Physics 2017-04-13 Patrick Kwee , John Miller , Tomoki Isogai , Lisa Barsotti , Matthew Evans

In quantum field theory there exist states for which the energy density is negative. It is important that these negative energy densities satisfy constraints, such as quantum inequalities, to minimize possible violations of causality, the…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Dan N. Vollick

Quantum weak measurement, measuring some observable quantities within the selected subensemble of the entire quantum ensemble, can produce many interesting results such as the superluminal phenomena. An outcome of such a measurement is the…

Quantum Physics · Physics 2017-01-24 Miao Zhang

We investigate the quantum statistical properties of the light emitted by a quantum well interacting with squeezed light from a degenerate subthreshold optical parametric oscillator. We obtain analytical solutions for the pertinent quantum…

Quantum Physics · Physics 2011-09-21 Eyob A. Sete , H. Eleuch

Experimental tests for assessing the physical reality of the hypothetical wave modes of quantum vacuum with zero-point energy are of fundamental importance for quantum field theories and cosmology. Physical effects like the Casimir effect…

Quantum Physics · Physics 2019-12-25 C. S. Unnikrishnan

Three different noise moments of field strength, intensity, and their correlations are simultaneously measured. For this purpose a homodyne cross-correlation measurement [W. Vogel, Phys. Rev. A 51, 4160 (1995)] is implemented by…

Quantum Physics · Physics 2017-04-26 B. Kühn , W. Vogel , M. Mraz , S. Köhnke , B. Hage

The sensitivity afforded by quantum sensors is limited by decoherence. Quantum error correction (QEC) can enhance sensitivity by suppressing decoherence, but it has a side-effect: it biases a sensor's output in realistic settings. If…

Quantum Physics · Physics 2022-04-20 Ivan Rojkov , David Layden , Paola Cappellaro , Jonathan Home , Florentin Reiter

Quantum information processing and computation requires high accuracy qubit configuration readout. In many practical schemes, the initial qubit configuration has to be inferred from readout that is a time-dependent weak measurement record.…

Quantum Physics · Physics 2025-12-17 Cesar Lema , Aleix Bou-Comas , Atithi Acharya , Vadim Oganesyan , Anirvan Sengupta

Quantum Mechanics (QM) predicts the correlation between measurements performed in remote regions of a spatially spread entangled state to be higher than allowed by the intuitive concepts of Locality and Realism (LR). This high correlation…

Quantum Physics · Physics 2019-04-17 Alejandro Hnilo , Mónica Agüero

Squeezed light has revolutionized quantum metrology by enhancing interferometry for sensitive applications such as the detection of gravitational waves. Squeezed light has also played a pivotal role in quantum information science with…

A large number of cosmological studies now suggest that roughly two-thirds of the critical energy density of the Universe exists in a component with negative pressure. If the equation of state of such an energy component varies with time,…

Astrophysics · Physics 2010-04-06 Asantha R. Cooray , Dragan Huterer

The conflict between Quantum Mechanics (QM) and Local Realism is most noticeable in the correlations observed between distant regions of a spatially spread entangled state. It has been hypothesized that transient deviations (from the values…

Quantum Physics · Physics 2024-04-16 Alejandro Hnilo , Mónica Agüero , Marcelo Kovalsky , Myriam Nonaka

We propose Gaussian quantum illumination(QI) protocol exploiting asymmetrically squeezed two-mode(ASTM) state that is generated by applying single-mode squeezing operations on each mode of an initial two-mode squeezed vacuum(TMSV) state, in…

Quantum Physics · Physics 2021-07-21 Yonggi Jo , Taek Jeong , Junghyun Kim , Duk Y. Kim , Yong Sup Ihn , Zaeill Kim , Su-Yong Lee

In a previous paper, a bound on the negative energy density seen by an arbitrary inertial observer was derived for the free massless, quantized scalar field in four-dimensional Minkowski spacetime. This constraint has the form of an…

General Relativity and Quantum Cosmology · Physics 2009-10-28 L. H. Ford , Thomas A. Roman

Noise is an important factor that influences the reliability of information acquisition, transmission, processing, and storage. In order to suppress the inevitable noise effects, a fault-tolerant information processing approach via quantum…

Quantum Physics · Physics 2026-03-27 Qi Song , Hongjing Li , Chengxi Yu , Jingzheng Huang , Ding Wang , Peng Huang , Guihua Zeng

An important yet perplexing result from work in the 90s and 00s is the near-unity value of the ratio of fluctuations in the vacuum energy density of quantum fields to the mean in a collection of generic spacetimes. This was done by way of…

General Relativity and Quantum Cosmology · Physics 2023-01-10 Hing-Tong Cho , Jen-Tsung Hsiang , Bei-Lok Hu

Current constraints on Einstein's weak equivalence principle (WEP) utilize the observed time delay between correlated particles of astronomical sources. However, the intrinsic time delay due to particle emission time is impossible to…

High Energy Astrophysical Phenomena · Physics 2018-09-26 H. Yu , F. Y. Wang

I discuss some theoretical ideas concerning the representation of quantum gravity as a Lorentz-symmetry-violating `medium' with non-trivial optical properties, which include a refractive index in `vacuo' and stochastic effects associated…

Astrophysics · Physics 2017-08-23 N. E. Mavromatos