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Loophole-Free Bell Tests and the Falsification of Local Realism
摘要： Quantum mechanics is strictly incompatible with local realism. It has been shown by Bell and others that it is possible, in principle, to experimentally differentiate between local realism and quantum mechanics. Numerous experiments have attempted to falsify local realism; however, they have consistently failed to close the detection loophole under strict locality conditions, thereby allowing local realistic explanations for their observations. In 2015, three experiments took place that tested local realism without the impediments of these significant loopholes. Between these three experiments, a substantial data set was collected. All of the collected data show a strong violation of local realism and strong support for quantum mechanics. This article reviews the theoretical basis of Bell tests and the affiliated loopholes, as well as the methods employed by these recent experiments and the implications of the results they observed.
关键词： Local Realism,CHSH Inequality,Loophole-Free Bell Test,CH Inequality,Quantum Mechanics
更新于2025-09-23 15:22:29
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A Quantum Field Approach for Advancing Optical Coherence Tomography Part I: First Order Correlations, Single Photon Interference, and Quantum Noise
摘要： Optical coherence tomography has become an important imaging technology in cardiology and ophthalmology, with other applications under investigations. Major advances in optical coherence tomography (OCT) imaging are likely to occur through a quantum field approach to the technology. In this paper, which is the first part in a series on the topic, the quantum basis of OCT first order correlations is expressed in terms of full field quantization. Specifically first order correlations are treated as the linear sum of single photon interferences along indistinguishable paths. Photons and the electromagnetic (EM) field are described in terms of quantum harmonic oscillators. While the author feels the study of quantum second order correlations will lead to greater paradigm shifts in the field, addressed in part II, advances from the study of quantum first order correlations are given. In particular, ranging errors are discussed (with remedies) from vacuum fluctuations through the detector port, photon counting errors, and position probability amplitude uncertainty. In addition, the principles of quantum field theory and first order correlations are needed for studying second order correlations in part II.
关键词： Plaque,Quantum mechanics,Interferometry,Ophthalmology,Noise,Vacuum,Cardiology,Arthritis,Optical coherence tomography
更新于2025-09-23 15:22:29
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On the quantum-mechanics of a single photon
摘要： It is shown that a Dirac(-type) equation for a rank-two bi-spinor field ψph on Minkowski (configuration) spacetime furnishes a Lorentz-covariant quantum-mechanical wave equation in position-space representation for a single free photon. This equation does not encounter any of the roadblocks that have obstructed previous attempts (by various authors) to formulate a quantum-mechanical photon wave equation. In particular, it implies that the photon wave function ψph yields conserved non-negative Born-rule-type quantum probabilities and that its probability current density four-vector transforms properly under Lorentz transformations. Moreover, the eigenvalues of the pertinent photon Dirac Hamiltonian and the vector eigenvalues of the photon momentum operator yield the familiar Einstein relations E = ?ω and p = ?k, respectively. Furthermore, these spin-1 wave modes are automatically transversal without the need of an additional constraint on the initial data. Some comments on other proposals to set up a photon wave equation are supplied as well.
关键词： probability current,wave function,quantum-mechanics,photon,Dirac-type equation,Born-rule,Einstein relations,transversal modes,Lorentz-covariant
更新于2025-09-23 15:21:21
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Coherent inflation for large quantum superpositions of levitated microspheres
摘要： We show that coherent in?ation (CI), namely quantum dynamics generated by inverted conservative potentials acting on the center of mass of a massive object, is an enabling tool to prepare large spatial quantum superpositions in a double-slit experiment. Combined with cryogenic, extreme high vacuum, and low-vibration environments, we argue that it is experimentally feasible to exploit CI to prepare the center of mass of a micrometer-sized object in a spatial quantum superposition comparable to its size. In such a hitherto unexplored parameter regime gravitationally-induced decoherence could be unambiguously falsi?ed. We present a protocol to implement CI in a double-slit experiment by letting a levitated microsphere traverse a static potential landscape. Such a protocol could be experimentally implemented with an all-magnetic scheme using superconducting microspheres.
关键词： levitated quantum micromechanics,macroscopic quantum superpositions,testing quantum mechanics,quantum interference
更新于2025-09-23 15:21:01
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Desarrollo de un simulador para el protocolo de criptografía cuántica E91 en un ambiente distribuido
摘要： The objective of this research work is the development of an application which is capable of simulating the behavior of one of the main developed protocols of quantum cryptography, the protocol E91. In order to achieve this objective, it was essential to carry out an exhaustive investigation of the main concepts, principles and theorems of quantum mechanics; as well as the study of other quantum cryptographic protocols and their development today. With all the collected information, the development of the application begun, starting with the definition of the requirements, then implementing and subsequently testing the application, which allows compiling all the work of analysis and design. The obtained results show the strengths and weaknesses of the application for the secure distribution of a quantum final key. Although this work is primarily the development of the implementation that simulates the behavior of the E91 protocol, it is essentially demonstrative.
关键词： Quantum mechanics,quantum protocol E91,RMI,quantum cryptography,E91 simulator,distributed programming
更新于2025-09-23 15:21:01
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Nonlinear Optics || Quantum-Mechanical Theory of the Nonlinear Optical Susceptibility
摘要： In this chapter, we use the laws of quantum mechanics to derive explicit expressions for the nonlinear optical susceptibility. The motivation for obtaining these expressions is at least three-fold: (1) these expressions display the functional form of the nonlinear optical susceptibility and hence show how the susceptibility depends on material parameters such as dipole transition moments and atomic energy levels, (2) these expressions display the internal symmetries of the susceptibility, and (3) these expressions can be used to make predictions of the numerical values of the nonlinear susceptibilities. These numerical predictions are particularly reliable for the case of atomic vapors, because the atomic parameters (such as atomic energy levels and dipole transition moments) that appear in the quantum-mechanical expressions are often known with high accuracy. In addition, since the energy levels of free atoms are very sharp (as opposed to the case of most solids, where allowed energies have the form of broad bands), it is possible to obtain very large values of the nonlinear susceptibility through the technique of resonance enhancement. The idea behind resonance enhancement of the nonlinear optical susceptibility is shown schematically in Fig. 3.1.1 for the case of third-harmonic generation. In part (a) of this figure, we show the process of third-harmonic generation in terms of the virtual levels introduced in Chapter 1. In part (b) we also show real atomic levels, indicated by solid horizontal lines. If one of the real atomic levels is nearly coincident with one of the virtual levels of the indicated process, the coupling between the radiation and the atom becomes particularly strong and the nonlinear optical susceptibility becomes large.
关键词： resonance enhancement,quantum mechanics,nonlinear optical susceptibility,third-harmonic generation,dipole transition moments,atomic energy levels
更新于2025-09-23 15:21:01
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Optomechanical Bell Test
摘要： Over the past few decades, experimental tests of Bell-type inequalities have been at the forefront of understanding quantum mechanics and its implications. These strong bounds on specific measurements on a physical system originate from some of the most fundamental concepts of classical physics—in particular that properties of an object are well-defined independent of measurements (realism) and only affected by local interactions (locality). The violation of these bounds unambiguously shows that the measured system does not behave classically, void of any assumption on the validity of quantum theory. It has also found applications in quantum technologies for certifying the suitability of devices for generating quantum randomness, distributing secret keys and for quantum computing. Here we report on the violation of a Bell inequality involving a massive, macroscopic mechanical system. We create light-matter entanglement between the vibrational motion of two silicon optomechanical oscillators, each comprising approx. 1010 atoms, and two optical modes. This state allows us to violate a Bell inequality by more than 4 standard deviations, directly confirming the nonclassical behavior of our optomechanical system under the fair sampling assumption.
关键词： Bell test,quantum mechanics,entanglement,nonclassical behavior,optomechanics
更新于2025-09-23 15:21:01
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Introduction to Quantum Electronics and Nonlinear Optics || Excursus on the Atomica??Molecular Theory of Substance
摘要： From fundamental physics we know well that a substance consists of molecules and atoms. Depending on the character and intensity of the interaction between atoms and molecules, a substance is in one of the following aggregate states: gas, liquid, solid, or plasma. Quantum electronics deals with all of these states, and we consider them in the order of an increasing degree of interaction between particles. We begin with an excursus on an isolated atom.
关键词： quantum mechanics,quantum electronics,atomic-molecular theory,substance states,Schr?dinger equation
更新于2025-09-23 15:19:57
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Theoretical investigation using DFT of quinoxaline derivatives for electronic and photovoltaic effects
摘要： Photovoltaic properties of solar cells based on fifteen organic dyes have been studied in this work. B3LYP/6-311G (d,p) methods are realized to obtain geometries and optimize the electronic properties, optical and photovoltaic parameters for some quinoxaline derivatives. The results showed that time dependent DFT investigations using the CAM-B3LYP method with the polarized split-valence 6-311G (d,p) basis sets and the polarizable continuum model PCM model were sensibly able to predict the excitation energies, the spectroscopy of the compounds. HOMO and LUMO energy levels of these molecules can make a positive impact on the process of electron injection and dye regeneration. Gaps energy ΔEg, short-circuit current density Jsc, light-harvesting efficiency LHE, injection driving force ΔGinject, total reorganization energy λtotal and open-circuit photovoltage Voc enable qualitative predictions about the reactivity of these dyes.
关键词： Computing methodology,TD-DFT,Energy,PCM,Optoelectronic,Particle physics,Quantum mechanics,Photovoltaic,Physics,Quinoxaline derivatives,Theoretical computer science,Solar cells,Molecular physics
更新于2025-09-23 15:19:57
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Different hydrogen bonding environments of the retinal protonated Schiff base control the photoisomerization in channelrhodopsin-2
摘要： The first event of the channelrhodopsin-2 (ChR2) photocycle, i.e. trans-to-cis photoisomerization, is studied by means of quantum mechanics/molecular mechanics, taking into account the flexible retinal environment in the ground state. By treating the chromophore at the ab initio multiconfigurational level of theory, we can rationalize the experimental findings based on pump–probe spectroscopy, explaining the different and more complex scenario found for ChR2 in comparison to other rhodopsins. In particular, we find that depending on the hydrogen bonding pattern, different excited states are involved, hence making it possible to suggest one pattern as the most productive. Moreover, after photoisomerization the structure of the first photocycle intermediate, P500, is characterized by simulating the infrared spectrum and compared to available experimental data. This was obtained by extensive molecular dynamics, where the chromophore is described by a semi-empirical method based on density functional theory. The results clearly identify which counterion is responsible for accepting the proton from the retinal Schiff base: the side chain of the glutamic acid E123.
关键词： FTIR spectroscopy,quantum mechanics/molecular mechanics,retinal Schiff base,photoisomerization,channelrhodopsin-2,hydrogen bonding,excited states,molecular dynamics
更新于2025-09-19 17:15:36