Davisson–Germer experiment History and Overview[edit] According to Maxwell's equations in the late 19th century, light was thought to consist of waves of electromagnetic fields and matter was thought to consist of localized particles. However, this was challenged in Albert Einstein’s 1905 paper on the photoelectric effect, which described light as discrete and localized quanta of energy (now called photons), which won him the Nobel Prize in Physics in 1921. In 1927 Louis de Broglie presented his thesis concerning the wave-particle duality theory, which proposed the idea that all matter displays the wave-particle duality of photons.[2] According to de Broglie, for all matter and for radiation alike, the energy E of the particle was related to the frequency of its associated wave ν by the Planck relation: And that the momentum of the particle p was related to its wavelength by what is now known as the de Broglie relation: where h is Planck's constant. Early Experiments[edit] Experimental setup A breakthrough[edit] R.
Quantum entanglement Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently – instead, a quantum state may be given for the system as a whole. Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky and Nathan Rosen,[1] describing what came to be known as the EPR paradox, and several papers by Erwin Schrödinger shortly thereafter.[2][3] Einstein and others considered such behavior to be impossible, as it violated the local realist view of causality (Einstein referred to it as "spooky action at a distance"),[4] and argued that the accepted formulation of quantum mechanics must therefore be incomplete. History[edit] However, they did not coin the word entanglement, nor did they generalize the special properties of the state they considered. Concept[edit] Meaning of entanglement[edit] Apparent paradox[edit] The hidden variables theory[edit]
Stern–Gerlach experiment Basic theory and description[edit] Quantum spin versus classical magnet in the Stern–Gerlach experiment Basic elements of the Stern–Gerlach experiment. The Stern–Gerlach experiment involves sending a beam of particles through an inhomogeneous magnetic field and observing their deflection. The results show that particles possess an intrinsic angular momentum that is closely analogous to the angular momentum of a classically spinning object, but that takes only certain quantized values. The experiment is normally conducted using electrically neutral particles or atoms. If the experiment is conducted using charged particles like electrons, there will be a Lorentz force that tends to bend the trajectory in a circle (see cyclotron motion). Spin values for fermions. Electrons are spin-1⁄2 particles. For electrons there are two possible values for the spin angular momentum that is measured along an axis. The constants c1 and c2 are complex numbers. one of the two possible values of j is found.
First Quantum Effects Seen in Visible Object Science has proved contradiction. Unless, of course, we know that contradiction is impossible, and that the law of non-contradiction was used in the process of "proving" contradiction, making it a self-defeating argument. Now, any rational person will know that nothing can be and not be at the same time, so this whole thing is absurd on its face, unless you take it to mean both are happening in some kind of figurative, unreal sense, in which case the article is luridly, and I suspect purposefully, misleading. Take away the breaking of the law of non-contradiction. These things are unknowable until they actually occur, yet follow laws of probability? Just thought I would be polemical and challenge the smug consensus here.
Bell test experiments Bell test experiments or Bell's inequality experiments are designed to demonstrate the real world existence of certain theoretical consequences of the phenomenon of entanglement in quantum mechanics which could not possibly occur according to a classical picture of the world, characterised by the notion of local realism. Under local realism, correlations between outcomes of different measurements performed on separated physical systems have to satisfy certain constraints, called Bell inequalities. John Bell derived the first inequality of this kind in his paper "On the Einstein-Podolsky-Rosen Paradox".[1] Bell's Theorem states that the predictions of quantum mechanics cannot be reproduced by any local hidden variable theory. The term "Bell inequality" can mean any one of a number of inequalities satisfied by local hidden variables theories; in practice, in present day experiments, most often the CHSH; earlier the CH74 inequality. Conduct of optical Bell test experiments[edit] Pan et al.'
Bell's theorem Bell's theorem is a no-go theorem famous for drawing an important distinction between quantum mechanics (QM) and the world as described by classical mechanics. In its simplest form, Bell's theorem states:[1] No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics. In the early 1930s, the philosophical implications of the current interpretations of quantum theory were troubling to many prominent physicists of the day, including Albert Einstein. In a well-known 1935 paper, Einstein and co-authors Boris Podolsky and Nathan Rosen (collectively "EPR") demonstrated by a paradox that QM was incomplete. This provided hope that a more-complete (and less-troubling) theory might one day be discovered. In the 1950s, antecedent probabilistic theorems were published by Jean Bass, Emil D. These three key concepts – locality, realism, freedom – are highly technical and much debated. Overview[edit] , local realism predicts or less. Bell inequalities[edit]
Popper's experiment Popper's experiment is an experiment proposed by the philosopher Karl Popper. As early as 1934 he was suspicious of, and was proposing experiments to test, the Copenhagen interpretation, a popular subjectivist interpretation of quantum mechanics.[1][2] Popper's experiment is a realization of an argument similar in spirit to the thought experiment of Einstein, Podolsky and Rosen (the EPR paradox) although not as well known. There are various interpretations of quantum mechanics that do not agree with each other. Despite their differences, they are experimentally nearly indistinguishable from each other. The most widely known interpretation of quantum mechanics is the Copenhagen interpretation put forward by Niels Bohr. It says that observations lead to a wavefunction collapse, thereby suggesting the counter-intuitive result that two well separated, non-interacting systems require action-at-a-distance. Popper's proposed experiment[edit] Popper wrote: The debate[edit] They concluded that: . .
Personal and Historical Perspectives of Hans Bethe Schrödinger's cat Schrödinger's cat: a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Schrödinger's cat is a thought experiment, sometimes described as a paradox, devised by Austrian physicist Erwin Schrödinger in 1935.[1] It illustrates what he saw as the problem of the Copenhagen interpretation of quantum mechanics applied to everyday objects. Origin and motivation[edit] Real-size cat figure in the garden of Huttenstrasse 9, Zurich, where Erwin Schrödinger lived 1921 – 1926. The thought experiment[edit] Schrödinger wrote:[1][10] One can even set up quite ridiculous cases. You are the only contemporary physicist, besides Laue, who sees that one cannot get around the assumption of reality, if only one is honest.
Quantum Mechanics! - First Quantum Effects Seen in Visible Object Elitzur–Vaidman bomb tester Bomb-testing problem diagram. A - photon emitter, B - bomb to be tested, C,D - photon detectors. Mirrors in the lower left and upper right corners are half-silvered. In physics, the Elitzur–Vaidman bomb-testing problem is a thought experiment in quantum mechanics, first proposed by Avshalom Elitzur and Lev Vaidman in 1993.[1] An actual experiment demonstrating the solution was constructed and successfully tested by Anton Zeilinger, Paul Kwiat, Harald Weinfurter, and Thomas Herzog from the University of Innsbruck, Austria and Mark A. Problem[edit] Consider a collection of bombs, of which some are duds. Solution[edit] Start with a Mach–Zehnder interferometer and a light source which emits single photons. When a photon's state is non-deterministically altered, such as interacting with a half-silvered mirror where it non-deterministically passes through or is reflected, the photon undergoes quantum superposition, whereby it takes on all possible states and can interact with itself. P.
Quantum eraser experiment The double-slit quantum eraser experiment described in this article has three stages:[1] First, the experimenter reproduces the interference pattern of Young's double-slit experiment by shining photons at the double-slit interferometer and checking for an interference pattern at the detection screen.Next, the experimenter marks through which slit each photon went, without disturbing its wavefunction, and demonstrates that thereafter the interference pattern is destroyed. This stage indicates that it is the existence of the "which-path" information that causes the destruction of the interference pattern.Third, the "which-path" information is "erased," whereupon the interference pattern is recovered. (Rather than removing or reversing any changes introduced into the photon or its path, these experiments typically produce another change that obscures the markings earlier produced.) Quantum erasure technology can be used to increase the resolution of advanced microscope.[3] Introduction[edit]
Delayed choice quantum eraser A delayed choice quantum eraser, first performed by Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. The delayed choice quantum eraser experiment investigates a paradox. Delayed choice experiments have uniformly confirmed the seeming ability of measurements made on photons in the present to alter events occurring in the past. Introduction[edit] In the basic double slit experiment, a beam of light (usually from a laser) is directed perpendicularly towards a wall pierced by two parallel slit apertures. Which-path information and the visibility of interference fringes are hence complementary quantities. However, in 1982, Scully and Drühl found a loophole around this interpretation.[11] They proposed a "quantum eraser" to obtain which-path information without scattering the particles or otherwise introducing uncontrolled phase factors to them. A simple quantum eraser experiment[edit] Figure 1. In the two diagrams in Fig. 1, photons are emitted one at a time from a laser symbolized by a yellow star.
Wheeler's delayed choice experiment Wheeler's delayed choice experiment is actually several thought experiments in quantum physics, proposed by John Archibald Wheeler, with the most prominent among them appearing in 1978 and 1984.[1] These experiments are attempts to decide whether light somehow "senses" the experimental apparatus in the double-slit experiment it will travel through and adjusts its behavior to fit by assuming the appropriate determinate state for it, or whether light remains in an indeterminate state, neither wave nor particle, and responds to the "questions" asked of it by responding in either a wave-consistent manner or a particle-consistent manner depending on the experimental arrangements that ask these "questions."[2] This line of experimentation proved very difficult to carry out when it was first conceived. Introduction[edit] "Wheeler's delayed choice experiment" refers to a series of thought experiments in quantum physics, the first being proposed by him in 1978. Simple interferometer[edit]