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Elitzur–Vaidman bomb tester

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. Kasevich of Stanford University in 1994.[2] It employs a Mach–Zehnder interferometer for ascertaining whether a measurement has taken place. 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. Step-by-step explanation[edit] If the bomb is a dud: The bomb will pass the wave, so the situation is as described above, without a bomb. See also[edit] Related:  Founding experiments

Mach–Zehnder interferometer Figure 1. The Mach–Zehnder interferometer is frequently used in the fields of aerodynamics, plasma physics and heat transfer to measure pressure, density, and temperature changes in gases. In this figure, we imagine analyzing a candle flame. Either output image may be monitored. Introduction[edit] The Mach–Zehnder interferometer is a highly configurable instrument. Figure 2. Collimated sources result in a nonlocalized fringe pattern. The Mach–Zehnder interferometer's relatively large and freely accessible working space, and its flexibility in locating the fringes has made it the interferometer of choice for visualizing flow in wind tunnels[6][7] and for flow visualization studies in general. Mach–Zehnder interferometers are used in electro-optic modulators, electronic devices used in various fibre-optic communications applications. How it works[edit] Set-up[edit] A collimated beam is split by a half-silvered mirror. Properties[edit] In other words: Figure 3. We also note that: See also[edit]

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]

Interaction-free measurement In physics, interaction-free measurement is a type of measurement in quantum mechanics that detects the position or state of an object without an interaction occurring between it and the measuring device. Examples include the Renninger negative-result experiment, the Elitzur–Vaidman bomb-testing problem, and certain double-cavity optical systems. See also[edit] Counterfactual definiteness References[edit] Mauritius Renninger, Messungen ohne Storung des Messobjekts (Observations without disturbing the object), (1960) Zeitschrift für Physik, 158 pp 417-421.Mauritius Renninger, (1953) Zeitschrift für Physik, 136 p. 251Louis de Broglie, The Current Interpretation of Wave Mechanics, (1964) Elsevier, Amsterdam.

Delayed choice quantum eraser A delayed choice quantum eraser, first performed by Yoon-Ho Kim, R. Yu, S.P. Kulik, Y.H. Shih and Marlan O. Scully,[1] and reported in early 1999, is an elaboration on the quantum eraser experiment that incorporates concepts considered in Wheeler's delayed choice experiment. 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. 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. Delayed choice[edit] The experiment of Kim et al. (2000)[edit]

Alain Aspect Alain Aspect (French: [aspɛ] ( ); born 15 June 1947) is a French physicist noted for his experimental work on quantum entanglement. Biography[edit] Aspect is a graduate of the École Normale Supérieure de Cachan (ENS Cachan). In the early 1980s, while working on his PhD thesis[1] from the lesser academic rank of lecturer, he performed the elusive "Bell test experiments" that showed that Albert Einstein, Boris Podolsky and Nathan Rosen's reductio ad absurdum of quantum mechanics, namely that it implied 'ghostly action at a distance', did in fact appear to be realised when two particles were separated by an arbitrarily large distance (see EPR paradox). If quantum theory is correct, the determination of an axis direction for the polarization measurement of one photon, forcing the wave function to 'collapse' onto that axis, will influence the measurement of its twin. Aspect was deputy director of the French "grande école" SupOptique until 1994. Alain Aspect in Budapest, 2013 See also[edit]

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. Nevertheless, it has proven very valuable over the years since it has led researchers to provide "increasingly sophisticated demonstrations of the wave–particle duality of single quanta.

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]

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. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. This poses the question of when exactly quantum superposition ends and reality collapses into one possibility or the other. 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. Schrödinger wrote:[1][10]