Encyclopedia > Q > 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18
Quantitative revolution The quantitative revolution was one of the four major turning points in the history of geography (the other three being regional geography, environmental determinism and critical geography). The quantitative revolution occurred in the 1950s through to the 1960s and marked a rapid change in the method behind geographical research.
Quantitative trait locus Inheritance of quantitative traits refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to the interactions between two or more genes and their environment (also called Polygenic inheritance). Though not necessarily genes themselves, quantitative trait loci (QTLs) are stretches of DNA that are closely linked to the genes that underlie the trait in question.
Quantities of information The mathematical theory of information is based on probability theory and statistics, and measures information with several quantities of information. The choice of logarithmic base in the following formulae determines the unit of information entropy that is used.
Quantity adjustment In economics, the concept of quantity adjustment refers to one possible result of supply and demand disequilibrium in a market, either due to or in the absence of external constraints on the market. In the textbook story, if the quantity demanded does not equal the quantity supplied in a market, price adjustment is the rule: if there is a market surplus or glut (excess supply), prices fall, ending the glut, while a shortage (excess demand) causes price rises.
Quantity surveyor A Quantity Surveyor (QS) is a professional person working within the construction industry. The role of the QS is, in general terms, to manage and control costs within construction projects and may involve the use of a range of management procedures and technical tools to achieve this goal.
Quantization Quantization is the procedure of constraining something to a discrete set of values, such as an integer, rather than a continuous set of values, such as a real number. Quantization in specific domains is discussed in:
Quantization (linguistics) In linguistics, a quantized expression is such that, whenever it is true of some entity, it is not true of any proper subparts of that entity. Example: If something is an "apple", then no proper subpart of that thing is an "apple".
Quantization (music) In digital music processing technology, quantization is the process of aligning a set of musical notes to conform to a grid. The most frequent application of quantization in this context lies within MIDI application software.
Quantization (physics) In physics, quantization is a procedure for constructing a quantum field theory starting from a classical field theory. This is a generalization of the procedure for building quantum mechanics from classical mechanics.
Quantization (signal processing) In digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values.
Quantization (sound processing) In signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values. This article describes aspects of quantization related to sound signals.
Quantization error When converting from an analog signal to a digital signal, error is unavoidable. An analog signal is continuous, with ideally infinite accuracy, while the digital signal's accuracy is dependent on the quantization resolution, or number of bits of the analog to digital converter.
Quantization noise Quantization noise is a noise error introduced by quantization in the analogue to digital conversion (ADC) process in telecommunication systems and signal processing. It is a rounding error between the analogue input voltage to the ADC and the output digitized value.
Quantock Lodge Quantock Lodge is a nineteenth-century mansion located near the hamlet of Aley, near the village of Over Stowey in the English county of Somerset. It was the family home of Henry Labouchere, 1st Baron Taunton, and in the 1960s was purchased by David Peaster, the headmaster of Cotham School in Bristol.
Quantrill's Raiders Quantrill's Raiders were a group of Confederate bushwhackers who followed and fought under William Clarke Quantrill, an Ohio schoolteacher who relocated to Kansas and transformed a motley group of Southern-sympathizing farmers and townsmen living behind Union lines into one of the Confederacy's most effective and electric guerrilla units. The name "Quantrill's Raiders" seems to have been attached to the group long after the war; indeed, the members would later have reunions under that name.
Quantrix Quantrix is a powerful alternative to traditional spreadsheets, based on the same novel concepts and layout as the seminal Lotus Improv. It was originally developed for NeXTSTEP and OPENSTEP by Lighthouse Design, the famous NeXT-based "virtual development company".
Quantum acoustics In physics, quantum acoustics is the study of sound under conditions such that quantum mechanical effects are germane. For most applications, classical mechanics are sufficient to accurately describe the physics of sound.
Quantum aesthetics Quantum Aesthetics is a movement that was inaugurated by Gregorio Morales at the end of the 1990s with his work “El cadaver de Balzac” or Balzac's Corpse (1998). Here he defined the objectives of the movement in the phrase “mystery and difference”.
Quantum Art Quantum Art, founded in 1998, is a web content management software company headquartered in San Francisco, California. Quantum Art helps organizations treat information, not as documents or pages, but as lightweight content applications.
Quantum biology Quantum biology is the scientific study of biological processes in terms of quantum mechanics. This nascent field is one of the first efforts to apply quantum theory to systems more macroscopic than the atomic or subatomic realms generally described by quantum theory.
Quantum bogodynamics Quantum bogodynamics is a humorous theory arising within hacker culture that characterises the universe in terms of sources of fictional fundamental particles; bogons. There are bogon sources (such as politicians, used-car salesmen, TV evangelists, and suits in general), bogon sinks (such as taxpayers and computers), and bogosity potential fields.
Quantum brain dynamics In neuroscience, quantum brain dynamics (QBD) is a proposed theory to explain the function of the brain within the framework of quantum field theory. Although there are many blank areas in understanding the brain dynamics and especially how it gives rise to conscious experience it should be noted that quantum mechanics is only conisdered by some to be capable of explaining the enigma of consciousness.
Quantum cascade laser The quantum cascade laser or QC laser is a unipolar semiconductor laser. Unlike conventional semiconductor lasers, the optical transitions occur between electric subbands rather than between the conduction band and valence bands.
Quantum cellular automata Quantum Cellular Automata is any device designed to represent data and perform computation, regardless of the physics principles it exploits and materials used to build it, must have two fundamental properties: distinguishability and conditional change of state. The latter implying the former.
Quantum circuit In quantum mechanics, a quantum circuit is a specific model for a quantum computational device. Experiments have already been carried out which can be regarded as implementing a seven-qubit quantum circuit that implements Shor's algorithm.
Quantum cloning Quantum cloning is the process that takes an arbitrary, unknown quantum state and makes an exact copy without altering the original state in any way. In Dirac notation, the process of quantum cloning is described by:
Quantum coherence Quantum coherence refers to the condition of a quantum system whose constituents are in-phase. That is, the various states that make up the combined wavefunction have a fixed phase relationship with one another, making them correlated to one another as described by quantum mechanics.
Quantum cohomology In mathematics, specifically in symplectic topology and algebraic geometry, a quantum cohomology ring is an extension of the ordinary cohomology ring of a closed symplectic manifold. It comes in two versions, called small and big; in general, the latter is more complicated and contains more information than the former.
Quantum compression The Quantum compression format is a somewhat obscure data compression method invented by a company called Cinematronics (written by an author identified as David Stafford). Rights to it were purchased at some point by Microsoft, and Quantum is one of the possible compression methods in a CAB archive.
Quantum computer A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, the data is measured by qubits.
Quantum correlation In Bell test experiments the term quantum correlation has come to mean the expectation value of the product of the outcomes on the two sides. In the paper that inspired the Bell tests -- John Bell's of 1964 -- it was assumed that the outcomes A and B could each only take one of two values, -1 or +1.
Quantum cosmology In theoretical physics, quantum cosmology is a young field attempting to study the effect of quantum mechanics on the earliest moments of the universe after the Big Bang. Despite many attempts, the field remains a rather speculative branch of quantum gravity.
Quantum cryptography Quantum cryptography uses quantum mechanics for secure communications. Unlike traditional cryptography, which employs classical mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is based on the quantum physics of information.
Quantum Critical Point A Quantum critical point is a special class of continuous phase transition that takes place at the absolute zero of temperature, typically in a material where the phase transition temperature has been driven to zero by the application of a pressure, field or through doping.
Quantum damped harmonic oscillator The quantum damped harmonic oscillator combines concepts from the classical damped harmonic oscillator and the quantum harmonic oscillator. An overview of the quantum damped harmonic oscillator can be found in a paper by Depp The Quantum Damped Harmonic Oscillator.
Quantum darwinism Quantum darwinism is a theory explaining the emergence of the classical world from the quantum world as due to a process of Darwinian selection. It is proposed by Wojciech Zurek and a group of collaborators including Ollivier, Poulin, Paz and Blume-Kohout.
Quantum decoherence In quantum mechanics, quantum decoherence is the mechanism by which quantum systems interact with their environments to exhibit probabilistically additive behavior - a feature of classical physics - and give the appearance of wavefunction collapse. Decoherence occurs when a system interacts with its environment, or any complex external system, in such a thermodynamically irreversible way that ensures different elements in the quantum superposition of the system+environment's wavefunction can no longer interfere with each other.
Quantum degeneracy A quantum degeneracy is a quantum eigenvalue which has more than one linearly independent eigenvector. For instance, the quantum degeneracy of the 1s^1 electron configuration within a hydrogen atom is two in the absence of an external magnetic field, because there are two linearly independent 1s spin-orbitals with the same total energy.
Quantum dot A quantum dot is a semiconductor nanostructure that confines the motion of conduction band electrons, valence band holes, or excitons (pairs of conduction band electrons and valence band holes) in all three spatial directions. The confinement can be due to electrostatic potentials (generated by external electrodes, doping, strain, impurities), due to the presence of an interface between different semiconductor materials (e.
Quantum dot laser A quantum dot laser succeeds in minimizing temperature-sensitive output fluctuations, something not possible with previous semiconductor lasers. Fujitsu and the University of Tokyo have developed a 10 Gbit/s quantum dot laser not affected by temperature, for use in optical data communications and optical networks.
Quantum efficiency Quantum efficiency (QE) is a quantity defined for a photosensitive device such as photographic film or a charge-coupled device (CCD) as the percentage of photons hitting the photoreactive surface that will produce an electron–hole pair. It is an accurate measurement of the device's sensitivity.
Quantum electrodynamics Quantum electrodynamics (QED) is a relativistic quantum field theory of electromagnetism. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange by photons, whether the interaction is between light and matter or between two charged particles.
Quantum electrochemistry The scientific school of Quantum electrochemistry began to form in the 1960s under Revaz Dogonadze. Generally speaking, the field is comprised of the notions arising in electrodynamics, quantum mechanics, and electrochemistry; and so is studied by a very large array of different professional researchers.
Quantum entanglement Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated. This leads to correlations between observable physical properties of the systems.
Quantum eraser experiment In physics, the quantum eraser experiment is a double-slit experiment that demonstrates several laws of Quantum Mechanics, including wave-particle duality which seeks to explain certain wave and particle properties of matter, complementarity and the Copenhagen interpretation which outline the idea that, in QM, to gain an accurate measurement of one aspect of certain experimental subjects is to lose precision in its counterpart (much like attempting to view both sides of a coin at once). The experiment also utilizes a special crystal for its ability to produce photon pairs from a single photon and the use of an interferometer to explore the wave-like nature of an object.
Quantum error correction Quantum error correction is for use in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is essential if one is to achieve fault-tolerant quantum computation that can deal not just with noise on stored quantum information, but also with faulty quantum gates, faulty quantum preparation, and faulty measurements.
Quantum evolution Quantum evolution was a component of George Gaylord Simpson's (1902-1984) multi-tempoed theory of evolutionary change. According to Simpson (1944), some lineages in the fossil record evolved with extraordinary slowness, others more rapidly.
Quantum Effect Devices Quantum Effect Devices was a company originally named Quantum Effect Design, incorporated in 1991. The three founders, Tom Riordan, Earl Killian and Ray Kunita were senior managers at MIPS Computer Systems Inc..
Quantum Efficiency of a solar cell Quantum efficiency (QE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell. QE therefore relates to the response of a solar cell to the various wavelengths in the spectrum of light shining on the cell.
Quantum field theory Quantum field theory (QFT) is the quantum theory of fields. It provides a theoretical framework, widely used in particle physics and condensed matter physics, in which to formulate consistent quantum theories of many-particle systems, especially in situations where particles may be created and destroyed.
Quantum field theory in curved spacetime Quantum field theory in curved spacetimes is an extension of standard quantum field theory to curved spacetimes. A general prediction of this theory is that particles can be created in strong gravitational fields.
Quantum finite automata In quantum computing, quantum finite automata or QFA are a quantum analog of probabilistic automata. They are related to quantum computers in a similar fashion as finite automata are related to Turing machines.
Quantum flavordynamics In quantum mechanics, quantum flavordynamics (or "flavourdynamics") is a mathematical model used to describe the interaction of flavored particles (weak force) through the exchange of intermediate vector bosons, but the term is rarely used by practicing particle physicists.
Quantum flux parametron Invented by Eiichi Goto at the University of Tokyo, the Quantum Flux Parametron (QFP) is an improvement over his earlier parametron based digital logic technology. Unlike its predecessor, QFP uses superconducting Josephson junctions on integrated circuits to improve speed and energy efficiency enormously.
Quantum foam Quantum foam, also referred to as spacetime foam, is a concept in quantum mechanics, devised by John Wheeler in 1955. The foam is a qualitative description of the turbulence that the phenomenon creates at extremely small distances of the order of the Planck length.
Quantum Fourier transform The quantum Fourier transform is the discrete Fourier transform with a particular decomposition into a product of simpler unitary matrices. Using this decomposition, the discrete Fourier transform can be implemented as a quantum circuit consisting of Hadamard gates and controlled phase shift gates.
Quantum geometry In theoretical physics, quantum geometry is the set of new mathematical concepts generalizing the concepts of geometry whose understanding is necessary to describe the physical phenomena at very short distance scales (comparable to Planck length). At these distances, quantum mechanics has a profound effect on physics.
Quantum gravity Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. The ultimate goal of some is a unified framework for all fundamental forces—a "theory of everything".
Quantum gravity epoch In physical cosmology, the quantum gravity epoch is the first era in the history of the Universe according to the standard Big Bang cosmology. In this era, the effects of quantum gravity such as fluctuating topology of space are commonplace.
Quantum GIS Quantum GIS (often abbreviated to QGIS) is an open source GIS (mapping) application which is similar to commercial mapping packages. Because it is distributed as an opensource application under the GNU distribution license, Quantum GIS can be reprogrammed to perform different or more specialist tasks.
Quantum harmonic oscillator The quantum harmonic oscillator is the quantum mechanical analogue of the classical harmonic oscillator. It is one of the most important model systems in quantum mechanics because, as in classical mechanics, a wide variety of physical situations can be reduced to it either exactly or approximately.
Quantum heterostructure Quantum heterostructure is a heterostructure in a substrate (usually a semiconductor material), with size restricting the movements of the charge carriers and forcing them into a quantum confinement, leading to formation of a set of discrete energy levels the carriers can exist at. Quantum heterostructures have sharper density of states than structures of more conventional sizes.
Quantum history In some physics theories, choosing a 3-geometry via spin network and 4-geometry via spin foam, any superposition of spin networks is called a kinematical state and any superposition of spin foams is called a quantum history.
Quantum hydrodynamics Quantum hydrodynamics is more than the study of superfluidity. Some of the main subjects in quantum hydrodynamics are quantum turbulence, quantized vortices, first, second and third sound, and quantum solvents.
Quantum Hall effect The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance Ď takes on the quantized values
Quantum chemistry Quantum chemistry is a branch of theoretical chemistry, which applies quantum mechanics and quantum field theory to address issues and problems in chemistry. The description of the electronic behavior of atoms and molecules as pertaining to their reactivity is one of the applications of quantum chemistry.
Quantum chromodynamics Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (colour force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion). QCD is a quantum field theory of a special kind called a non-abelian gauge theory.
Quantum immortality Quantum immortality is the controversial metaphysical speculation deriving from the quantum suicide thought experiment that states the many-worlds interpretation of quantum mechanics implies that conscious beings are immortal.
Quantum indeterminacy Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics. Prior to quantum physics, it was thought that (a) a physical system had a determinate state which uniquely determined all the values of its measurable properties, and conversely (b) the values of its measurable properties uniquely determined the state.
Quantum information In quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-state quantum system.
Quantum information science Quantum information science concerns information science that depends on quantum effects in physics. It includes theoretical issues in computational models as well as more experimental topics in quantum physics including what can and cannot be done with quantum information.
Quantum level Quantum levels are fixed levels with a logarithmic, descending quantum pattern in the visible spectrum of light that can be observed through a spectrometer while looking at intense flows of electricity through the various halides on the periodic table in a vacuum tube. They also have some use in chemistry when dealing with the movement of electrons to different orbital levels around the atom and the energy levels involved in such actions.
Quantum logic In mathematical physics and quantum mechanics, quantum logic is an operator algebraic system for constructing and manipulating logical combinations of quantum mechanical events. It can be regarded as a kind of propositional logic suitable for understanding the apparent anomalies regarding quantum measurement, most notably those concerning composition of measurement operations of complementary variables.
Quantum Link Reloaded Quantum Link Reloaded is a re-implementation of the original Quantum Link (Q-Link) online service for the Commodore 64 home computer system. The formal introduction of Quantum Link Reloaded was held on the 20th Anniversary of the introduction of Quantum Link, November 5, 2005.
Quantum mechanical Bell test prediction In physics, the quantum mechanical Bell test prediction is the prediction that quantum mechanics would give for the correlation probabilities for a set of measurements performed on a quantum entangled state. An important outcome of this prediction is that it violates the Bell inequality, which, as a result, has serious implications for the interpretation of quantum mechanics.
Quantum mechanics Quantum mechanics is a fundamental branch of theoretical physics with wide applications in experimental physics that replaces classical mechanics and classical electromagnetism at the atomic and subatomic levels. It is the underlying mathematical framework of many fields of physics and chemistry, including condensed matter physics, solid-state physics, atomic physics, molecular physics, computational chemistry, quantum chemistry, particle physics, and nuclear physics.
Quantum mechanics, philosophy and controversy Quantum mechanics has had a profound effect on philosophy. Determinism is a philosophical view that the universe is governed by determinism if given a specific state of the universe at a specific time, the future state of the universe is fixed as a matter of natural law.
Quantum metrology Quantum metrology is the study of making high resolution measurements of parameters using quantum theory to describe the physical systems. This can give rise to measurements which give better precision than the same measurement performed in a classical framework.
Quantum mind The quantum mind theory is founded on the premise that quantum theory is necessary to fully understand the mind and brain, particularly concerning an explanation of consciousness. This is considered a minority opinion in science, although it does have the support of the well-known mathematical physicist Sir Roger Penrose.
Quantum mirage In physics, a quantum mirage is a peculiar result in quantum chaos. Every system of quantum dynamical billiards will exhibit an effect called scarring, where the quantum probability density shows traces of the paths a classical billiard ball would take.
Quantum mutual information In quantum information theory, quantum mutual information, or von Neumann mutual information, is a measure of correlation between subsystems of quantum state. It is the quantum mechanical analog of Shannon mutual information.
Quantum Monte Carlo Quantum Monte Carlo is a large class of computer algorithms that simulate quantum systems with the idea of solving the many-body problem. They use, in one way or another, the Monte Carlo method to handle the many dimensional integrals that arise.
Quantum network The idea of a quantum network emerged after successful experiments on quantum teleportation. When two companies (one from Switzerland, 'idQuantique', and another from the USA, 'MagiQTech') released practcal communication devices based upon the rules of quantum mechanics, the need for a secure network capable of utilizing quantum principles was realized.
Quantum operation In quantum mechanics, a quantum operation is a mathematical formalism used to describe a broad class of transformations that a quantum mechanical system can undergo. This formalism describes not only time evolution or symmetry transformations of isolated systems, but also transient interactions with an environment for purposes of measurement.
Quantum phase transition In physics, a quantum phase transition (QPT) is a phase transition between different quantum phases (phases of matter at zero temperature). Contrary to classical phase transitions, quantum phase transitions can be only be accessed by varying a physical parameter - such as magnetic field or pressure - at absolute zero temperature.
Quantum probability Quantum probability was developed in the 1980's as a noncommutative analog of the Kolmogorovian stochastic processes theory. One of its aims is to clarify the probabilistic mathematical foundations of quantum theory and its statistical interpretation.
Quantum programming language Quantum Programming Languages are programming languages that can be used to write programs for quantum computers. Generally, such languages attempt to provide high-level constructs for expressing quantum algorithms.
Quantum Philosophy (book) Quantum Philosophy is a book by the physicist Roland Omnès, in which he aims to show the non-specialist reader how modern developments in quantum mechanics allow the recovery of our common sense view of the world.
Quantum satis Quantum Satis (abbreviation qs or QS) is a Latin term meaning The amount which is needed. It has its origins as a quantity specification in medicine and pharmacology, but is also used in the same function in food regulations and food safety laws in the European Community.
Quantum singularity (fiction) In science fiction, the term quantum singularity is used to refer to many different phenomena, which often approximately resemble a gravitational singularity in the scientific sense in that they are massive, localized distortions of space and time. The name invokes one of the most fundamental problems remaining in modern physics: the difficulty in merging Einstein's Theory of Relativity (which includes singularities within its models of black holes) and quantum mechanics.
Quantum solid In physics, a quantum solid is a type of solid that is "intrinsically restless", in the sense that atoms continuously vibrate about their position and exchange places even at the absolute zero of temperature. The archetypal quantum solid is low density solid helium.
Quantum solvent A quantum solvent is essentially a superfluid (aka a quantum liquid) used to dissolve another chemical species. Any superfluid can theoretically act as a quantum solvent, however in practice the only viable superfluid medium that can currently be used is helium-4, and it has been successfully accomplished in controlled conditions.
Quantum sort A quantum sort is any sorting algorithm that runs on a quantum computer. Such an algorithm could at best be linearly faster than any existing sort algorithm (if based on comparisons like classical algorithms), but no such algorithm has actually been implemented.
Quantum statistical mechanics Quantum statistical mechanics is the study of statistical ensembles of quantum mechanical systems. A statistical ensemble is described by a density operator S, which is a non-negative, self-adjoint, trace-class operator of trace 1 on the Hilbert space H describing the quantum system.
Quantum suicide In quantum mechanics, quantum suicide is a thought experiment which was independently proposed in 1987 by Hans Moravec and in 1988 by Bruno Marchal, and further developed by Max Tegmark in 1998Tegmark, Max The Interpretation of Quantum Mechanics: Many Worlds or Many Words?, 1998, that attempts to distinguish between the Copenhagen interpretation of quantum mechanics and the Everett many-worlds interpretation by means of a variation of the Schrödinger's cat experiment.
Quantum Sound Quantum Sound Studios is a recording studio in Jersey City, New Jersey founded by Reggie Lucas in the 1980s. It has been under new ownership since 1994, when the name was changed to Big Blue Meenie Recording Studio.
Quantum teleportation In quantum information, quantum teleportation, or entanglement-assisted teleportation, is a technique that transfers a quantum state to an arbitrarily distant location using a distributed entangled state and the transmission of some classical information.
Quantum thermodynamics In the physical sciences, quantum thermodynamics is the study of heat and work dynamics in quantum systems. Approximately, quantum thermodynamics attempts to combine thermodynamics and quantum mechanics into a coherent whole.
Quantum tic tac toe In physics, the game of Quantum tic tac toe is a quantum generalization of tic tac toe in which the players' moves are quantum superposition of plays in the classical game. The game was invented by Allan Goff of Novatia Labs.
Quantum tomography Quantum tomography or quantum state tomography is the process of reconstructing the quantum state (density matrix) for a source of quantum systems by measurements on the systems coming from the source. To be able to uniquely identify the state, the measurements must be tomographically complete, that is the measured operators must form an operator basis on the Hilbert space of the system.
Quantitative trait locus Inheritance of quantitative traits refers to the inheritance of a phenotypic characteristic that varies in degree and can be attributed to the interactions between two or more genes and their environment (also called Polygenic inheritance). Though not necessarily genes themselves, quantitative trait loci (QTLs) are stretches of DNA that are closely linked to the genes that underlie the trait in question.
Quantities of information The mathematical theory of information is based on probability theory and statistics, and measures information with several quantities of information. The choice of logarithmic base in the following formulae determines the unit of information entropy that is used.
Quantity adjustment In economics, the concept of quantity adjustment refers to one possible result of supply and demand disequilibrium in a market, either due to or in the absence of external constraints on the market. In the textbook story, if the quantity demanded does not equal the quantity supplied in a market, price adjustment is the rule: if there is a market surplus or glut (excess supply), prices fall, ending the glut, while a shortage (excess demand) causes price rises.
Quantity surveyor A Quantity Surveyor (QS) is a professional person working within the construction industry. The role of the QS is, in general terms, to manage and control costs within construction projects and may involve the use of a range of management procedures and technical tools to achieve this goal.
Quantization Quantization is the procedure of constraining something to a discrete set of values, such as an integer, rather than a continuous set of values, such as a real number. Quantization in specific domains is discussed in:
Quantization (linguistics) In linguistics, a quantized expression is such that, whenever it is true of some entity, it is not true of any proper subparts of that entity. Example: If something is an "apple", then no proper subpart of that thing is an "apple".
Quantization (music) In digital music processing technology, quantization is the process of aligning a set of musical notes to conform to a grid. The most frequent application of quantization in this context lies within MIDI application software.
Quantization (physics) In physics, quantization is a procedure for constructing a quantum field theory starting from a classical field theory. This is a generalization of the procedure for building quantum mechanics from classical mechanics.
Quantization (signal processing) In digital signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values.
Quantization (sound processing) In signal processing, quantization is the process of approximating a continuous range of values (or a very large set of possible discrete values) by a relatively-small set of discrete symbols or integer values. This article describes aspects of quantization related to sound signals.
Quantization error When converting from an analog signal to a digital signal, error is unavoidable. An analog signal is continuous, with ideally infinite accuracy, while the digital signal's accuracy is dependent on the quantization resolution, or number of bits of the analog to digital converter.
Quantization noise Quantization noise is a noise error introduced by quantization in the analogue to digital conversion (ADC) process in telecommunication systems and signal processing. It is a rounding error between the analogue input voltage to the ADC and the output digitized value.
Quantock Lodge Quantock Lodge is a nineteenth-century mansion located near the hamlet of Aley, near the village of Over Stowey in the English county of Somerset. It was the family home of Henry Labouchere, 1st Baron Taunton, and in the 1960s was purchased by David Peaster, the headmaster of Cotham School in Bristol.
Quantrill's Raiders Quantrill's Raiders were a group of Confederate bushwhackers who followed and fought under William Clarke Quantrill, an Ohio schoolteacher who relocated to Kansas and transformed a motley group of Southern-sympathizing farmers and townsmen living behind Union lines into one of the Confederacy's most effective and electric guerrilla units. The name "Quantrill's Raiders" seems to have been attached to the group long after the war; indeed, the members would later have reunions under that name.
Quantrix Quantrix is a powerful alternative to traditional spreadsheets, based on the same novel concepts and layout as the seminal Lotus Improv. It was originally developed for NeXTSTEP and OPENSTEP by Lighthouse Design, the famous NeXT-based "virtual development company".
Quantum acoustics In physics, quantum acoustics is the study of sound under conditions such that quantum mechanical effects are germane. For most applications, classical mechanics are sufficient to accurately describe the physics of sound.
Quantum aesthetics Quantum Aesthetics is a movement that was inaugurated by Gregorio Morales at the end of the 1990s with his work “El cadaver de Balzac” or Balzac's Corpse (1998). Here he defined the objectives of the movement in the phrase “mystery and difference”.
Quantum Art Quantum Art, founded in 1998, is a web content management software company headquartered in San Francisco, California. Quantum Art helps organizations treat information, not as documents or pages, but as lightweight content applications.
Quantum biology Quantum biology is the scientific study of biological processes in terms of quantum mechanics. This nascent field is one of the first efforts to apply quantum theory to systems more macroscopic than the atomic or subatomic realms generally described by quantum theory.
Quantum bogodynamics Quantum bogodynamics is a humorous theory arising within hacker culture that characterises the universe in terms of sources of fictional fundamental particles; bogons. There are bogon sources (such as politicians, used-car salesmen, TV evangelists, and suits in general), bogon sinks (such as taxpayers and computers), and bogosity potential fields.
Quantum brain dynamics In neuroscience, quantum brain dynamics (QBD) is a proposed theory to explain the function of the brain within the framework of quantum field theory. Although there are many blank areas in understanding the brain dynamics and especially how it gives rise to conscious experience it should be noted that quantum mechanics is only conisdered by some to be capable of explaining the enigma of consciousness.
Quantum cascade laser The quantum cascade laser or QC laser is a unipolar semiconductor laser. Unlike conventional semiconductor lasers, the optical transitions occur between electric subbands rather than between the conduction band and valence bands.
Quantum cellular automata Quantum Cellular Automata is any device designed to represent data and perform computation, regardless of the physics principles it exploits and materials used to build it, must have two fundamental properties: distinguishability and conditional change of state. The latter implying the former.
Quantum circuit In quantum mechanics, a quantum circuit is a specific model for a quantum computational device. Experiments have already been carried out which can be regarded as implementing a seven-qubit quantum circuit that implements Shor's algorithm.
Quantum cloning Quantum cloning is the process that takes an arbitrary, unknown quantum state and makes an exact copy without altering the original state in any way. In Dirac notation, the process of quantum cloning is described by:
Quantum coherence Quantum coherence refers to the condition of a quantum system whose constituents are in-phase. That is, the various states that make up the combined wavefunction have a fixed phase relationship with one another, making them correlated to one another as described by quantum mechanics.
Quantum cohomology In mathematics, specifically in symplectic topology and algebraic geometry, a quantum cohomology ring is an extension of the ordinary cohomology ring of a closed symplectic manifold. It comes in two versions, called small and big; in general, the latter is more complicated and contains more information than the former.
Quantum compression The Quantum compression format is a somewhat obscure data compression method invented by a company called Cinematronics (written by an author identified as David Stafford). Rights to it were purchased at some point by Microsoft, and Quantum is one of the possible compression methods in a CAB archive.
Quantum computer A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, the data is measured by qubits.
Quantum correlation In Bell test experiments the term quantum correlation has come to mean the expectation value of the product of the outcomes on the two sides. In the paper that inspired the Bell tests -- John Bell's of 1964 -- it was assumed that the outcomes A and B could each only take one of two values, -1 or +1.
Quantum cosmology In theoretical physics, quantum cosmology is a young field attempting to study the effect of quantum mechanics on the earliest moments of the universe after the Big Bang. Despite many attempts, the field remains a rather speculative branch of quantum gravity.
Quantum cryptography Quantum cryptography uses quantum mechanics for secure communications. Unlike traditional cryptography, which employs classical mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is based on the quantum physics of information.
Quantum Critical Point A Quantum critical point is a special class of continuous phase transition that takes place at the absolute zero of temperature, typically in a material where the phase transition temperature has been driven to zero by the application of a pressure, field or through doping.
Quantum damped harmonic oscillator The quantum damped harmonic oscillator combines concepts from the classical damped harmonic oscillator and the quantum harmonic oscillator. An overview of the quantum damped harmonic oscillator can be found in a paper by Depp The Quantum Damped Harmonic Oscillator.
Quantum darwinism Quantum darwinism is a theory explaining the emergence of the classical world from the quantum world as due to a process of Darwinian selection. It is proposed by Wojciech Zurek and a group of collaborators including Ollivier, Poulin, Paz and Blume-Kohout.
Quantum decoherence In quantum mechanics, quantum decoherence is the mechanism by which quantum systems interact with their environments to exhibit probabilistically additive behavior - a feature of classical physics - and give the appearance of wavefunction collapse. Decoherence occurs when a system interacts with its environment, or any complex external system, in such a thermodynamically irreversible way that ensures different elements in the quantum superposition of the system+environment's wavefunction can no longer interfere with each other.
Quantum degeneracy A quantum degeneracy is a quantum eigenvalue which has more than one linearly independent eigenvector. For instance, the quantum degeneracy of the 1s^1 electron configuration within a hydrogen atom is two in the absence of an external magnetic field, because there are two linearly independent 1s spin-orbitals with the same total energy.
Quantum dot A quantum dot is a semiconductor nanostructure that confines the motion of conduction band electrons, valence band holes, or excitons (pairs of conduction band electrons and valence band holes) in all three spatial directions. The confinement can be due to electrostatic potentials (generated by external electrodes, doping, strain, impurities), due to the presence of an interface between different semiconductor materials (e.
Quantum dot laser A quantum dot laser succeeds in minimizing temperature-sensitive output fluctuations, something not possible with previous semiconductor lasers. Fujitsu and the University of Tokyo have developed a 10 Gbit/s quantum dot laser not affected by temperature, for use in optical data communications and optical networks.
Quantum efficiency Quantum efficiency (QE) is a quantity defined for a photosensitive device such as photographic film or a charge-coupled device (CCD) as the percentage of photons hitting the photoreactive surface that will produce an electron–hole pair. It is an accurate measurement of the device's sensitivity.
Quantum electrodynamics Quantum electrodynamics (QED) is a relativistic quantum field theory of electromagnetism. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange by photons, whether the interaction is between light and matter or between two charged particles.
Quantum electrochemistry The scientific school of Quantum electrochemistry began to form in the 1960s under Revaz Dogonadze. Generally speaking, the field is comprised of the notions arising in electrodynamics, quantum mechanics, and electrochemistry; and so is studied by a very large array of different professional researchers.
Quantum entanglement Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated. This leads to correlations between observable physical properties of the systems.
Quantum eraser experiment In physics, the quantum eraser experiment is a double-slit experiment that demonstrates several laws of Quantum Mechanics, including wave-particle duality which seeks to explain certain wave and particle properties of matter, complementarity and the Copenhagen interpretation which outline the idea that, in QM, to gain an accurate measurement of one aspect of certain experimental subjects is to lose precision in its counterpart (much like attempting to view both sides of a coin at once). The experiment also utilizes a special crystal for its ability to produce photon pairs from a single photon and the use of an interferometer to explore the wave-like nature of an object.
Quantum error correction Quantum error correction is for use in quantum computing to protect quantum information from errors due to decoherence and other quantum noise. Quantum error correction is essential if one is to achieve fault-tolerant quantum computation that can deal not just with noise on stored quantum information, but also with faulty quantum gates, faulty quantum preparation, and faulty measurements.
Quantum evolution Quantum evolution was a component of George Gaylord Simpson's (1902-1984) multi-tempoed theory of evolutionary change. According to Simpson (1944), some lineages in the fossil record evolved with extraordinary slowness, others more rapidly.
Quantum Effect Devices Quantum Effect Devices was a company originally named Quantum Effect Design, incorporated in 1991. The three founders, Tom Riordan, Earl Killian and Ray Kunita were senior managers at MIPS Computer Systems Inc..
Quantum Efficiency of a solar cell Quantum efficiency (QE) is the ratio of the number of charge carriers collected by the solar cell to the number of photons of a given energy shining on the solar cell. QE therefore relates to the response of a solar cell to the various wavelengths in the spectrum of light shining on the cell.
Quantum field theory Quantum field theory (QFT) is the quantum theory of fields. It provides a theoretical framework, widely used in particle physics and condensed matter physics, in which to formulate consistent quantum theories of many-particle systems, especially in situations where particles may be created and destroyed.
Quantum field theory in curved spacetime Quantum field theory in curved spacetimes is an extension of standard quantum field theory to curved spacetimes. A general prediction of this theory is that particles can be created in strong gravitational fields.
Quantum finite automata In quantum computing, quantum finite automata or QFA are a quantum analog of probabilistic automata. They are related to quantum computers in a similar fashion as finite automata are related to Turing machines.
Quantum flavordynamics In quantum mechanics, quantum flavordynamics (or "flavourdynamics") is a mathematical model used to describe the interaction of flavored particles (weak force) through the exchange of intermediate vector bosons, but the term is rarely used by practicing particle physicists.
Quantum flux parametron Invented by Eiichi Goto at the University of Tokyo, the Quantum Flux Parametron (QFP) is an improvement over his earlier parametron based digital logic technology. Unlike its predecessor, QFP uses superconducting Josephson junctions on integrated circuits to improve speed and energy efficiency enormously.
Quantum foam Quantum foam, also referred to as spacetime foam, is a concept in quantum mechanics, devised by John Wheeler in 1955. The foam is a qualitative description of the turbulence that the phenomenon creates at extremely small distances of the order of the Planck length.
Quantum Fourier transform The quantum Fourier transform is the discrete Fourier transform with a particular decomposition into a product of simpler unitary matrices. Using this decomposition, the discrete Fourier transform can be implemented as a quantum circuit consisting of Hadamard gates and controlled phase shift gates.
Quantum geometry In theoretical physics, quantum geometry is the set of new mathematical concepts generalizing the concepts of geometry whose understanding is necessary to describe the physical phenomena at very short distance scales (comparable to Planck length). At these distances, quantum mechanics has a profound effect on physics.
Quantum gravity Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature, with general relativity, the theory of the fourth fundamental force: gravity. The ultimate goal of some is a unified framework for all fundamental forces—a "theory of everything".
Quantum gravity epoch In physical cosmology, the quantum gravity epoch is the first era in the history of the Universe according to the standard Big Bang cosmology. In this era, the effects of quantum gravity such as fluctuating topology of space are commonplace.
Quantum GIS Quantum GIS (often abbreviated to QGIS) is an open source GIS (mapping) application which is similar to commercial mapping packages. Because it is distributed as an opensource application under the GNU distribution license, Quantum GIS can be reprogrammed to perform different or more specialist tasks.
Quantum harmonic oscillator The quantum harmonic oscillator is the quantum mechanical analogue of the classical harmonic oscillator. It is one of the most important model systems in quantum mechanics because, as in classical mechanics, a wide variety of physical situations can be reduced to it either exactly or approximately.
Quantum heterostructure Quantum heterostructure is a heterostructure in a substrate (usually a semiconductor material), with size restricting the movements of the charge carriers and forcing them into a quantum confinement, leading to formation of a set of discrete energy levels the carriers can exist at. Quantum heterostructures have sharper density of states than structures of more conventional sizes.
Quantum history In some physics theories, choosing a 3-geometry via spin network and 4-geometry via spin foam, any superposition of spin networks is called a kinematical state and any superposition of spin foams is called a quantum history.
Quantum hydrodynamics Quantum hydrodynamics is more than the study of superfluidity. Some of the main subjects in quantum hydrodynamics are quantum turbulence, quantized vortices, first, second and third sound, and quantum solvents.
Quantum Hall effect The quantum Hall effect is a quantum-mechanical version of the Hall effect, observed in two-dimensional electron systems subjected to low temperatures and strong magnetic fields, in which the Hall conductance Ď takes on the quantized values
Quantum chemistry Quantum chemistry is a branch of theoretical chemistry, which applies quantum mechanics and quantum field theory to address issues and problems in chemistry. The description of the electronic behavior of atoms and molecules as pertaining to their reactivity is one of the applications of quantum chemistry.
Quantum chromodynamics Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (colour force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion). QCD is a quantum field theory of a special kind called a non-abelian gauge theory.
Quantum immortality Quantum immortality is the controversial metaphysical speculation deriving from the quantum suicide thought experiment that states the many-worlds interpretation of quantum mechanics implies that conscious beings are immortal.
Quantum indeterminacy Quantum indeterminacy is the apparent necessary incompleteness in the description of a physical system, that has become one of the characteristics of the standard description of quantum physics. Prior to quantum physics, it was thought that (a) a physical system had a determinate state which uniquely determined all the values of its measurable properties, and conversely (b) the values of its measurable properties uniquely determined the state.
Quantum information In quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-state quantum system.
Quantum information science Quantum information science concerns information science that depends on quantum effects in physics. It includes theoretical issues in computational models as well as more experimental topics in quantum physics including what can and cannot be done with quantum information.
Quantum level Quantum levels are fixed levels with a logarithmic, descending quantum pattern in the visible spectrum of light that can be observed through a spectrometer while looking at intense flows of electricity through the various halides on the periodic table in a vacuum tube. They also have some use in chemistry when dealing with the movement of electrons to different orbital levels around the atom and the energy levels involved in such actions.
Quantum logic In mathematical physics and quantum mechanics, quantum logic is an operator algebraic system for constructing and manipulating logical combinations of quantum mechanical events. It can be regarded as a kind of propositional logic suitable for understanding the apparent anomalies regarding quantum measurement, most notably those concerning composition of measurement operations of complementary variables.
Quantum Link Reloaded Quantum Link Reloaded is a re-implementation of the original Quantum Link (Q-Link) online service for the Commodore 64 home computer system. The formal introduction of Quantum Link Reloaded was held on the 20th Anniversary of the introduction of Quantum Link, November 5, 2005.
Quantum mechanical Bell test prediction In physics, the quantum mechanical Bell test prediction is the prediction that quantum mechanics would give for the correlation probabilities for a set of measurements performed on a quantum entangled state. An important outcome of this prediction is that it violates the Bell inequality, which, as a result, has serious implications for the interpretation of quantum mechanics.
Quantum mechanics Quantum mechanics is a fundamental branch of theoretical physics with wide applications in experimental physics that replaces classical mechanics and classical electromagnetism at the atomic and subatomic levels. It is the underlying mathematical framework of many fields of physics and chemistry, including condensed matter physics, solid-state physics, atomic physics, molecular physics, computational chemistry, quantum chemistry, particle physics, and nuclear physics.
Quantum mechanics, philosophy and controversy Quantum mechanics has had a profound effect on philosophy. Determinism is a philosophical view that the universe is governed by determinism if given a specific state of the universe at a specific time, the future state of the universe is fixed as a matter of natural law.
Quantum metrology Quantum metrology is the study of making high resolution measurements of parameters using quantum theory to describe the physical systems. This can give rise to measurements which give better precision than the same measurement performed in a classical framework.
Quantum mind The quantum mind theory is founded on the premise that quantum theory is necessary to fully understand the mind and brain, particularly concerning an explanation of consciousness. This is considered a minority opinion in science, although it does have the support of the well-known mathematical physicist Sir Roger Penrose.
Quantum mirage In physics, a quantum mirage is a peculiar result in quantum chaos. Every system of quantum dynamical billiards will exhibit an effect called scarring, where the quantum probability density shows traces of the paths a classical billiard ball would take.
Quantum mutual information In quantum information theory, quantum mutual information, or von Neumann mutual information, is a measure of correlation between subsystems of quantum state. It is the quantum mechanical analog of Shannon mutual information.
Quantum Monte Carlo Quantum Monte Carlo is a large class of computer algorithms that simulate quantum systems with the idea of solving the many-body problem. They use, in one way or another, the Monte Carlo method to handle the many dimensional integrals that arise.
Quantum network The idea of a quantum network emerged after successful experiments on quantum teleportation. When two companies (one from Switzerland, 'idQuantique', and another from the USA, 'MagiQTech') released practcal communication devices based upon the rules of quantum mechanics, the need for a secure network capable of utilizing quantum principles was realized.
Quantum operation In quantum mechanics, a quantum operation is a mathematical formalism used to describe a broad class of transformations that a quantum mechanical system can undergo. This formalism describes not only time evolution or symmetry transformations of isolated systems, but also transient interactions with an environment for purposes of measurement.
Quantum phase transition In physics, a quantum phase transition (QPT) is a phase transition between different quantum phases (phases of matter at zero temperature). Contrary to classical phase transitions, quantum phase transitions can be only be accessed by varying a physical parameter - such as magnetic field or pressure - at absolute zero temperature.
Quantum probability Quantum probability was developed in the 1980's as a noncommutative analog of the Kolmogorovian stochastic processes theory. One of its aims is to clarify the probabilistic mathematical foundations of quantum theory and its statistical interpretation.
Quantum programming language Quantum Programming Languages are programming languages that can be used to write programs for quantum computers. Generally, such languages attempt to provide high-level constructs for expressing quantum algorithms.
Quantum Philosophy (book) Quantum Philosophy is a book by the physicist Roland Omnès, in which he aims to show the non-specialist reader how modern developments in quantum mechanics allow the recovery of our common sense view of the world.
Quantum satis Quantum Satis (abbreviation qs or QS) is a Latin term meaning The amount which is needed. It has its origins as a quantity specification in medicine and pharmacology, but is also used in the same function in food regulations and food safety laws in the European Community.
Quantum singularity (fiction) In science fiction, the term quantum singularity is used to refer to many different phenomena, which often approximately resemble a gravitational singularity in the scientific sense in that they are massive, localized distortions of space and time. The name invokes one of the most fundamental problems remaining in modern physics: the difficulty in merging Einstein's Theory of Relativity (which includes singularities within its models of black holes) and quantum mechanics.
Quantum solid In physics, a quantum solid is a type of solid that is "intrinsically restless", in the sense that atoms continuously vibrate about their position and exchange places even at the absolute zero of temperature. The archetypal quantum solid is low density solid helium.
Quantum solvent A quantum solvent is essentially a superfluid (aka a quantum liquid) used to dissolve another chemical species. Any superfluid can theoretically act as a quantum solvent, however in practice the only viable superfluid medium that can currently be used is helium-4, and it has been successfully accomplished in controlled conditions.
Quantum sort A quantum sort is any sorting algorithm that runs on a quantum computer. Such an algorithm could at best be linearly faster than any existing sort algorithm (if based on comparisons like classical algorithms), but no such algorithm has actually been implemented.
Quantum statistical mechanics Quantum statistical mechanics is the study of statistical ensembles of quantum mechanical systems. A statistical ensemble is described by a density operator S, which is a non-negative, self-adjoint, trace-class operator of trace 1 on the Hilbert space H describing the quantum system.
Quantum suicide In quantum mechanics, quantum suicide is a thought experiment which was independently proposed in 1987 by Hans Moravec and in 1988 by Bruno Marchal, and further developed by Max Tegmark in 1998Tegmark, Max The Interpretation of Quantum Mechanics: Many Worlds or Many Words?, 1998, that attempts to distinguish between the Copenhagen interpretation of quantum mechanics and the Everett many-worlds interpretation by means of a variation of the Schrödinger's cat experiment.
Quantum Sound Quantum Sound Studios is a recording studio in Jersey City, New Jersey founded by Reggie Lucas in the 1980s. It has been under new ownership since 1994, when the name was changed to Big Blue Meenie Recording Studio.
Quantum teleportation In quantum information, quantum teleportation, or entanglement-assisted teleportation, is a technique that transfers a quantum state to an arbitrarily distant location using a distributed entangled state and the transmission of some classical information.
Quantum thermodynamics In the physical sciences, quantum thermodynamics is the study of heat and work dynamics in quantum systems. Approximately, quantum thermodynamics attempts to combine thermodynamics and quantum mechanics into a coherent whole.
Quantum tic tac toe In physics, the game of Quantum tic tac toe is a quantum generalization of tic tac toe in which the players' moves are quantum superposition of plays in the classical game. The game was invented by Allan Goff of Novatia Labs.
Quantum tomography Quantum tomography or quantum state tomography is the process of reconstructing the quantum state (density matrix) for a source of quantum systems by measurements on the systems coming from the source. To be able to uniquely identify the state, the measurements must be tomographically complete, that is the measured operators must form an operator basis on the Hilbert space of the system.
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