
	Where results make sense

Topic: Quantum measurement

Related Topics

quantum computers

quantum field theory

quantum physics

quantum gravity

quantum electrodynamics

Quantum Leap

quantum entanglement

quantum theory

loop quantum gravity

quantum chromodynamics

quantum chemistry

In the News (Tue 22 Dec 09)

Northern Trust

Marvin Harrison

Peter Chernin

Gary Locke

Match Play

Penelope Cruz

Mickey Rourke

AR Rahman

Danny Boyle

Hugh Jackman

	Measurement in quantum mechanics FAQ
		Quantum entanglement refers to the way observations of two particles are correlated after the particles interact.
		The quantum measurement process happens ``when'' the transaction (OW sent - CW received - standing wave formed with probability \\Psi \\Psi*) is finished - and this happens over a space-time interval; thus, one cannot point to a time of collapse, only to an interval of collapse (consistent with relativity).
		If quantum theory is true, there are cases in which the results of the measurements A will depend on the setting of the knob b and/or the results of the measurements in B will depend on the setting of the knob a.[1] It is logically possible to deny CFD and thus to avoid Eberhard's proof.
	www.faqs.org /faqs/physics-faq/measurement-in-qm (4583 words)

	Measurement in Quantum Theory (Stanford Encyclopedia of Philosophy)
		The problem of measurement in quantum mechanics arises out of the fact that several principles of the theory appear to be in conflict.
		In particular, the dynamic principles of quantum mechanics seem to be in conflict with the postulate of collapse.
		The second stage of the measurement, with its radical, non-linear discontinuities, was from its introduction the source of many of the philosophical difficulties that plagued QM, including what von Neumann referred to as its "peculiar dual nature" (417).
	plato.stanford.edu /entries/qt-measurement (3942 words)

	Quantum Future Abstracts
		The standard formalism of quantum theory is enhanced and definite meaning is given to the concepts of experiment, measurement and event.
		Quantum jumps are shown, in the simplest, homogeneous case, to be identical to those in the early spontaneous localization model of Ghirardi, Rimini and Weber (GRW).
		A model interaction between a two-state quantum system and a classical switching device is analysed and shown to lead to the quantum Zeno effect for large values of the coupling costant kappa.
	quantumfuture.net /quantum_future/qf-abs.htm (1186 words)

	Quantum logic Information
		In mathematical physics and quantum mechanics, quantum logic 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 logic has been proposed as the correct logic for propositional inference generally, most notably by the philosopher Hilary Putnam, at least at one point in his career.
		Quantum logic can be stretched to account for some kinds of measurement processes corresponding to answering yes-no questions about the state of a quantum system.
	www.bookrags.com /wiki/Quantum_logic (2730 words)

	CH: Questions and Answers
		Consistent histories is standard quantum mechanics presented in a coherent fashion with the ambiguities and lack of clarity found in the usual textbook presentations replaced with a clear set of logical rules and principles for reasoning about a quantum system.
		Quantum dynamical processes are inherently stochastic, and the probabilities can be calculated using a generalization of the rule originally introduced by Born.
		The analysis carried out by EPR was based on the theory of quantum measurements available at that time, and their conclusion, that there was something unsatisfactory about the way in which quantum mechanics had been formulated, was basically correct, even if they themselves were unable to come up with a better version.
	quantum.phys.cmu.edu /CHS/quest.html (1959 words)

	A Foundational Principle for Quantum Mechanics* (Site not responding. Last check: 2007-10-20)
		In the case of quantum mechanics, an essential ingredient at the basic level is the interpretation of the absolute square of the amplitude as a probability or probability density.
		Quantum mechanics does not provide any reason why in a specific run of the experiment the specific result observed is actually obtained.
		If, without loss of generality, we consider measurement of spin along the z-axis, then proposition 1 could simply be a statement about the spin of particle 1 along that axis, and proposition 2 could be a statement about the spin of particle 2 along that axis.
	www.quantum.at /zeilinger/found.htm (3118 words)

	News - July-August 2004
		The photons interacted with the atoms in the cloud and became polarized, and the measurement of the photons’; polarization indicated the z component of the cloud’s spin orientation.
		To measure the coherent spin-state between the two quantum dots, and to link it to conventional circuitry, the device uses a second spin-related quantum phenomenon called the Kondo effect.
		In an isolated quantum dot, conductance through the dot is low because the energy level inside it is not matched to the energy level of the conduction electrons outside.
	www.aip.org /tip/INPHFA/vol-10/iss-4/p8.html (2245 words)

	Measurement in quantum mechanics - Wikipedia, the free encyclopedia
		Studying these processes provides considerable insight into the measurement problem by avoiding the arbitrary boundary between the quantum and classical worlds, though it does not explain the presence of randomness in the choice of final eigenstate.
		The initially isolated quantum system then appears to "collapse." Interpreting the second system as a measurement apparatus, as in the von Neumann scheme, shows that no consciousness or self-awareness is necessary for collapse of the first system.
		The question of whether a measurement actually determines the state, is deeply related to the Wavefunction collapse.
	en.wikipedia.org /wiki/Quantum_measurement (1846 words)

	Historical Notes: Quantum measurement
		And a major apparent problem was that if everything - including the measuring device - is supposed to be treated as part of the same quantum system, then all of it must follow the rules for pure quantum processes, which do not explicitly include any reduction of the kind supposed to occur in observations.
		And in the context of standard quantum theory this means that somehow all the probability amplitudes associated with the measuring device must in effect be concentrated in specific outcomes - with no significant interference between different outcomes.
		As suggested by the main text, the details in the quantum measurement case are slightly more complicated - since to represent multiple outcomes measuring devices typically have to have the analogs of multiple equilibrium states.
	www.wolframscience.com /reference/notes/1062b (1427 words)

	Quantum Measurement
		This book is an up-to-date introduction to the quantum theory of measurement, a fast developing field of intense current interest to scientists and engineers for its potential high-technology applications.
		It is also a subject of importance to students for its central role in the foundations of quantum mechanics.
		Quantum measurements is now central to many ultra-high technology developments, such as squeezed light, single atom traps, and searches for gravitational radiation.
	www.xmlwriter.net /books/viewbook/Quantum_Measurement-0521484138.html (335 words)

	Quantum Reality
		Bohr's view was that measuring devices are "essentially classical" in the sense that (1) they deal with classical concepts such as position, momentum etc. and (2) the examination of their macroscopic structure determines what they measure.
		Once a measurement is made at A, a new waveform is associate with observer A which indicates the new measured value of momenta/spin, AND the values of momenta/spin of the particle at B implied by conservation laws.
		The problem with applying the inequality to Quantum Mechanics is that measuring one quantity may affect the measurement of another - it is generally not possible to measure the initial values of both A and B for a single particle.
	www.quantum.bowmain.com /Quantum_Reality.htm (13033 words)

	Slashdot \| Breakthrough for Quantum Measurement
		However, quantum computers are designed with this in mind; reading the output destroys any quantum properties it may have, but a computation can be repeated many times to get an idea of what uncertainty was present in the output.
		Quantum Computing may very well not be immediately useful in many traditional computation tasks ("While this value is true then do that") but it will open up whole new ways of tackling processes that are time consuming with today's methods ("do any of these things give us this, that, or something in between?").
		Another example, measuring the state of a qubit (whether it is a zero or a one) destroys the relative phase between the zero and the one.
	rss.slashdot.org /Slashdot/slashdot?m=2028 (3779 words)

	Quantum Measurement - Cambridge University Press
		This book is an up-to-date introduction to the quantum theory of measurement, a fast developing field of intense current interest to scientists and engineers for its potential high technology applications.
		It is also a subject of importance to students for its central role in the foundations of quantum mechanics.
		Quantum measurement is now central to many ultra-high technology developments, such as squeezed light, single atom traps, and searches for gravitational radiation.
	www.cambridge.org /catalogue/catalogue.asp?isbn=052141928X (271 words)

	Quantum Measurement Frames (Site not responding. Last check: 2007-10-20)
		Since his quantum reference frames are tied to position and momentum, he is forced to give a fairly weak account with respect to other measurements.
		During a position measurement, the reference frame is incapable of defining momentum, due to the acceleration of the reference frame.
		So, for example, if we measure the x-spin of particle 1 to be up, we can infer that the x-spin of particle 2 is down, whereas if we measure the z-spin of particle 1 to be down, we can infer that the z-spin of particle 2 is up.
	thm.askee.net /articles/frames (8196 words)

	Quantum Measurement (Site not responding. Last check: 2007-10-20)
		Some quantity such as position or momentum is always indefinite on a quantum system; and if an indefinite quantity is measured, the macroscopic state of the measuring apparatus that is supposed to record the outcome instead becomes indefinite itself.
		In Quantum Measurement, editors Richard A. Healey and Geoffrey Hellman marshal the resources of leading physicists and philosophers of science, skillfully joining their insights and ingenuity to yield some of the most innovative and altogether promising thought to date on this enigmatic issue.
		What emerges from this careful synthesis is a theoretically powerful and energetic new approach to the measurement dilemma, one that furthers our conceptual understanding of the fundamental interconnections between micro- and macroscopic systems, and that strives, ultimately, to describe and define within a unified quantum mechanical framework the breadth of our physical reality.
	www.upress.umn.edu /Books/H/healey_quantum.html (329 words)

	Details for Open Source Physics: Quantum Mechanical Measurement
		This set of quantum mechanics java applets, part of the Open Source Physics project, provides simulations that demonstrate the effect of measurement on the time-dependence of quantum states.
		Exercises are available that demonstrate the results of measurement of energy, position, and momentum on states in potential wells (square well, harmonic oscillator, asymmetric well, etc).
		The multiple measurements can be made on a single state or single measurements can be made on identically prepared elements of an ensemble.
	www.compadre.org /Quantum/items/detail.cfm?ID=3943 (318 words)

	THEORETICAL PHYSICS: ON QUANTUM MEASUREMENT LIMITS
		Second, every measurement apparatus is itself a quantum system: As a result, the uncertainty relations together with other quantum constraints on the speed of evolution [such as the Margolus-Levitin theorem [2]] impose limits on how accurately we can measure quantities, given the amount of physical resources, such as energy, at hand to perform the measurement.
		The research on quantum-enhanced measurements was spawned by the invention of such techniques [3] and by the birth of more rigorous treatments of quantum measurements.
		Typical examples are the environment-induced noise from vacuum fluctuations (the so-called "shot noise") that affects the measurement of the electromagnetic field amplitude, and the dynamically induced noise in the position measurement of a free mass (the so-called "standard quantum limit").
	scienceweek.com /2005/sc050114-6.htm (2201 words)

	On the End of a Quantum Mechanical Romance
		That is, given that the cosmos is in a pure quantum state, we cannot separate off the billiard ball and be left with a billiard ball in a pure state and a rest-of-the-cosmos in a pure state.
		Quantum mechanics may be very important for understanding why extremely low level structures in brains and the like work as they do, but interactive decoherence precludes its having anything to say about larger scale properties of such structures or--very probably--of minds.
		If we start from the standpoint of the traditional quantum measurement theory of more than the last half century, it might seem at first that 'adding in' the proposition that a decohered system is actually objectively in an eigenstate before a conscious observation is made is unfairly putting consciousness on the dole.
	psyche.csse.monash.edu.au /v2/psyche-2-19-mulhauser.html (6053 words)

	Quantum Watches
		Quantum was established in 1995 with the experience of 21years.
		The main goal of Quantum is to combine the person with their Quantum watches.
		Quantum Diving Watches, built to match up to the most demanding scuba diving challenge, stand out with demanding time-measurement features and solid components.
	www.outdoorgb.com /c/quantum_watches (245 words)

	CNR-->Monografia: Time's arrows, quantum measurement and superluminal behavior
		quantum optics and in atomic physics, and are at the forefront of recent experimental efforts in fundamental issues.
		The conference "Time's Arrows, Quantum Measurement and Superluminal Behavior", was held at the Istituto Italiano per gli Studi Filosofici in Napoli (October 3-5, 2000), and treated the topics mentioned above.
		The Directors of the conference are grateful to Gerardo Marotta and Antonio Gargano, the President and the Director, respectively, ofthe Istutito Italiano per gli Studi Filosofici, far the hospitality of their Institute and far the support given to the conference.
	www.cnr.it /sitocnr/Iservizi/Pubblicazioni/Monografie/IngeArch_MatFis/MatematicaFisica/Time/Time_prefaz.html (496 words)

	Consciousness and Quantum Measurement
		This quantum potential is non-local and the effect of it continues even in empty space, so, for example, Newton's first law that objects travel in straight lines in the absence of any external forces no longer applies.
		As Henry Stapp (1989) has already pointed out, the measurement problem is "bypassed" by assuming that the quantum potential forces the particle into one channel, although the other channels of the wave function remain empty.
		In the phenomenon of quantum tunneling, the time taken by a quantum object while going through the tunnel can be measured, and such measurements are now revealing a compelling case of faster-than-light propagation (Chiao).
	www.meta-religion.com /Physics/Consciousness/consciousness_and_quantum_measur.htm (1580 words)

	Completely Mixing Quantum Open Systems and Quantum Fractals
		Summary: Departing from classical concepts of ergodic theory, formulated in terms of probability densities, measures describing the chaotic behavior and the loss of information in quantum open systems are proposed.
		Simultaneous measurement of four noncommuting spin components is shown to lead to a chaotic jump on
		The model is purely theoretical at this stage, and experimental confirmation of the chaotic behavior of measuring instruments during simultaneous continuous measurement of several noncommuting quantum observables would constitute a quantitative verification of
	www.quantumfuture.net /arkadiusz-jadczyk/papers/qifs.htm (213 words)

	Quantum Measurement of a Single System
		With new technologies permitting the observation and manipulation of single quantum systems, the quantum theory of measurement is fast becoming a subject of experimental investigation in laboratories worldwide.
		It establishes the quantum theoretical limits to information obtained in the measurement of a single system on the quantum wavefunction of the system, the time evolution of the quantum observables associated with the system, and the classical potentials or forces which shape this time evolution.
		Suitable for professionals, students, or readers with a general interest in quantum mechanics, the book features recent formulations as well as humorous illustrations of the basic concepts of quantum measurement.
	www.xmlwriter.net /books/viewbook/Quantum_Measurement_of_a_Single_System-0471283088.html (343 words)

	Breakthrough for quantum measurement (November 2005) - News - PhysicsWeb
		The methods developed by the two teams could be used to measure the state of quantum bits in a quantum computer without disturbing the state.
		Based on these measurements, the team was able to show that the device behaved like a quantum capacitor.
		The effect could be used to read out quantum bits (qubits) in a reliable way because the quantum capacitance of the excited state of the qubit has the opposite sign to the ground state.
	physicsweb.org /articles/news/9/11/13/1 (494 words)

	Details for Open Source Physics: Quantum Mechanical Measurement
		This set of quantum mechanics java applets, part of the Open Source Physics project, provides simulations that demonstrate the effect of measurement on the time-dependence of quantum states.
		Exercises are available that demonstrate the results of measurement of energy, position, and momentum on states in potential wells (square well, harmonic oscillator, asymmetric well, etc).
		The multiple measurements can be made on a single state or single measurements can be made on identically prepared elements of an ensemble.
	www.quantumexchange.net /items/detail.cfm?ID=3943 (277 words)

Try your search on: Qwika (all wikis)