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Topic: Quantum superposition


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In the News (Fri 24 May 19)

  
  Quantum superposition - Wikipedia, the free encyclopedia
Quantum superposition is the application of the superposition principle to quantum mechanics.
The superposition principle is the addition of the amplitudes of waves from interference.
In quantum mechanics it is the amplitudes of wavefunctions, or state vectors, that add.
en.wikipedia.org /wiki/Quantum_superposition   (270 words)

  
 Quantum Consciousness . Stuart Hameroff
The boundary between the quantum and classical worlds is unclear, and the transition between the two is commonly described as quantum state reduction, collapse of the wave function, or decoherence.
Early quantum experiments led to the conclusion that quantum superpositions persisted until measured or observed by a conscious observer, that "consciousness collapsed the wave function".
The theory of decoherence reconciles the Copenhagen interpretation with quantum superpositions in the absence of measurement or conscious observation.
www.quantumconsciousness.org /overview.html   (2321 words)

  
 Quantum Superposition
superposition principle: The general idea that, when a number of influences are acting on a system, the total influence on that system is merely the sum of the individual influences; that is, influences governed by the superposition principle add linearly.
The Quantum Conundrum, or the Whorf and Wolf ot the Universe
Quantum theory moves beyond demanding that the photon exist as either a particle or a wave exclusively, to a position of describing an object as having both particle and wave qualities.
www.geocities.com /Athens/Acropolis/2606/superpos.htm   (2223 words)

  
 Time
Mass in quantum superposition (mass separated from itself) is simultaneous spacetime curvature in opposite directions, a separation, or bubble in spacetime.
The instability is inherent in the properties of spacetime geometry (quantum gravity) and constitutes an objective threshold for an isolated quantum state reduction, hence "objective reduction (OR)".
The magnitude E is related to the gravitational self-energy of the superposition and may be calculated from the amount of mass "separated from itself" and distance of separation.
www.quantumconsciousness.org /Time.htm   (3847 words)

  
 Quantum Consciousness
Quantum level dipole oscillations within hydrophobic pockets were proposed by Frohlich (1968) to regulate protein conformation, and Conrad (1994) suggested proteins utilize quantum superposition of various possible conformations before one is selected.
Feasibility of quantum coherence in the internal cell environment is supported by the observation that quantum spins from biochemical radical pairs which become separated retain their correlation in cytoplasm (Walleczek, 1995).
Rather than trapped ions or nuclear spins, quantum superposition is proposed to occur at the level of conformational states of tubulins, and the role of pulsed transitions played by coherent Frhlich excitations.
www.quantumconsciousness.org /penrose-hameroff/quantumcomputation.html   (9122 words)

  
 Relational Quantum Mechanics
The difficulty in the interpretation of quantum mechanics derives from the fact that the theory was first constructed for describing microscopic systems (atoms, electrons, photons) and the way these interact with macroscopic apparatuses built to measure their properties.
Quantum events only happen in interactions between systems, and the fact that a quantum event has happened is only true with respect to the systems involved in the interaction.
Relational interpretations of quantum mechanics propose a solution to the interpretational difficulties of quantum theory based on the idea of weakening the notions of the state of a system, event, and the idea that a system, at a certain time, may just have a certain property.
plato.stanford.edu /entries/qm-relational   (5152 words)

  
 Here, There and Everywhere: A Quantum State of Mind
The two quantum states -- clockwise versus counterclockwise current or the alive versus dead cat -- correspond to the child's being on the left- or right-hand side of the swing's arc.
In quantum mechanics, however, the mere act of looking, whether the child is seen or not, disturbs the possibilities because, as Dr. Leggett explains, the superposition has been destroyed.
In essence, in a quantum mechanical world, not seeing the child on the right-hand side resets the child's swing to the top of left side of the arc, altering the probabilities of where the child will be seen later.
www.amherst.edu /~jrfriedman/NYTimes/071100sci-quantum-mechanics.html   (1357 words)

  
 The Initialization Problem in Quantum Computing
The paper also presents general observations on the nonlocal nature of quantum errors and the expected performance of the recently proposed quantum error-correction codes that are based on the assumption that the errors are either bit-flip or phase-flip or both.
Quantum errors, on the other hand, perturb the information bits, in a nonlocal sense, to a superposition of many states so the concept of controlling all errors by using a higher dimensional codeword space cannot be directly applied.
According to the positivist understanding of quantum mechanics, it is essential to speak from the point of view of the observer and not ask about any intrinsic information in a quantum state[6].
www.ece.lsu.edu /kak/pubs/inf4   (3811 words)

  
 An introduction to Quantum Computing
The simulation of a quantum computer on a classical one is a computationally hard problem because the correlations among quantum bits are qualitatively different from correlations among classical bits, as first explained by John Bell.
The answer is primarily those errors that arise as a direct result of decoherence, or the tendency of a quantum computer to decay from a given quantum state into an incoherent state as it interacts, or entangles, with the state of the environment.
Quantum mechanics tells us that directly measuring the state of a qubit invariably destroys the superposition of states in which it exists, forcing it to become either a 0 or 1.
www.cs.caltech.edu /~westside/quantum-intro.html   (3038 words)

  
 Fundamentals of quantum information (March 1998) - Physics World - PhysicsWeb
A well known example of quantum superposition is the double-slit experiment in which a beam of particles passes through a double slit and forms a wave-like interference pattern on a screen on the far side.
A necessary condition for quantum interference is that the experiment must be performed in such a way that there is no way of knowing, not even in principle, which of the two slits the particle passed through on its way to the screen.
Quantum dense coding was the first experimental demonstration of the basic concepts of quantum communication.
physicsweb.org /articles/world/11/3/9   (3302 words)

  
 Problem with Quantum Mind Theory
The basic argument is that temperatures in the brain are too high for atoms, photons, or electrons to remain in a super position of states for longer than 10**-13 (12 zeros after the decimal) seconds.
Quantum consciousness aficionados suspect that the analogy might be more than a coincidence.
Quantum physicists, however, largely ignored it as too speculative to be worth testing with numerical calculations.
www.sustainedaction.org /Explorations/problem_with_quantum_mind_theory.htm   (950 words)

  
 PhilSci Archive - Quantum superposition principle justified in a new non-Aristotelian finitary logic   (Site not responding. Last check: 2007-10-21)
Quantum superposition principle justified in a new non-Aristotelian finitary logic
Here T* is an axiomatic NAFL theory that, like T, resides in the human mind and acts as the "truth-maker" for (a model of) T. Quantum superposition is justified by identifying "axiomatic declarations" for the truth/falsity of $P$ (by virtue of its provability/refutability in T*) with "measurement" in the real world.
This is an expanded version of a contributed paper accepted for publication in the International Journal of Quantum Information as part of the proceedings of the meeting on "Foundations of Quantum Information", FQI04, University of Camerino, April 16-19, 2004 .
philsci-archive.pitt.edu /archive/00001923   (268 words)

  
 Chemical & Engineering News: SCIENCE/TECHNOLOGY - Quantum Computers
A desktop quantum computer is still decades away, but in just a few short years, quantum computing has developed from an ongoing discussion on paper to include a thriving experimental effort that's already produced a few rudimentary quantum computers.
Quantum dots are small, isolated collections of atoms that behave much like a single atom, sharing electrons and a common wavefunction.
A quantum dot on the scale of about 40 nm, and with a single excess electron, could serve as a qubit, with the electron's up and down spin serving as the 0 and 1.
pubs.acs.org /cen/coverstory/7845/7845scit.html   (3622 words)

  
 Alternate View Column AV-45
Quantum superposition is not limited to photons, which are somewhat special because they have no rest mass.
The mathematics of state superposition is special because quantum mechanics describes each state function as a complex variable that has a real part and an "imaginary" part (that behaves like the square root of -1).
They consider a superposition of a number of time-evolving states that differ from one another because of the size of the force that is acting to produce the change with time.
www.npl.washington.edu /AV/altvw45.html   (1946 words)

  
 Learn more about Quantum superposition in the online encyclopedia.   (Site not responding. Last check: 2007-10-21)
Learn more about Quantum superposition in the online encyclopedia.
Quantum superposition occurs when an object simultaneously "possesses" two or more values for an observable quantity (e.g.
Quantum superposition results in many directly observable effects, such as interference peaks from an electron wave in a single-slit experiment.
www.onlineencyclopedia.org /q/qu/quantum_superposition.html   (241 words)

  
 CQC Intros: Quantum Computing   (Site not responding. Last check: 2007-10-21)
During such evolution each number in the superposition is affected and as the result we generate a massive parallel computation albeit in one piece of quantum hardware.
A quantum logic gate, like a classical gate, is a very simple computing device that performs one elementary quantum operation, usually on two qubits, in a given period of time[4].
The quantum theory of computation must in any case be an integral part of the world view of anyone who seeks a fundamental understanding of the quantum theory and the processing of information.
www.qubit.org /oldsite/intros/comp/comp.html   (2952 words)

  
 Quantum Consciousness
L is the scale of the metric quantum gravity fluctuation in the sense of John Archibald Wheeler.
At the moment of collapse, organized quantum exocytosis occurs, i.e., the simultaneous emission of neurotransmitter molecules by the synaptic vesicles, embedded in the "firing zone" of the presynaptic vesicular grids.
Since in the superposition of the quantum states only those participate that are related to the "initial signal", when collapse occurs, it only enhances the probability for "firing" of the relevant neurotransmitter molecules.
www.valdostamuseum.org /hamsmith/QuanCon.html   (9331 words)

  
 BBC - h2g2 - Quantum Superposition
To think of it another way, the neutron is too small to be "seen" because it is smaller that the wavelength of light and light simply passes it without reflecting off it.
Recently quantum physists have been having some sucess with looking at Hardy's paradox, using a technique called "weak measurement", which lets them look at quantum states without disrupting them.
This "weak measurement" using some very strange effects on the quantum level, and while you would think it would collapse the superposition, it doesn't seem to do that.
www.bbc.co.uk /dna/h2g2/A1053776   (786 words)

  
 ASPN : Python Cookbook : Quantum Superposition   (Site not responding. Last check: 2007-10-21)
While this has of course nothing to do with quantum physics, there are some usefull things that can be done with it.
Further, the fewer than 650 lines between the beginning of the module and the beginning of its POD include comments, and the author's style uses a lot more whitespace than necessary, both in blank lines and in putting his {'s on their own lines.
But those are small points compared to the fact that most of the code is devoted to dealing with passing and receiving values in superposition to and from other functions.
aspn.activestate.com /ASPN/Cookbook/Python/Recipe/252125   (859 words)

  
 HP Labs : QIP : People : Bill Munro
His current interests have focussed around the practical implementation for optical and solid state quantum hardware, the generation of optical nonlinearities, the characterisation of quantum states and processes, novel quantum communication and cryptography protocols and quantum metrology.
P.T. Cochrane, G.J. Milburn and W.J. Munro, Macroscopically distinct quantum superposition states as a bosonic code for amplitude damping, Phys.
Bella Schelpe, Adrian Kent, William Munro and Tim Spiller, Inferring superposition and entangelent from measurements in a single basis.
www.hpl.hp.com /research/qip/people/Bill_Munro   (667 words)

  
 Quantum Computer   (Site not responding. Last check: 2007-10-21)
All these quantum effects are exploited in the quantum computer.
You'll learn that, fundamentally, quantum computers are based on two principles in quantum physics, superposition and interference.
The quantum superposition principle allows many calculations to be performed at once, and the interference is the basis of those calculations.
www.cit.gu.edu.au /~s55086/qucomp   (106 words)

  
 References
Quantum cryptography: Uncertainty in the service of privacy.
Quantum theory, the Church-Turing principle and the universal quantum computer.
Quantum computation and complexity theory I. Bulletin of the European Association of Theoretical Computer Sciences, 55:170-207, 1995.
www.cs.cmu.edu /afs/cs/project/jair/pub/volume4/hogg96a-html/node25.html   (405 words)

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