[Paleopsych] SW: On Seeing the World as Quantum-Mechanical

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Physics and Society: On Seeing the World as Quantum-Mechanical

    The following points are made by Richard Conn Henry (Nature 2005
    1) Historically, we have looked to our religious leaders to understand
    the meaning of our lives; the nature of our world. With Galileo
    Galilei (1564-1642), this changed. In establishing that the Earth goes
    around the Sun, Galileo not only succeeded in believing the
    unbelievable himself, but also convinced almost everyone else to do
    the same. This was a stunning accomplishment in "physics outreach"
    and, with the subsequent work of Isaac Newton (1642-1727), physics
    joined religion in seeking to explain our place in the Universe.
    2) The more recent physics revolution of the past 80 years has yet to
    transform general public understanding in a similar way. And yet a
    correct understanding of physics was accessible even to Pythagoras.
    According to Pythagoras, "number is all things", and numbers are
    mental, not mechanical. Likewise, Newton called light "particles",
    knowing the concept to be an "effective theory" --useful, not true. As
    noted by Newton's biographer Richard Westfall: "The ultimate cause of
    atheism, Newton asserted, is 'this notion of bodies having, as it
    were, a complete, absolute and independent reality in themselves.'"
    Newton knew of Newton's rings and was untroubled by what is shallowly
    called "wave/particle duality".
    3) The 1925 discovery of quantum mechanics solved the problem of the
    Universe's nature. Bright physicists were again led to believe the
    unbelievable -- this time, that the Universe is mental. According to
    Sir James Jeans: "the stream of knowledge is heading towards a
    non-mechanical reality; the Universe begins to look more like a great
    thought than like a great machine. Mind no longer appears to be an
    accidental intruder into the realm of matter... we ought rather hail
    it as the creator and governor of the realm of matter." But physicists
    have not yet followed Galileo's example and convinced everyone of the
    wonders of quantum mechanics. As Sir Arthur Eddington explained: "It
    is difficult for the matter-of-fact physicist to accept the view that
    the substratum of everything is of mental character."
    4) In the tenth century, Ibn al-Haytham initiated the view that light
    proceeds from a source, enters the eye, and is perceived. This picture
    is incorrect but is still what most people think occurs, including,
    unless pressed, most physicists. To come to terms with the Universe,
    we must abandon such views. The world is quantum mechanical: we must
    learn to perceive it as such. One benefit of switching humanity to a
    correct perception of the world is the resulting joy of discovering
    the mental nature of the Universe. We have no idea what this mental
    nature implies, but -- the great thing is -- it is true. Beyond the
    acquisition of this perception, physics can no longer help. You may
    descend into solipsism, expand to deism, or something else if you can
    justify it -- just don't ask physics for help.[1-3]
    1. Marburger, J. On the Copenhagen Interpretation of Quantum Mechanics
    http://www.ostp.gov/html/Copenhagentalk.pdf (2002)
    2. Henry, R. C. Am. J. Phys. 58, 1087-1100 (1990)
    3. Steiner, M. The Applicability of Mathematics as a Philosophical
    Problem (Harvard Univ. Press, Cambridge, MA, 1998)
    Nature http://www.nature.com/nature
    Related Material:
    The following points are made by V. Giovannetti et al (Science 2004
    1) Measurement is a physical process, and the accuracy to which
    measurements can be performed is governed by the laws of physics. In
    particular, the behavior of systems at small scales is governed by the
    laws of quantum mechanics, which place limits on the accuracy to which
    measurements can be performed. These limits to accuracy take two
    forms. First, the Heisenberg uncertainty relation [1] imposes an
    intrinsic uncertainty on the values of measurement results of
    complementary observables such as position and momentum, or the
    different components of the angular momentum of a rotating object.
    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.
    2) One important consequence of the physical nature of measurement is
    the so-called "quantum back action": The extraction of information
    from a system can give rise to a feedback effect in which the system
    configuration after the measurement is determined by the measurement
    outcome. For example, the most extreme case (the so-called von Neumann
    or projective measurement) produces a complete determination of the
    post-measurement state. When performing successive measurements,
    quantum back action can be detrimental, because earlier measurements
    can negatively influence successive ones.
    3) A common strategy to get around the negative effect of back action
    and of Heisenberg uncertainty is to design an experimental apparatus
    that monitors only one out of a set of incompatible observables: "less
    is more" [3]. This strategy, called "quantum nondemolition
    measurement" [3-6], is not as simple as it sounds. One has to account
    for the system's interaction with the external environment, which
    tends to extract and disperse information, and for the system
    dynamics, which can combine the measured observable with incompatible
    ones. Another strategy to get around the Heisenberg uncertainty is to
    employ a quantum state in which the uncertainty in the observable to
    be monitored is very small (at the cost of a very large uncertainty in
    the complementary observable). 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.
    4) Most standard measurement techniques do not account for these
    quantum subtleties, so that their precision is limited by otherwise
    avoidable sources of errors. 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").
    These sources of imprecision are not as fundamental as the unavoidable
    Heisenberg uncertainty relations, because they originate only from a
    non-optimal choice of measurement strategy. However, the shot noise
    and standard quantum limits set important benchmarks for the quality
    of a measurement, and they provide an interesting challenge to devise
    quantum strategies that can defeat them.
    5) In summary: Quantum mechanics, through the Heisenberg uncertainty
    principle, imposes limits on the precision of measurement.
    Conventional measurement techniques typically fail to reach these
    limits. Conventional bounds to the precision of measurements such as
    the shot noise limit or the standard quantum limit are not as
    fundamental as the Heisenberg limits and can be overcome using quantum
    strategies that employ "quantum tricks" such as squeezing and
    References (abridged):
    1. H. P. Robertson, Phys. Rev. 34, 163 (1929)
    2. N. Margolus, L. B. Levitin, Physica D 120, 188 (1998)
    3. C. M. Caves, K. S. Thorne, R. W. P. Drever, V. D. Sandberg, M.
    Zimmermann, Rev. Mod. Phys. 52, 341 (1980)
    4. K. Bencheikh, J. A. Levenson, P. Grangier, O. Lopez, Phys. Rev.
    Lett. 75, 3422 (1995)
    5. G. J. Milburn, D. F. Walls, Phys. Rev. A. 28, 2065 (1983)
    Science http://www.sciencemag.org
    Related Material:
    The following points are made by Miles Blencowe (Nature 2003 424:262):
    1) In 1927, Werner Heisenberg (1901-1976) introduced his famous
    quantum principle, which states that the uncertainties in the position
    and the velocity of a particle are inversely proportional to each
    other: a particle's position or its velocity can be known precisely,
    but not both at once. This principle is one of the cornerstones of
    quantum mechanics, and is traditionally relevant to the domain of
    subatomic particles. But what about more familiar macroscopic objects,
    comprising many atoms, that we think of as possessing simultaneously
    well-defined positions and velocities of their center-of-mass? If we
    could be sufficiently precise in our measurements on such objects,
    would we encounter the quantum uncertainty principle at work?
    2) If you clamp one end of a wooden ruler to the edge of a table and
    then pluck the other, free end, it vibrates with decaying amplitude
    and eventually returns to apparent rest. But if you were to look at
    the free end of the ruler under a sufficiently powerful microscope, it
    would not be at rest at all, but jiggling up and down in a random
    fashion. This motion is a consequence of the air molecules striking
    the ruler, as well as of its countless, fluctuating internal defects,
    and is an example of thermal brownian motion.
    3) There are other, quantum fluctuations in the ruler, though, that
    are completely masked by this classical thermal motion. These quantum
    "zero-point" fluctuations have much smaller amplitude and arise from
    the necessary uncertainty in position and velocity stated in
    Heisenberg's principle. The situation is analogous to the hydrogen
    atom, which is stable because the attractive electrostatic force that
    would like to pull the electron into a tighter volume around the
    proton is balanced by the repulsive effect of the electron's
    fluctuating velocity. Similarly, for a macroscopic object such as a
    crystal beam or a ruler, the elastic restoring force on the bent beam
    balances the repulsive effect of its fluctuating center-of-mass
    4) Because the magnitudes of the zero-point fluctuations in position
    and velocity are so small, they can only be detected if the structure
    is cooled down to very low temperatures. As the temperature is
    lowered, the amplitude of thermal motion decreases. Eventually, there
    will be no thermal motion, only pure, temperature-independent
    zero-point fluctuations. At a temperature of about a hundredth of a
    kelvin, zero-point fluctuations should dominate in a structure with a
    mechanical vibration frequency of about one billion cycles per second
    (1 gigahertz, or GHz).
    Nature http://www.nature.com/nature

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