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    New study suggests researchers can now test the 'theory of everything


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    New study suggests researchers can now test the 'theory of everything Empty New study suggests researchers can now test the 'theory of everything

    Post  Studeo on Tue Sep 07, 2010 7:55 pm

    New study suggests researchers can now test the 'theory of everything'
    September 1, 2010

    Researchers discover how to conduct first test of 'untestable' string theory

    ( -- Researchers describe how to carry out the first
    experimental test of string theory in a paper published tomorrow in
    Physical Review Letters.

    String theory was originally developed to describe the fundamental
    particles and forces that make up our universe. The new research, led
    by a team from Imperial College London, describes the unexpected
    discovery that string theory also seems to predict the behaviour of
    entangled quantum particles. As this prediction can be tested in the
    laboratory, researchers can now test string theory.

    Over the last 25 years, string theory has become physicists' favourite
    contender for the 'theory of everything', reconciling what we know
    about the incredibly small from particle physics with our
    understanding of the very large from our studies of cosmology. Using
    the theory to predict how entangled quantum particles behave provides
    the first opportunity to test string theory by experiment.

    "If experiments prove that our predictions about quantum entanglement
    are correct, this will demonstrate that string theory 'works' to
    predict the behaviour of entangled quantum systems," said Professor
    Mike Duff FRS, lead author of the study from the Department of
    Theoretical Physics at Imperial College London.

    "This will not be proof that string theory is the right 'theory of
    everything' that is being sought by cosmologists and particle
    physicists. However, it will be very important to theoreticians
    because it will demonstrate whether or not string theory works, even
    if its application is in an unexpected and unrelated area of physics,"
    added Professor Duff.

    Professor Duff recalled sitting in a conference in Tasmania where a
    colleague was presenting the mathematical formulae that describe
    quantum entanglement: "I suddenly recognised his formulae as similar
    to some I had developed a few years earlier while using string theory
    to describe black holes. When I returned to the UK I checked my
    notebooks and confirmed that the maths from these very different areas
    was indeed identical."

    The discovery that string theory seems to make predictions about
    quantum entanglement is completely unexpected, but because quantum
    entanglement can be measured in the lab, it does mean that at last
    researchers can test predictions based on string theory. There is no
    obvious connection to explain why a theory that is being developed to
    describe the fundamental workings of our universe is useful for
    predicting the behaviour of entangled quantum systems. "This may be
    telling us something very deep about the world we live in, or it may
    be no more than a quirky coincidence", concluded Professor Duff.
    "Either way, it's useful."

    String theory

    String theory, and its extension M-theory, are mathematical
    descriptions of the universe. They have been developed, over the last
    25 years, by theoreticians seeking to reconcile the theories of
    general relativity and quantum mechanics. (The former describes the
    universe at the level of cosmology - the very large, while the latter
    describes the universe at the level of particle physics - the
    incredibly small). One of the major bugbears, especially of M-theory,
    is that it describes billions of different universes and ‘anything’
    can be accommodated in one or other of the M-theory universes.
    Researchers have no way of testing which of the answers that
    string/M-theory gives us is ‘right’. Indeed, they all may be right and
    we live in one universe among an infinite number of universes. So far
    no one has been able to make a prediction, using string theory, that
    can be tested to see if it is correct or not.

    Qubit (quantum bit) entanglement

    Under very precisely controlled conditions it is possible to entangle
    the properties of two quantum particles (two quantum bits, or qubits),
    for example two photons. If you then measure the state of one of these
    entangled particles, you immediately affect the state of its partner.
    And this is true if the particles are close to one another or
    separated by enormous distance. Hence Einstein’s apposite description
    of quantum entanglement as ‘spooky action at a distance’. It is
    possible to entangle more than two qubits, but calculating how the
    particles are entangled with one another becomes increasingly complex
    as more particles are included.

    Professor Duff and his colleagues realised that the mathematical
    description of the pattern of entanglement between three qubits
    resembles the mathematical description, in string theory, of a
    particular class of black holes. Thus, by combining their knowledge of
    two of the strangest phenomena in the universe, black holes and
    quantum entanglement, they realised they could use string theory to
    produce a prediction that could be tested. Using the string theory
    mathematics that describes black holes, they predicted the pattern of
    entanglement that will occur when four qubits are entangled with one
    another. (The answer to this problem has not been calculated before.)
    Although it is technically difficult to do, the pattern of
    entanglement between four entangled qubits could be measured in the
    laboratory and the accuracy of this prediction tested.

    More information: M. J. Duff FRS et al., “Four-qubit entanglement from
    string theory.” Physical Review Letters 2010.

    Provided by Imperial College London

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