New study suggests researchers can now test the 'theory of everything'
http://www.physorg.com/news202553083.html
September 1, 2010
Researchers discover how to conduct first test of 'untestable' string theory
(PhysOrg.com) -- 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. http://prl.aps.org …
/i10/e100507
Provided by Imperial College London
http://www.physorg.com/news202553083.html
September 1, 2010
Researchers discover how to conduct first test of 'untestable' string theory
(PhysOrg.com) -- 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. http://prl.aps.org …
/i10/e100507
Provided by Imperial College London
