Entanglement of massive bodies

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Entanglement of massive bodies
School of Physics and Astronomy FACULTY OF
MATHEMATICAL AND PHYSICAL SCIENCES

• Vlatko Vedral
• University of Leeds, UK
• National University of Singapore

v.vedral_at_leeds.ac.uk
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In collaboration with

• Jacob Dunningham, Marcelo Terra Cunha and Libby
  Heaney (Leeds)
• Also,
• Janet Anders, Dago Kaszlikowski (Singapore) and
  Jenny Hide and Wonmin Son (Leeds).

See Many-body entanglement, Amico, Fazio,
Osterloh and Vedral, to appear in Rev. Mod. Phys.
(2007).
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Motivation

• Fundamental Classical/Quantum transition,
  Non-locality, Failure of QM
• Many body physics information processing, new
  PTs, simulations

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Atomic Beam Quantum Computer
P. Blythe and B.Varcoe New Journal of Physics,
8, 231 (2006)
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An Atomic Beam Quantum ComputerMiniature
Microwave Resonators
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Main message
Entanglement should be seen as between modes, not
just particles. Corollary We do not need two
particles to have entanglement. One will
suffice.
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Particles not special

• ?The term particle survives in modern physics
  but very little of its classical meaning remains.
  A particle can now best be defined as the
  conceptual carrier of a set of variates. . . It
  is also conceived as the occupant of a state
  defined by the same set of variates... It might
  seem desirable to distinguish the mathematical
  fictions from actual particles but it is
  difficult to find any logical basis for such a
  distinction. Discovering a particle means
  observing certain effects which are accepted as
  proof of its existence.??
• A. S. Eddington, Fundamental Theory, (Cambridge
  University Press., Cambridge, 1942)?pp. 30-31.

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Bosons at T0
Infinite range entanglement!
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Bosons at T0
Infinite range entanglement!
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Bosons at T0
Infinite range entanglement!
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Bosons at T0
Infinite range entanglement!
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Bosons at T0
Infinite range entanglement!
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Bosons at T0
Infinite range entanglement!
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Superposition Entanglement
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Single particle atom entanglement
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My Favourite Viva Question
How can we ever have a superposition?
True for Stern Gerlach, beam-splitters,
lasersanything.
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But we dont know the phase!?
Who cares?
This is why preparation and read out are done
with the same laser (phase matching kind of
thing).
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Single particle atom entanglement
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Only One Mystery
Feynman There is only one mystery in quantum
mechanics Therefore Superposition
Entanglement ( Non-locality?)
Key observation Single particle superposition in
first quantisation
becomes mode entanglement in second.
(See Terra Cunha, Dunningham Vedral, to appear
Proc. Roy Soc. M. R. Dowling, S. D. Bartlett,
T. Rudolph and R. W. Spekkens, Phys. Rev. A
(2006)) Ashhab, Maruyama, Nori, Phys. Rev. A 75,
022108 (2007)
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Conclusions

• Single particle superposition, entanglement and
  nonlocality the same.
• This is good news, since in quantum field theory
  particles are not
• fundamental. Particle is just an excitation of a
  mode of some field,
• therefore particles identical and there should be
  no fundamental
• difference between one, two and more particles.
• All entanglement mode entanglement.
• Interesting question for mixed states is
  entanglement the same as
• nonlocality? What about mixedness and
  entanglement?

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Thanks to