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HYPER

HYPER. Hyper-Precision Cold Atom Interferometry in Space Limits on Quantum Gravity. ROBERT BINGHAM. Rutherford Appleton Laboratory,Chilton, Didcot, Oxon. OX11 0QX. HYPER - Atom interferometers and Quantum Gravity.

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HYPER

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  1. HYPER Hyper-Precision Cold Atom Interferometry in Space Limits on Quantum Gravity ROBERT BINGHAM Rutherford Appleton Laboratory,Chilton, Didcot, Oxon. OX11 0QX

  2. HYPER - Atom interferometers and Quantum Gravity • Grand unification theory (GUT) predict that the four forces of nature unify close to the planck scale. • Spacetime is smooth on the normal scales but granulated due to quantum gravity on the Planck scale  Quantum Foam • Planck time planck  G c   s • Planck length cplanck  G c2   35 m • Planck mass Mplanck  c/G  10-8kg • Planck energy  1019 GeV Planck mass

  3. HYPER - Atom interferometers and Quantum Gravity • Quantum Foam • Spacetime at the Planck scale is topologically nontrivial, manifesting a granulated structure  Quantum Foam • Quantum decoherence puts limits on spacetime fluctuations at the Planck scale. • Semi-classical and Superstring theory support the idea of loss of quantum coherence.

  4. HYPER - Atom Interferometers and Quantum Gravity • How can an atom interferometer measure physics on the Planck scale? • Einstein’s (1905) Brownian motion work of inferred properties of atoms by • observing stochastic motion of macrostructure’s • Space time fluctuations on the Planck scale produce stochastic phase shifts. •  • Possible to measure space-time • fluctuation Amplitude Aplanck Aplanck Diffusion of the wave function. Produces decoherence in an atom interferometer (Powers & Percival 1999, Ellis 1990))

  5. HYPER - Atom Interferometers and Quantum Gravity • Stochastic Process • Quantum gravity fluctuations  stochastic phase shifts • A stochastic process like Brownian • motion is a diffusion process  • Regular phase due to smooth spacetime • shift is . • Space time fluctuations  regular • phase  multiplied by to/. • Results in fluctuating phase • to • [Percival 1997]

  6. HYPER - Atom Interferometers and Quantum Gravity • Physics of Decoherence • Difficult to avoid interaction with environment. • Natural Vibrations of the system. • Collisions with ambient particles. • Interaction with its own components. • Black body radiation. • Spacetime time quantum fluctuations.

  7. Atom Interferometer Classical gravitational fields  regular phase change  Along a path with an interval of proper time,   =  Mc2/ quantum angular frequency, mass M of the atom. (Atom mass number   1. s) • Spacetime fluctuations •  Stochastic phase change () •   to/   ( planck 

  8. HYPER - Atom Interferometers and Quantum Gravity • Granulation of space-time - Universe no longer four dimensional, • higher number of dimensions are required. • e.g. Superstring theory - 10 dimensions • Length scale below which granulation is important • This is an effective cut-off for Quantum gravity theories determined by the amplitude of zero point gravitational fluctuations • where is the cut-off frequency, and • From theoretical considerations  is in range 102 - 106 • Current experiments using atom Interferometers by Peters et al., 1997 set a lower bound of  > 18. • Improvements on experimental sensitivity can raise this value.

  9. Quantum Limits on Atom Interferometers • In matter interferometers it is difficult to avoid interactions with the environment and these also suppress the interference. • The decoherence may be caused by interaction with blackbody radiation, collisions, restraint by a tie down system or even interaction with its own components/atoms. • Position uncertainty limit is • The challenge is to detect the spacetime fluctuations unambiguously. • HYPER will put upper limits to the measurement of decoherence providing tests for the various theories.

  10. HYPER - Atom Interferometers and Quantum Gravity • Conclusions • Theories of Quantum gravity support the idea of loss of coherence in matter interferometers. • In matter interferometers it is difficult to avoid interactionswith the environment. • The challenge is to detect the spacetime fluctuations unambiguously • HYPERwill put upper limits to the measurement of decoherence providing tests for the various theories of quantum gravity.

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