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Cooling levitated nanospheres

Cooling levitated nanospheres. Dr. James Millen Department of Physics and Astronomy University College London Thermodynamics in the quantum regime – Jan 2014. Prof. Peter Barker. The UCL optomechanics group. Cavity cooling nanospheres. Whispering gallery mode cooling.

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Cooling levitated nanospheres

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  1. Cooling levitated nanospheres Dr. James Millen Department of Physics and Astronomy University College London Thermodynamics in the quantum regime – Jan 2014

  2. Prof. Peter Barker The UCL optomechanics group Cavity cooling nanospheres Whispering gallery mode cooling Thermodynamics Spin entanglement in diamond Quantum feedback Prof. Tania Monteiro Dr. James Millen Giacommo Fonseca George Pender Prof. Florian Marquardt Dr.Darrik Chang Dr. James Millen Ying Lia Li Manish Trivedi Dr. Janet Anders Tanapat Deseuwan Dr. James Millen Prof. Sougato Bose Dr. Matteo Scala Dr. Gavin Morley Dr. Anis Raman Dr.AlessioSerafiniDr. James Millen

  3. Optomechanical cooling Thermodynamics Outline Optical mode

  4. Optomechanical cooling

  5. Why? What is the largest “quantum object”? Consider wave nature of matter (Feynman says this contains the“only mystery” in Quantum Mechanics). Gerlichet al. Nature Commun. 2, 263 (2011)

  6. Larger? Technical challenges to standard interferometry: collimated, slow, cold beams. Theoretical issues:(Hornbergeret al.Rev. Mod. Phys. 84 157 (2012) )- Dephasing due to spacetime fluctuations- Gravitational collapse- Spontaneous localization (~108 atoms) What is large?S. Nimmrichter& K. Hornberger Phys. Rev. Lett. 110160403 (2013)

  7. Cooling Just put it in a fridge?

  8. Can entangle light with a macrsocopic degree of freedom. S. Bose, K. Jacobs & P. L. Knight PRA 59 3204 (1999) Cavity Optomechanics Because of the finite cavity ringdown can get dissipation. Marquardt & Girvin Physics 2 40 (2009)

  9. Cavity cooling To produce large quantum objects isolate your mechanical oscillator by levitating. Barker, P. F. and M. N. Shneider Phys. Rev. A, 81(2) (2010) Phys. Rev. A85 021802 (2012) New J. Phys. 15 015001 (2013)

  10. Challenges Parametric noise and laser absorption make reaching low pressures difficult. Spheres of glass are not atoms…

  11. Our system Levitated in an RF trap, cooled optically.

  12. Our system CavityElectrodes

  13. Thermodynamics(with J. Anders and T. Deesuwan)

  14. Our system This system is good for studying thermodynamics (good statistics, easy to observe): Micro heat engineBlickle & BechingerNature Physics8 114 (2012) Landauer’s principleBérutet al.Nature 483 187 (2012) Maxwell’s DemonTobayeet al. Nature Physics (2010) Free energy surfacesGupta at al.Nature (2011)

  15. Our system Optical tweezer (not cavity) in air. Langevin equation:

  16. Dynamics Brownian motion Autocorrelation function 0.1 Position (um) ACF -0.1 20 0 Time (ms) 0 Time lag (ms) 12

  17. Temperature The laser heats the particle. Mean free path much larger than particle.

  18. Two temperature model Two independent baths. Effective CM damping and temperature: See arxiv:1309.3990

  19. Two temperature model Experimental confirmation: (no free-parameter agreement)

  20. Temperature measurement Look at power spectrum (energy, damping, temperature)

  21. Temperature measurement

  22. Why should you be interested? A single large quantum object in a harmonic potential. Immerse in quantum bath? Long interrogation times (good statistics). Fluctuation theories. Can trap ensembles. Heat transfer?

  23. Cavity Optomechanics Can cool a variety of oscillators using the interaction of light with a mechanical degree of freedom.

  24. Cavity Optomechanics

  25. Cavity cooling Barker, P. F. and M. N. Shneider Phys. Rev. A, 81(2) (2010) Force opposes motion Particle moves through cavity field Intracavity intensity Position of undisturbed cavity nodes Lag time in cavity build-up

  26. Cavity cooling Slow cooling due to movement through cavity field. Use two fields. (Chang et al. PNAS 107 1005)

  27. Ground state cooling Strong, broad cooling resonances (less than one phonon at 10-7mbar). Penderet al. Phys. Rev. A85 021802 (2012) Monteiro et al.New J. Phys. 15015001 (2013) Optical mode

  28. Cooling Interferometry Cool sphere (40nm) in a cavity to <n> ~ 0.1 Let particle drop, Gaussian state evolves. Pulsed measurement in second cavity produces superposition state. Separated by diameter of sphere! Further free-fall produces interference pattern in c.o.m. position. Romero-Isartet al.Phys. Rev. Lett. 107 020405 (2011)

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