Cavity cooling of a single atom James Millen 21/01/09 Outline Cavity cooling of

Cavity cooling of a single atom James Millen 21/01/09 Outline Cavity cooling of www.phwiki.com

Cavity cooling of a single atom James Millen 21/01/09 Outline Cavity cooling of

Beckwith, Alisa, Jazz Director;Evening Jazz Host has reference to this Academic Journal, PHwiki organized this Journal Cavity cooling of a single atom James Millen 21/01/09 Outline Cavity cooling of a single atom – Journal club talk 21-01-09 Introduction to Cavity Quantum Electrodynamics (QED) – The Jaynes-Cummings model – Examples of the behaviour of an atom in a cavity Cavity cooling of a single atom [1] 2 Why cavity QED Cavity cooling of a single atom – Journal club talk 21-01-09 Why study the behaviour of an atom in a cavity It is a very simple system in which to study the interaction of light in addition to matter It is a rich testing ground as long as elementary QM issues, e.g. EPR paradox, Schrödinger’s cat Decoherence rates can be made very small Novel experiments: single atom laser (Kimble), trapping a single atom with a single photon (Rempe) 3

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Jaynes-Cummings model (1) [2] Cavity cooling of a single atom – Journal club talk 21-01-09 Consider an atom interacting with an electromagnetic field in free space 4 Jaynes-Cummings model (2) [2] Cavity cooling of a single atom – Journal club talk 21-01-09 Consider a pair of mirrors as long as ming a cavity of a set separation 5 Dynamical Stark effect (1) Cavity cooling of a single atom – Journal club talk 21-01-09 This Hamiltonian has an analytic solution N.B. This is as long as light on resonance with the atomic transition 6

Dynamical Stark effect (2) Cavity cooling of a single atom – Journal club talk 21-01-09 This yields eigenfrequencies: Splitting non-zero in presence of coupling g, even if n = 0! (Vacuum splitting observed, i.e. Haroche [3]) 7 A neat example Cavity cooling of a single atom – Journal club talk 21-01-09 8 Cavity cooling of a single atom – Journal club talk 21-01-09 Cavity Cooling of a Single Atom P. Maunz, T. Puppe, I. Scuster, N. Syassen, P.W.H. Pinkse & G. Rempe Max-Planck-Institut für Quantenoptik Nature 428 (2004) [1] 9

Motivation Cavity cooling of a single atom – Journal club talk 21-01-09 Conventional laser cooling schemes rely on repeated cycles of optical pumping in addition to spontaneous emission Spontaneous emission provides dissipation, removing entropy In the scheme presented here dissipation is provided by photons leaving the cavity. This is cooling without excitation This allows cooling of systems such as molecules or BECs [4], or the non-destructive cooling of qubits [5] 10 Principle Cavity cooling of a single atom – Journal club talk 21-01-09 Light blue shifted from resonance At node the atom does not interact with the field If the atom moves towards an anti-node it does interact The frequency of the light is blue-shifted, it has gained energy The intensity rapidly drops in the cavity, the atom has lost EK 11 A problem Cavity cooling of a single atom – Journal club talk 21-01-09 Can an atom gain energy by moving from an anti-node to a node No, because as long as an atom initially at an anti-node the intra-cavity intensity is very low Excitations are heavily suppressed: – at the node there are no interactions – at the anti-node the cavity field is very low Lowest temperature not limited by linewidth dd(Doppler limit) 12

The experiment Cavity cooling of a single atom – Journal club talk 21-01-09 780.2nm C = 0 a/2 = 35MHz Finesse = FSR / B in addition to width F = 4.4×105 Decay /2 = 1.4MHz 85Rb( <10cms-1) Single photon counter used, QE 32% Single atom causes a factor of 100 reduction in transmission 785.3nm L = 120m 13 Trapping Cavity cooling of a single atom – Journal club talk 21-01-09 Nodes in addition to antinodes of dipole trap in addition to probe coincide at centre Atoms trapped away from centre are neither cooled nor detected by the probe Initially the trap is 400K deep, when atom detected it’s deepened to 1.5mK. 95% of detected atoms are trapped 14 The experiments Cavity cooling of a single atom – Journal club talk 21-01-09 Trap lifetime: The lifetime of the dipole trap is measured in addition to found to depend upon the frequency stability of the laser Trap lifetime with cooling: The introduction of very low intensity cooling light increases the trap lifetime Direct cooling: The cooling rate is calculated as long as an atom allowed to cool as long as a period of time Cooling in a trap: An atom in a trap is periodically cooled, in addition to an increase in trap lifetime is observed 15 Trap lifetime (1) Cavity cooling of a single atom – Journal club talk 21-01-09 Dipole trap in addition to probe on, atom detected Probe turned off as long as t Probe turned back on, presence of atom checked 16 Trap lifetime (2) Cavity cooling of a single atom – Journal club talk 21-01-09 Lifetime found to be 18ms Light scattering arguments give a limit of 85s, cavity QED a limit of 200ms [6] Low lifetime due to heating through frequency fluctuations Note: Heating proportional to trap frequency axial trap frequency 100 radial trap frequency most atoms escape antinode in addition to hit a mirror 17 Trap lifetime with cooling (1) Cavity cooling of a single atom – Journal club talk 21-01-09 Dipole trap in addition to probe on, atom detected Probe reduced in power as long as t Probe turned back on, presence of atom checked 18 Trap lifetime with cooling (2) Cavity cooling of a single atom – Journal club talk 21-01-09 Pre-frequency stabilization improvement Post-frequency stabilization improvement A probe power of only 0.11pW doubles the storage time (0.11pW corresponds to only 0.0015 photons in the cavity!) At higher probe powers the storage time is decreased The probe power must be high enough to compensate as long as axial heating from the dipole trap, in addition to low enough to prevent radial loss Monte Carlo simulations confirm that at low probe powers axial loss dominates, at high probe powers radial loss dominates 19 Direct cooling (1) Cavity cooling of a single atom – Journal club talk 21-01-09 C/2 = 9MHz as long as 100s Theory predicts heating [6] C = 0 as long as 500s Atoms are cooled (PP = 2.25pW) 20 Direct cooling (2) Cavity cooling of a single atom – Journal club talk 21-01-09 For the first ~100s the atom is cooled After this the atom is localised at an antinode From the time taken as long as this localisation to happen, a friction coefficient can be extracted, in addition to hence a cooling rate For the same levels of excitation in free space this is 5x faster than Sisyphus cooling, in addition to 14x faster than Doppler cooling 21 Cooling in a dipole trap (1) Cavity cooling of a single atom – Journal club talk 21-01-09 If artificially introducing heating isn’t to your taste Dipole trap continuously on Probe pulsed on as long as 100s every 2ms. Probe cools in addition to detects (1.5pW) 22 Cooling in a dipole trap (2) Cavity cooling of a single atom – Journal club talk 21-01-09 The lifetime of the atoms in the dipole trap without cooling is 31ms With the short cooling bursts the lifetime is increased to 47ms 100s corresponds to a duty cycle of only 5%, yet the storage time is increased by ~50% It takes longer to heat the atom out of the trap in the presence of the probe, hence the probe is decreasing the kinetic energy (cooling) 23 Summary Cavity cooling of a single atom – Journal club talk 21-01-09 An atom can be cooled in a cavity by exploiting the excitation of the cavity part of a coupled atom-cavity system Storage times as long as an atom in an intra-cavity dipole trap can be doubled by application of an exceedingly weak almost resonant probe beam Cooling rates are considerably faster than more conventional laser cooling methods, relying on repeated cycles of excitation in addition to spontaneous emission 24 Beckwith, Alisa WUAL-FM Jazz Director;Evening Jazz Host www.phwiki.com

References Cavity cooling of a single atom – Journal club talk 21-01-09 [1] P. Maunz, T. Puppe, I. Schuster, N. Syassen, P. W. H. Pinkse in addition to G. Rempe “Cavity cooling of a single atom” Nature 428, 50-52 (4 March 2004) [2] E.T. Jaynes in addition to F. W. Cummings “Comparison of quantum in addition to semiclassical radiation theories with application to the beam maser” Proc. IEEE 51, 89 (1963) [3] F. Bernardot, P. Nussenzveig, M. Brune, J. M. Raimond in addition to S. Haroche “Vacuum Rabi Splitting Observed on a Microscopic Atomic Sample in a Microwave Cavity” Europhys. Lett. 17 33-38 (1992) [4] P. Horak in addition to H. Ritsch “Dissipative dynamics of Bose condensates in optical cavities” Phys. Rev. A 63, 023603 (2001) [5] A. Griessner, D. Jaksch in addition to P. Zoller “Cavity assisted nondestructive laser cooling of atomic qubits” arXiv quant-ph/0311054 [6] P. Horak, G. Hechenblaikner, K.M. Gheri, H. Stecher in addition to H. Ritsch “Cavity-induced atom cooling in the strong coupling regime” Phys. Rev. Lett. 79 (1997) 25

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