Les Puces à Atomes. Jakob Reichel. Laboratoire Kastler Brossel de l E.N.S., Paris

Transcription

1 Les Puces à Atomes Jakob Reichel Laboratoire Kastler Brossel de l E.N.S., Paris

2 Atom chips: Cold atoms meet the nanoworld ~ 100 nm BEC (~ 10 5 atoms, ~ 100 nk) microstructured surface bulk material ( ~ 300 K)

3 What is a Bose-Einstein Condensate (BEC)? Thousands of atoms sharing the same quantum state A macroscopic matter wave λ db = 2 h 2π mkt If this is such an elementary state of matter, why did it take so long to produce it? Because temperature must be extremely low! 3 nλ db ~ 1

4 More concretely glass cell containing the atoms magnetic coils (100s of Amps) LKB (Jean Dalibard) laser optics

5 Laser Cooling false color image of Cs MOT microkelvin temperature cm/s speed at/cm 3 density 1997 Nobel prize

6 The route to BEC 3 nλ db 1 BEC achieved in Nobel prize 300 K 10 µk 500 nk

7 MPQ München BEC and Atom Lasers

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9 Magnetic microtrap idea: Replace macroscopic coils by microscopic wires B = µ 0 I 2π r 2 r = 10 µm : 15 T/cm I = 1 A r = 1 mm : 15 G/cm wire current I (~ 1A) + external bias field B 0 (~ G) trapping freq. ~ 100 khz

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11 On-chip BEC: Simple & fast Single, small cell (no differential pumping, no 2 nd set of lasers) Base pressure: mbar (10-11 mbar is standard) < 10 s cycle time ( 1 min is standard) 22.4 mm W. Hänsel, P. Hommelhoff, T. W. Hänsch and J. Reichel, Nature 413, (2001). Also see C. Zimmermann group, PRL 87, (2001).

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13 it has become much easier

14 Beyond trapping: Atomic conveyor et al.

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16 Atomic Conveyor: Theme and Variations conveyor belt (sinusoidal modulation) optimized conveyor belt (faster transport with less heating) linear collider integrated cold atom source...with switchable output adiabatic splitting and merging see also: splitting and merging in waveguides Anderson / Cornell groups (Boulder) Schmiedmayer group (Heidelberg)

17 Atom Chips - What for? Metrology Small, integrated system for frequency standards and atom interferometry Atom-surface physics Scanning BEC microscopy Quantum Information Scalable quantum system with good coherence properties BEC-nanodevice interaction SQUIDS, SETs, can be integrated on atom chip

18 Metrology I: Integrated atom optics Motivation: atom interferometer on a chip analogy with fiber optics compact, high sensitivity sensors T. Schumm et al., arxiv:quant-ph/ (2005)

19 Metrology II: Atomic Clock on a Chip Coherence measurements: Ramsey spectroscopy BNM-SYRTE + LKB collaboration: Expect stability in 1s. Outperform best existing portable clocks. coherence lifetime (d = 9 µm): τ coh = 2.8 s ~ 10 4 τ gate similar to experiments in macroscopic magnetic traps (Cornell group, Boulder) Ph. Treutlein et al., PRL 92, (2004)

20 Atom-Surface Physics: Measuring Magnetic Fields with Trapped Atoms Scanning BEC Microscopy Corrugations : Elongated atom cloud trapped over current-carrying wire may break up into lumps at very low temperature A problem for guided-atom interferometers (not so much for traps and QIP) J. Fortagh et al. (C. Zimmermann group), PRA 66, R (2002) electroplated wire 2004: Corrugated edges of (electroplated) wires identified as main reason. Can be improved with better fabrication techniques! (direct e-beam writing, evaporation instead of electroplating) Aspect / Bouchoule / Westbrook group, physics/ , physics/ The same method can be sold as a magnetic microscopy method: Wildermuth et al. Nature (2005) Sensitivity / Resolution: ~ 10-9 T / ~ 3 µm

21 Quantum Information: A Scalable neutral-atom system? Isolated system, long coherence time Coherence lifetimes τ coh ~ seconds, τ coh ~ τ gate required for error correction Highly developed manipulation techniques on micro / nanocircuits? Miniaturization, parallelization Scalable manipulation techniques from J. Schmiedmayer et al., J.Mod.Opt. 49, 1375 (2002)

22 Baby BEC ceramic substrate (AlN) epoxy dielectric mirror gold µm S. Du, M. B. Squires, Y. Imai, L. Czaia, R.A. Saravanan, V. Bright, J. Reichel, T. W. Hänsch, and D. Z. Anderson, Phys. Rev. A 70, (2004).

23 Towards a portable BEC Bremen drop tower: 4.7 s of microgravity Portable BEC apparatus will be installed in capsule. Experiment is powered by MPQ atom chip. Consortium: ZARM Bremen, U Hannover, U Hamburg, HU Berlin, U Ulm, MPQ/ENS Assembly scheduled for late 2005

24 BEC-Nanodevice Coupling: Detecting Single Phonons of NEMS Resonator Motion Fabricate small ferromagnetic (Co) island on resonator B(t) trap B-field/ atomic spin Resonator oscillations Co z(t) oscillating B-field couples to atomic spin Magnetic field spectrum S B (ω) is proportional to resonator spectrum S z (ω) S B (ω)» S z (ω) ω L ω 0 ω Resonator motion induces spin flips: P. Treutlein & J. Reichel, to be published

25 BEC-Nanodevice Coupling: There are many possibilities Example: Coupling of Rydberg atoms via on-chip superconducting resonator Proposal by A.S. Sorensen et al., PRL 92, (2004) Entangle 2 quantum systems of very different size Decoherence? however, most of them require a low-temperature sample cryostat (complicated experiments) Experiment under way at ENS Paris: P. Hyafil et al., PRL 93, (2004)

26 What is spooky and what is normal depends on our everyday experience Portable quantum devices may bring quantum phenomena into the everyday world