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Title “When freezing cold is not cold enough - new forms of matter close to absolute zero temperature” Wolfgang Ketterle Massachusetts Institute of Technology MIT-Harvard Center for Ultracold Atoms 9/2/09 Meridian Lecture Space Telescope Science Institute Baltimore

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What is energy Quantum Gases The coldest matter in the universe

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What is temperature What is temperature? A measure of energy One form of energy is motion (kinetic energy).

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Cold particles move slowly Hot particles are fast

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What is the lowest temperatures possible?

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What is temperature Zero degree Kelvin (-273 degrees Celsius, -460 degrees Fahrenheit) is the zero point for energy

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The highest temperature is infinite (In principle it is possible for particles to have arbitrarily high kinetic energies – until they become so heavy (due to E=mc 2 ) that they from a black hole – at the Planck temperature of 10 32 K)

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What is temperature What is the difference in temperature between summer and winter? 20 %

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How cold is interstellar space? 3 K

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Nanokelvin temperatures How cold is it in our laboratories? Nanokelvin: A billion times colder than interstellar space

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Nanokelvin temperatures Why can you make new discoveries at cold temperatures?

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Nobel medal

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Atom slow down What happens to atoms at low temperatures? They slow down 600 mph (300 m/sec)1 cm/sec They march in lockstep

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Molecule of the year Matter made of waves!

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Molecule of the year

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Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? T=T c Bose-Einstein distribution

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Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? Bose-Einstein distribution T

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Why do photons not Bose condense Energy Population per energy state What is Bose Einstein Condensation? Bose-Einstein distribution T

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Laser beam and light bulb Laser lightOrdinary light Photons/atoms moving randomly Photons/atoms are one big wave

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Bose/Einstein * 1925

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BE statistics and black body law Max Planck Black-Body Radiation “Photons” Gases (Atoms and Molecules)

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The concepts The cooling methods Laser cooling Evaporative cooling

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Hot atoms

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Laser beams

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Hot atoms Laser beams Fluorescence

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Laser beams Fluorescence If the emitted radiation is blue shifted (e.g. by the Doppler effect) ….

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Cold atoms: 10 – 100 K Laser beams Fluorescence Chu, Cohen-Tannoudji, Phillips, Pritchard, Ashkin, Lethokov, Hänsch, Schawlow, Wineland …

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MOT 2.5 cm Laser cooling

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The concepts Evaporative cooling

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Magnetic trap setup (GIF) Phillips et al. (1985) Pritchard et al. (1987)

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Guinness Book Record

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The real challenge One challenge … experimental complexity

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WK and Dark SPOT Sodium laser cooling experiment (1992)

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Sodium BEC I experiment (2001)

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Evaporative cooling Dan KleppnerTom Greytak Dave Pritchard

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Family tree Dan Kleppner Dave Pritchard Eric CornellCarl WiemanWolfgang Ketterle Bill Phillips PhD Postdoc Under- graduate PhD Randy Hulet PhD Norman Ramsey PhD I.I. Rabi PhD Postdoc

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Key factors for success: Funding Technical infrastructure Excellent collaborators Tradition and mentors

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Probing BEC How do we show that the Bose-Einstein condensate has very low energy?

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Magnetic trap setup The condensate a puff of gas 100,000 thinner than air size comparable to the thickness of a hair magnetically suspended in an ultrahigh vacuum chamber

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Effusive beam How to measure temperature? Kinetic energy mv 2 /2 = k B T/2

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Effusive beam How to measure temperature? Kinetic energy mv 2 /2 = k B T/2

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CCD

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Ballistic expansion:direct information about velocity distribution

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CCD Absorption image: shadow of atoms Ballistic expansion:direct information about velocity distribution

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BEC B&W AVI The shadow of a cloud of bosons as the temperature is decreased (Ballistic expansion for a fixed time-of-flight) Temperature is linearly related to the rf frequency which controls the evaporation

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Hour distribution Distribution of the times when data images were taken during one year between 2/98-1/99

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Key factors for success: Some funding Technical infrastructure Excellent collaborators Tradition and mentors

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Key factors for success: Some funding Technical infrastructure Excellent collaborators Tradition and mentors Physical endurance

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Molecule of the year How can you prove that atoms march in lockstep? Atoms are one single wave Atoms are coherent

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One paint ball on a white wall Two Paint does not show wave properties

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One laser beam on a white wall Light shows wave properties

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One laser beam on a white wall Two Fringe pattern: Bright-dark-bright-dark Light shows wave properties

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Water waves

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Two condensates... Cutting condensates

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Interference of two Bose-Einstein condensates Interference pattern Andrews, Townsend, Miesner, Durfee, Kurn, Ketterle, Science 275, 589 (1997)

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Nobel Diploma

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How do we show that the gas is superfluid?

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Rotating buckets

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Velocity profile Rigid body:

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Vortex structure

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Vortices in Nature Vortices in nature

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Toilet 1

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Toilet

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Spinning a Bose-Einstein condensate Rotating green laser beams The rotating bucket experiment with a superfluid gas 100,000 thinner than air Two-component vortex Boulder, 1999 Single-component vortices Paris, 1999 Boulder, 2000 MIT 2001 Oxford 2001 J. Abo-Shaeer, C. Raman, J.M. Vogels, W.Ketterle, Science, 4/20/2001

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BEC on a microchip Current Research

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Loading sodium BECs into atom chips with optical tweezers BEC production BEC arrival 44 cm T.L.Gustavson, A.P.Chikkatur, A.E.Leanhardt, A.Görlitz, S.Gupta, D.E.Pritchard, W. Ketterle, Phys. Rev. Lett. 88, 020401 (2002). Atom chip with waveguides

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Splitting of condensates 15ms Expansion Two condensates 1mm One trapped condensate

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Trapped 15ms expansion 1mm Two condensates Splitting of condensates

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Two condensates Splitting of condensates Y. Shin, C. Sanner, G.-B. Jo, T. A. Pasquini, M. Saba, W. Ketterle, D. E. Pritchard, M. Vengalattore, and M. Prentiss: Phys. Rev. A 72, 021604(R) (2005).

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Two condensates Splitting of condensates The goal: Atom interferometry: Matter wave sensors Use ultracold atoms to sense Rotation Navigation Gravitation Geological exploration

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Cold molecules Cold fermions Current Research

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Can electrons form a Bose-Einstein condensate and become superfluid (superconducting)? Two kinds of particles Bosons: Particles with an even number of protons, neutrons and electrons Fermions: odd number of constituents Only bosons can Bose-Einstein condense!

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Can electrons form a Bose-Einstein condensate and become superfluid (superconducting)? Two kinds of particles Bosons: Particles with an even number of protons, neutrons and electrons Fermions: odd number of constituents Only bosons can Bose-Einstein condense! How can electrons (fermions) condense? They have to form pairs!

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Can we learn something about superconductivity of electrons from cold atoms? Yes, by studying pairing and superfluidity of atoms with an odd number of protons, electrons and neutrons

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M.W. Zwierlein, C. A. Stan, C. H. Schunck, S.M. F. Raupach, S. Gupta, Z. Hadzibabic, W.K., Phys. Rev. Lett. 91, 250401 (2003) BEC of Fermion Pairs (“Molecules”) Boulder Nov ‘03 Innsbruck Nov ‘03, Jan ’04 MIT Nov ’03 Paris March ’04 Rice, Duke These days: Up to 10 million condensed molecules

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Atomic Bose-Einstein condensate (sodium) Molecular Bose-Einstein condensate (lithium 6 Li 2 ) Pairs of fermionic atoms (lithium-6) Gallery of superfluid gases

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Ultracold atoms A “toolbox” for designer matter Normal matter Tightly packed atoms Complicated Interactions Impurities and defects

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Matter of ultracold atoms 100 million times lower density Interactions understood and controlled no impurities exact calculations possible Ultracold atoms A “toolbox” for designer matter Need 100 million times colder temperatures

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