Manipulating and observing individual atoms

The team: Alicia V. Carpentier, Tzahi Grünzweig, Andrew Hilliard, Yin Fung, and Matt McGovern

Collaborator:Professor Thad G Walker University of Wisconsin

Outline

• Historical Background

• Motivation

• Experimental Apparatus

• Imaging and counting of individual atoms in a microscopic volume

• Isolating individual atoms

• Conclusions

History of Atoms

• Introduced by early Indian and Greek philosophers• Picked up by chemists in 17’th and 18’th centuries• Rutherford/Bohr:

• Scanning Tunneling Microscopy

• Individual Ions

“The present state of atomic theory is characterized by the fact that we not only believe the existence of atoms to be proved beyond a doubt, but also we even believe that we have an intimate knowledge of the constituents of the individual atoms.”

Motivation

• Direct investigations of the quantum world: the dream of scientists for the past century

• Quantum information processing → Ultra fast computers of the future

• Atomic scale engineering: the ultimate limit of small scale engineering

What is the problem with neutral atoms?

• They are very small

They are hard to “see”

They move around at high speeds

• They are electrically neutral

They are hard to hold on to

They are difficult to separate

How to stop atoms

Radiation Pressure

LASER Cooling

Optical Tweezers

Optical Dipole Force

Our experiments

In Reality

Problems with counting atoms using flourecense imaging

• Many photons need to be scattered

• Radiation pressure blows atoms away

• Light assisted collisions cause rapid loss at high densities

Light assisted collisions (photo-chemistry)

Cooling with blue detuned light

Image of single atom

Counting Atoms

None 1 Atom 2 Atoms

M. McGovern, Andrew Hilliard, T. Grünzweig, and M. F. A., Opt. Lett., 36, 1041, 2011.

Preparing individual atoms

At each site, atoms undergo pairwise light-assisted collisions, which can either significantly increase their kinetic energy, or cause them to form a molecule. Either way, both atoms are lost more quickly than we can observe, so that sites that are initially occupied by an even number of atoms become empty and sites that are initially odd-occupied end up with a single atom

Individual Collisions

+ + =

+ + = +

Efficient Preparation

83%

T. Grünzweig, A. Hilliard, M. McGovern, M. F. A., Nature Physics 6, 951-954, 2010.

What is missing?

Detuning

Multi-level structure

Figure: Thad Walker

Conclusions• You CAN see a single atom in a microscope. • We can count several atoms in a microscopic

volume• Light assisted collisions can lead to only one

atom being lost• Investigating individual events reveal information

not available from ensemble average measurements

• We (and visitors) can (almost) deterministically prepare a single atom in an optical micro-trap

Acknowledgements

• NZ-FRST Contract No. NERF-UOOX0703

• UORG

• Professor Thad G Walker University of Wisconsin

• The team: Tzahi Grünzweig, Andrew Hilliard, Yin Fung, Alicia V. Carpentier, and Matt McGovern

Power

Power and Detuning