Our atom interferometers use laser light to prepare the internal and motional states of a cloud of rubidium atoms. Next, the light splits the atomic wavefunction so that it propagates along two separated paths, before recombining these with a phase difference , much as light waves are split and recombined in a conventional Mach-Zehnder interferometer. 

We use fluorescence detection to measure the final populations of two hyperfine ground states, which are given by and , as a result of quantum interference. If the atom is accelerated – for example by gravity or some other small force – this produces a shift of the phase . The conversion from phase shift to acceleration depends only on the wavelength of the laser light and on the timing of the light pulses. These are both very accurate and stable, so this device measures acceleration much more reliably than the best conventional accelerometers. It can also be extremely sensitive – for example the instrument in our laboratory can sense changes of a few billionths of the acceleration due to gravity.

One main line of this research is to apply that sensitivity and accuracy to enable navigation without the use of eternal signals such as Sonar or Satellite communications. To do this we need to very accurately measure accelerations. Then by integrating this signal twice we can determine our position with both high accuracy and precision. 

This will enable vehicles to navigate without the need to communicate with external sources like GPS.

For more information please contact j.cotter@imperial.ac.uk

Some information about our previous cold atom experiments can be found in the links below:

• Cavity QED
• Magneto Optical Traps Integrated into Atom Chips
• BEC Physics and Atom Interferometry
• Integrated Waveguide Atom Chip