Lasers locate trapped atoms

17 Jun 2002

Physicists at Yale University, US, are the first to create a "squeezed" state of atoms.

In a move that could dramatically improve precision measurement and navigation systems, Chad Orzel and colleagues at Yale University, US have developed a method to manipulate the quantum states of atoms,(see SCIENCE 291 2386-2389, 2001).

The scientists cooled a sample of rubidium atoms to near absolute zero to create a "Bose Eintstein condensate" (BEC), a collection of atoms that have collapsed into a single quantum state. They blasted the BEC with a trapping laser to form a "lattice of light" around it. By varying the laser's intensity, Orzel and his colleagues were able to shift the lattice in such a way that they created an array of potential wells. Increasing the laser's intensity further, forced the BEC into the wells.

It was at this point that Orzel and colleagues made their breakthrough. The researchers wanted to estimate how many atoms had been squeezed into each well. However the Heisenberg Uncertainty Principle states that it is impossible to know accurately the position and velocity of a particle. But, by manipulating the laser intensity and adjusting the interactions between the atoms, the scientists managed to reduce the quantum uncertainty of the number of atoms in a single well from ± 50 to ± 2 atoms.

"Quantum states of this type are called "squeezed states" and have been extensively studied in light," said Orzel. "This is the first time that anyone has seen the number-squeezing in atoms."

"Combining these states with techniques used in atom interferometry, we hope to increase the sensitivity of detectors for rotation and acceleration, and gradients in gravity," he added.