Atomic, molecular and optical (AMO) physics at JQI investigates the ways in which light and matter interact at the scale of one or a few atoms, and how those interactions can be controlled.

Typically the work involves the isolation, capture, manipulation and measurement of atoms as they absorb and emit photons - the smallest units of light. Scientists use light sources of various frequencies, such as tiny lasers, along with magnetic and/or electrical fields, to slow and gradually immobilize the targets. JQI projects investigate individual neutral atoms, individual ions (atoms that have lost an electron, thus gaining a net positive charge), clusters of atoms in various conditions, superconducting devices and other objects to test theories and observe phenomena.

In general, the target atoms are extremely cold, some of them only a fraction of a millionth of a degree above absolute zero in a high-vacuum chamber. That not only makes them more controllable and easier to study, but it also isolates them from contact with their surroundings, which would destroy the quantum states.

The energies used to probe atoms are vanishingly small, which means the researchers must use instruments of exquisite sensitivity, such as detectors that can register the arrival of a single photon. Not surprisingly, much of this equipment must be custom-constructed and finely tuned.

JQI's AMO work takes many forms, in a constant interplay between theory and experiment. Some groups are studying the behavior of atoms that are colliding, or have been placed in an exotic condition called a "Bose-Einstein condensate."

Others are working on manipulating atoms that are caught in "optical lattices" - traps made of grid-like electromagnetic patterns produced by intersecting beams of light - or confined in minuscule cavities. Research teams are examining ways to induce and control entanglement between two objects held in optical traps and cavities, a critical necessity for eventual quantum computing. Because atoms cannot come into direct contact with their surroundings without destroying the superposition of states, entanglement will likely form the means of "wiring" quantum information units together into systems.

When quantum objects do encounter their environments, or are measured or otherwise tampered with, they lose the condition of superposition and take on specific properties - a process called "decoherence." That is, they become part of the everyday classical (i.e., non-quantum) world in which everything has definable characteristics. JQI scientists are observing and analyzing exactly what happens as decoherence occurs over small time intervals. This information will be important for devising and regulating quantum computers, among many other uses.