Coherent population transfer in an atom by multiphoton adiabatic rapid passage.

Coherent population transfer in an atom using a sequence of adiabatic rapid passages through single-photon resonances is well-known, but it requires that the frequency sweep match the changing frequencies of the atomic transitions. The same population transfer can be effected via a single multiphoton adiabatic rapid passage, which requires only a small frequency sweep, if it is possible to select the desired multiphoton transition from the many possible transitions. Here we report the observation of population transfer between Rydberg states by high order multiphoton adiabatic rapid passage.

Microwave manipulation of an atomic electron in a classical orbit.

Although an atom is a manifestly quantum mechanical system, the electron in an atom can be made to move in a classical orbit almost indefinitely if it is exposed to a weak microwave field oscillating at its orbital frequency. The field effectively tethers the electron, phase-locking its motion to the oscillating microwave field. By exploiting this phase-locking, we have sped up or slowed down the orbital motion of the electron in excited lithium atoms by increasing or decreasing the microwave frequency between 13 and 19 gigahertz; the binding energy and orbital size change concurrently.