E. A. Hinds

Deflection of an atomic beam by the Casimir force

The force experienced by an atom inside a parallel‐plate waveguide is one of the basic phenomena of cavity QED. The full QED expression for this force is a complicated function, which depends upon the atomic oscillator strengths, the position of the atom, and the width of the cavity. For ground‐state atoms one can distinguish two simple limits. (i) When the gap is sufficiently small, the force takes on the form of a van der Waals interaction between the instantaneous electric dipole of the atom and its multiple images in the walls of the waveguide. (ii) In a large gap, when the atom is far from the walls, the van der Waals force is suppressed and the main force predicted by theory is due to the Casimir interaction of the atom with the cavity vacuum field. Whereas the van der Waals force between atoms and conductors has previously been studied experimentally, the Casimir force has not. Here we report the first observation of atom deflection by the Casimir force.

Observation and measurement of the Casimir‐Polder force

We have studied the deflection of ground‐state sodium atoms passing through a micron‐sized parallel‐plate cavity by measuring the intensity of a sodium atomic beam transmitted through the cavity as a function of the plate separation. This experiment provides clear evidence for the existence of the Casimir‐Polder force, which is due to modification of the ground state Lamb shift in the confined space of a cavity. Our results confirm the magnitude of the force and the distance‐dependence predicted by quantum electrodynamics.

Measurement of the van der Waals interaction between an atom and a cavity

We have measured the energy of interaction between a sodium atom and its electrical images in the walls of a micron‐sized cavity. The atoms are centrally located between two plane parallel gold mirrors whose separation is varied from 500 nm to 2400 nm. In the smallest cavities, the atoms are held near the center by means of a one‐dimensional optical dipole trap. Energy level shifts are measured directly by laser spectroscopy of the states nS with n in the range 10–13. This cavity QED study provides the first direct, quantitative test of the Lennard‐Jones–van der Waals interaction as a function of controlled atom‐surface separation and mean square electric dipole moment.

Atomic Physics in Confined Space: Suppressing Spontaneous Emission at Optical Frequencies and Measuring the Van der Waals Atom-Surface Interaction

The radiative properties of an atomic system depend upon the structure of the vacuum field in the surrounding space. By confining the atoms in cavities in which the mode distribution of the field is very different from its free space configuration, it is possible to strongly alter the atomic spontaneous radiation rates and transition frequencies. These Cavity Quantum Electrodynamics effects, as they are called, have been first demonstrated in the microwave domain CI] and begin now to be observed in the optical domain [2–3]. Interest in these studies is manifold. First, the quantum noise of the electromagnetic field is a basic limitation to the precision of any optical experiment. Understanding how this noise is altered in a cavity is very important in order to analyze the ultimate precision of experiments on quantum radiators placed in the vicinity of metallic boundaries [4]. Being able to suppress spontaneous emission and to prepare quasi infinitely long-lived atomic excited states is a possibility which is certainly worth considering for ultra high resolution spectroscopy experiments. At a more applied level, measuring atomic radiative rates and transition frequencies in a small metallic structure is a new way of performing atom-surface physics. By analyzing the perturbations of the atomic radiative properties, one might get useful information on the electronic properties of the metal surfaces...