: The Casimir effect
describes unusual quantum behavior that creates a force between two neutral metal plates when they are held close together in a vacuum. The Casimir–Polder force describes a similar effect between a neutral metal plate and a single atom. While it is not easy to measure the strength of the Casimir effect, it is significantly harder to measure that of the Casimir–Polder force because the single atom involved is more easily affected by other quantum effects. Now, a group of researchers has developed a technique for measuring the strength of the force by manipulating the ability of light to attract and repel Bose–Einstein condensates
(BECs). The researchers placed a metal grate over a glass surface and shined a light into the glass at an angle such that all of the light was reflected but the light's electric field created oscillations in the metal grate. The shape of the grate resulted in resonance effects that created light fields in the gaps of the grate, which repelled the atoms in the BEC. That caused the atoms to fall toward the metal of the grate because of the attraction of the Casimir–Polder force and then bounce off the surface. The researchers were then able to measure the interference pattern within the BEC and use that to calculate the magnitude of the Casimir–Polder force's acceleration.