Sign-changing photon-mediated atom interactions in multimode cavity QED

Understand

Sign-changing interactions constitute a crucial ingredient in the creation of frustrated many-body systems such as spin glasses.

• We present here the demonstration of a photon-mediated sign-changing interaction between Bose-Einstein condensed (BEC) atoms in a confocal cavity.
• The interaction between two atoms is of an unusual, nonlocal form proportional to the cosine of the inner product of the atoms' position vectors.
• This interaction arises from the differing Gouy phase shifts of the cavity's degenerate modes.