Plasmons that won't stick

All fundamental particles in nature can be divided into two classes: bosons and fermions. One of the first things taught in quantum mechanics courses is that bosons are allowed to occupy the same quantum state, but fermions are not. In other words, identical bosons are allowed to “stick” together, but fermions will be forced apart. On page 1373 of this issue, Vest et al. (1) overturn the common wisdom that identical bosons, when forced together, will tend to bunch. The bosons they studied, surface plasmon polaritons (SPPs), are coupled together in a lossy environment—one in which they can only propagate for short distances. It is this loss process that allows the authors to precisely tailor the quantum interaction and observe antibunching.