A coherent perfect absorber for matter waves

Coherent perfect absorption (CPA), i.e. the complete extinction of bidirectional incoming radiation by a complex potential in a wave- guiding medium, is an effect that relies on the destructive interference of reflected and transmitted waves. It has been observed in many different linear systems like for example for light interacting with absorbing scatterers or for sound waves. Extending the concept of CPA to non-linear systems we find that the conditions for CPA can be achieved easier than in the linear case since localised absorption in a non-linear medium stabilises the system. We experimentally demonstrate CPA for matter waves with an atomic Bose-Einstein condensate in a one-dimensional optical lattice with an absorptive site where the absorption is introduced by an electron beam.