A ‘quantum eraser’ that can prevent or allow absorption of an entangled remotely located photon has been demonstrated by a Singapore–European collaboration of scientists. Charles Altuzarra and co-workers use the phenomenon of coherent perfect absorption in a thin plasmonic metamaterial that is placed inside an interferometer to perform the experiment. A pair of polarization-entangled photons is first produced by spontaneous parametric down-conversion in a 2-mm-thick nonlinear crystal of beta-barium borate (BBO) that is illuminated with 405 nm light from a 200 mW laser diode. One of the entangled photons (named the idler) passes through a polarizer to a photodectector, while the other (the signal) enters the interferometer that has a beamsplitter and photodetector either side of the metamaterial. Controlling the polarization of the idler photon can switch the metamaterial between regimes of travelling-wave absorption and coherent absorption.