All-Optical Quantum Dot Switch (IMAGE) Joint Quantum Institute Caption This is the setup of a waveguide made from a photonic crystal. A quantum dot (QD) is placed inside a tiny zone (cavity) clear of holes. Light is sent into and out of the waveguide via endcaps (the semi-circular structure at both ends, indicated by green arrows). If properly timed (the synchronicity time, tau, being less than about 100 ps), a pump (control) laser pulse will allow an accompanying probe pulse to exit out the side. If the probe and pump beams are not aligned, the probe beam will exit out the far end of the waveguide. Credit Ranojoy Bose, JQI Usage Restrictions Please credit Joint Quantum Institute License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.