TY - JOUR T1 - Semiconductor double quantum dot micromaser JF - Science Y1 - 2015 A1 - Y. -Y. Liu A1 - J. Stehlik A1 - C. Eichler A1 - Michael Gullans A1 - J. M. Taylor A1 - J. R. Petta AB - The coherent generation of light, from masers to lasers, relies upon the specific structure of the individual emitters that lead to gain. Devices operating as lasers in the few-emitter limit provide opportunities for understanding quantum coherent phenomena, from THz sources to quantum communication. Here we demonstrate a maser that is driven by single electron tunneling events. Semiconductor double quantum dots (DQDs) serve as a gain medium and are placed inside of a high quality factor microwave cavity. We verify maser action by comparing the statistics of the emitted microwave field above and below the maser threshold. VL - 347 U4 - 285 - 287 UR - http://arxiv.org/abs/1507.06359v1 CP - 6219 J1 - Science U5 - 10.1126/science.aaa2501 ER -