Lasing and transport in a quantum-dot resonator circuit

We study a double quantum-dot system coherently coupled to an electromagnetic resonator. A current through the dot system can create a population inversion in the dot levels and, within a narrow resonance window, a lasing state in the resonator. The lasing state correlates with the transport properties. On one hand, this allows probing the lasing state via a current measurement. On the other hand, the resulting narrow current peak allows resolving small differences in the dot properties (e.g., a small difference in the Zeeman splittings of the two dots). For realistic situations relaxation processes have pronounced consequences. Remarkably, they may even enhance the resolution between different spin states by releasing a trapped population in the off-resonant spin channel.