We study a model which can describe a superconducting single electron transistor (SSET) or a double quantum dot coupled to transmission-line oscillator. In both cases the degree of freedom is given by a charged particle, which couples strongly to the
electromagnetic environment or phonons. We consider the case where a lasing condition is established and study the dependence of the average photon number in the resonator on the spectral function of the electromagnetic environment. We focus on three important cases: a strongly coupled environment with a small cut-off frequency, a structured environment peaked at a specific frequency and 1/f-noise. We find that the electromagnetic environment can have a substantial impact on the photon creation. Resonance peaks are in general broadened and additional resonances can appear.
We propose a setup for a quantitative test of the quantum fluctuation theorem. It consists of a quantum conductor, driven by an external voltage source, and a classical inductor-capacitor circuit. The work done on the system by the voltage source can
be expressed by the classical degrees of freedom of the LC circuit, which are measurable by conventional techniques. In this way the circuit acts as a classical detector to perform measurements of the quantum conductor. We prove that this definition is consistent with the work fluctuation theorem. The system under consideration is effectively described by a Langevin equation with non-Gaussian white noise. Our analysis extends the proof of the fluctuation theorem to this situation.
We study the photon generation in a transmission line oscillator coupled to a driven qubit in the presence of a dissipative electromagnetic environment. It has been demonstrated previously that a population inversion in the qubit may lead to a lasing
state of the oscillator. Here we show that the circuit can also exhibit the effect of lasing without inversion. This is possible since the coupling to the dissipative environment enhances photon emission as compared to absorption, similar to the recoil effect which was predicted for atomic systems. While the recoil effect is very weak, and so far elusive, the effect described here should be observable with present circuits. We analyze the requirements for the system parameters and environment.
