Multiphoton processes in driven mesoscopic systems

We study the statistics of multiphoton absorption/emission processes in a mesoscopic ring threaded by a harmonic time-dependent flux Φ(t) . For this sake, we demonstrate a useful analogy between the Keldysh quantum kinetic equation for the electron distribution function and a continuous time random walk in energy space with corrections due to interference effects. Studying the probability to absorb/emit n quanta ℏω per scattering event, we explore the crossover between ultraquantum/low-intensity limit and quasiclassical/high-intensity regime, and the role of multiphoton processes in driving it.