  A mesoscopic device in the simple tunnel junction or quantum point contact
geometry emits microwaves with remarkable quantum properties, when subjected to
a sinusoidal drive in the GHz range. In particular, single and two-photon
squeezing as well as entanglement in the frequency domain have been reported.
By revising the photo-assisted noise analysis developed in the framework of
electron quantum optics, we present a detailed comparison between the cosine
drive case and other experimentally relavent periodic voltages such as
rectangular and Lorentzian pulses. We show that the latter drive is the best
candidate in order to enhance quantum features and purity of the outgoing
single and two-photon states, a noteworthy result in a quantum information
perspective.
