Lasing in a coupled hybrid double quantum dot-resonator system

Abstract

We theoretically investigate the possibility of lasing in an electromagnetic resonator coupled to a voltage-biased hybrid-double-quantum-dot comprised of a double-quantum-dot tunnel coupled simultaneously to a normal metal and a superconducting lead. Using a unitary transformation, we derive a resonator-double-quantum-dot interaction Hamiltonian in the rotating wave approximation which reveals the fact that lasing in this system is mediated by electron transitions between Andreev energy levels in the system's density of states. Moreover, by employing a markovian master equation incorporating dissipation effects for the electronic and photonic degrees of freedom, we numerically calculate the steady-state reduced density-matrix of the system from which we determine the average photon number and its statistics in the resonator in various parameter regimes. We find that at some appropriate parameter configurations, lasing can be considerably enhanced due to the possiblity of electron tansitions between multiple Andreev levels in the system.

Plasmon Squeezing in Single-Molecule Junctions

“…When the plasmon is excited solely by inelastic tunneling electrons ( g 0 ≠ 0 and E L = 0), ⟨ a 0 ⟩ = 0 and ⟨ a 0 2 ⟩ = 0, such that ⟨ Δx 2 ⟩ = ⟨ Δp 2 ⟩ = (1/2) + ⟨ a 0 † a 0 ⟩ ≥ (1/2), squeezing is not possible. Actually, this is the standard model of a two-level molecule coupling to one bosonic mode, which has been studied intensively. − When the plasmon mode is excited only by the laser field ( g 0 = 0 and E L ≠ 0), ⟨ Δx 2 ⟩ = ⟨ Δp 2 ⟩ = (1/2) because the plasmon mode is in the coherent state. Thus, squeezing cannot be achieved when there is only one drive.…”