Quantum beat laser as a source of nonclassical wave–particle complementarity.

Quantum decoherence tends to bring about the quantum-to-classical transition via the system–reservoir interaction, which is the main obstacle to the realization of quantum information processing. We propose a scheme to unconditionally create the quantum light source satisfying the nonclassical wave–particle complementary relation in the framework of the quantum theory of second-order coherence. The scheme uses the efficient and controllable two-mode squeezed vacuum reservoir coupled to the combination modes of interest rather than the original cavity modes in the two-level quantum beat laser. We investigate the complementarity of the generated two-mode squeezed state including the dependencies of the visibility and which-path information on the ratio of detuning and decay rate. The visibility is shown to be larger than unity, different from the vanishing which-path information. The resultant complementary reaches the quantum regime without any classical analogue. [ABSTRACT FROM AUTHOR]