Magnetic-free polarization rotation in an atomic vapor cell.

Magnetic-free nonreciprocal optical devices have attracted great attention in recent years. Here, we investigated the magnetic-free polarization rotation of light in an atom vapor cell. Two mechanisms of magnetic-free nonreciprocity have been realized in ensembles of hot atoms, including electromagnetically induced transparency and optically-induced magnetization. For a linearly polarized input probe light, a rotation angle up to 86.4° has been realized with external control and pump laser powers of 10 mW and is mainly attributed to the optically-induced magnetization effect. Our demonstration offers a new approach to realize nonreciprocal devices, which can be applied to solid-state atom ensembles and may be useful in photonic integrated circuits.

Strong mechanical squeezing in an electromechanical system.

The mechanical squeezing can be used to explore quantum behavior in macroscopic system and realize precision measurement. Here we present a potentially practical method for generating strong squeezing of the mechanical oscillator in an electromechanical system. Through the Coulomb interaction between a charged mechanical oscillator and two fixed charged bodies, we engineer a quadratic electromechanical Hamiltonian for the vibration mode of mechanical oscillator. We show that the strong position squeezing would be obtained on the currently available experimental technologies.