Optical control of levitated nanoparticles via dipole–dipole interaction

We propose a scheme to create and unidirectionally transport thermal squeezed states and random-phase coherent states in a system of two interacting levitated nanoparticles. In this coupled levitated system, we create a thermal squeezed state of motion in one of the nanoparticles by parametrically driving it and then transporting the state to the other nanoparticle by making use of a unidirectional transport mechanism. This mechanism is based on inducing a nonreciprocal type of coupling in the system by suitably modulating the phases of the trapping lasers and the interparticle distance between the levitated nanoparticles. A nonreciprocal coupling creates a unidirectional channel where energy flows from one nanoparticle to the other nanoparticle but not vice versa, thereby allowing for the transport of mechanical states between the nanoparticles. We also affirm this unidirectional transport mechanism by creating and efficiently transporting a random-phase coherent state in the coupled levitated system. In both instances of mechanical state transport, the final nanoparticle showed similar characteristics to the original nanoparticle, depicting a high-fidelity unidirectional transport mechanism. Further, we make use of the feedback nonlinearity and parametric driving to create simultaneous bistability in the coupled levitated system also via this unidirectional mechanism. Our results may have potential applications in tunable sensing, metrology, quantum networks, and in exploring many-body physics under a controlled environment.