Multicomponent cat states with sub-Planck structures and their optomechanical analogues

Abstract: We investigate the superposition of coherent states, emphasizing quantum states with distinct Wigner phase-space features relevant to quantum information applications. In this study, we introduce generalized versions of the compass state, which display enhanced phase-space characteristics compared to the conventional compass state, typically a superposition of four coherent states. Our findings reveal that, unlike sub-Planck structures and phase-space sensitivity of the compass state, these generalized states produce isotropic sub-Planck structures and sensitivity to phase-space displacements. We demonstrate that these desirable phase-space characteristics are maintained in superpositions comprising at least six distinct coherent states. Furthermore, we show that increasing the number of coherent states in the superposition preserves these characteristics, provided the number remains even. Finally, we examine an optomechanical system capable of generating the proposed quantum states, resulting in optomechanical counterparts with nearly identical phase-space structures, thereby suggesting the feasibility of physically realizing these generalized compass states.