Controllable generation of highly nonclassical states from nearly pure squeezed vacua

摘要

We present controllable generation of various kinds of highly nonclassicalstates of light, including the single photon state and superposition states ofmesoscopically distinct components. The high nonclassicality of the generatedstates is measured by the negativity of the Wigner function, which is largestever observed to our knowledge. Our scheme is based on photon subtraction froma nearly pure squeezed vacuum, generated from an optical parametric oscillatorwith a periodically-poled KTiOPO$_4$ crystal as a nonlinear medium. This is animportant step to realize basic elements of universal quantum gates, and toserve as a highly nonclassical input probe for spectroscopy and the study ofquantum memory.