SIMULTANEOUS 4TH-ORDER SQUEEZING OF BOTH QUADRATURE COMPONENTS

It is shown that a particular combination of so-called even coherent states, dubbed the orthogonal-even coherent state, while exhibiting no ''ordinary'' or second-order squeezing, can furnish near-optimal simultaneous-quadrature fourth-order squeezing [where the latter term is defined in the sense of Hong and Mandel, Phys. Rev. Lett. 54, 323 (1985)]. The Wigner function of the particular quantum-mechanical superposition of states is calculated and various plots compared to the Wigner function of a simple statistical mixture of the same states. Rather uninteresting behavior is found in the latter case, which illustrates that the higher-order squeezing effect is due to nonclassical, quantum-mechanical ''interference in phase space.''