  The optical cat state, known as the superposition of coherent states, has
broad applications in quantum computation and quantum metrology. Increasing the
number of optical cat states is crucial to implement complex quantum
information tasks based on them. Here, we prepare two optical cat states
simultaneously based on a nondegenerate optical parametric amplifier. By
subtracting one photon from each of two squeezed vacuum states, two odd cat
states with orthogonal superposition direction in phase space are prepared
simultaneously, which have similar fidelity of 60% and amplitude of 1.2.
Compared with the traditional method to generate two odd optical cat states
based on two degenerate optical parametric amplifiers, only one nondegenerate
optical parametric amplifier is applied in our experiment, which saves half of
the quantum resource of nonlinear cavities. The presented results make a step
toward preparing the four-component cat state, which has potential applications
in fault-tolerant quantum computation.
