Amplification of the Schrodinger's Cat by Superposing Two Kitten States in Coupled Waveguides

The optical Schrodinger's cat is a crucial quantum resource for quantum computation and quantum metrology. The amplitude of cat states is desired to be as high as possible to achieve a good performance in these processes. Here, we demonstrate the amplification of cat states by superposing two kitten states in coupled waveguides. First, we propose a mechanism of two kitten states' superposition. Initially, two nearby coherent state components that participate in the superposition interfere, resulting in a coherent-like state. Then, the superposition of two such coherent-like states creates a cat-like state. Depending on the different regions of the superposition coefficients, the amplitude of the cat-like state may be larger, smaller, or intermediate compared to the amplitudes of the initial kitten states. Next, based on the above mechanism, we theoretically demonstrate the superposition of two cat states in coupled waveguides via quantum beam splitting process and conditional measurement. Consequently, we achieve an amplification of cat states beyond √(α² +β² ) with high fidelity and success probability, given that the input kitten states have amplitudes α and β respectively. The proposed mechanism can be extended to amplify other macroscopic quantum states and our scheme can be implemented on chips to provide high-quality cat states for future quantum information tasks.