Efficient generation of arbitrary Fock-state superpositions in a superconducting cavity

In this talk, I will discuss our experimental demonstration of an efficient method to generate arbitrary Fock-state superpositions in a superconducting quantum circuit, where a qubit is dispersively coupled to a microwave cavity mode without the need of fine-frequency tuning. Compared with the previous multi-step state-synthesis schemes, our method requires only a single step of unitary evolution and measurement-based post-selection, and thus is more robust to noise and accumulation of experimental errors. Using the method, we experimentally generate high-fidelity phase eigenstates under various Hilbert-space dimensions and squeezed states, which are useful for quantum walk and high-precision measurements.