High coherence 2D Kerr-cat qubit: Experimental realization and technical challenges (2/2)*

The Kerr-cat qubit is a bosonic qubit in which the information is encoded in multi-photon cat states. The suppressed bit flip rate makes this qubit a promising candidate to implement quantum error correction codes tailored for noise-biased qubits. Moreover, its intrinsic nonlinearities enable fast logic gates and QND measurement. However, the strong two-photon pump drive, which stabilizes the cat-state, introduces both theoretical and practical challenges when large cat sizes or multi-qubit operations are desired. Here, we present an experimental realization of high-coherence Kerr-cat qubits in a 2D superconducting circuit. With a novel on-chip filter significantly increasing the qubit-pump coupling, we can generate large cats with smaller drive power and explore the bit-flip dependence on the cat size. With bit-flip times approaching 800us for a cat of size 11 photon our work paves the way towards high-coherence and scalable multi-qubit devices. 

The talk is divided into two parts. This is the second part, which will discuss the fabrication, measurement, and experiment results