Experimental preparation of generalized cat states for itinerant microwave photons

TL;DR

This paper demonstrates a method to generate and verify generalized cat states of microwave photons using superconducting qubits, enabling advanced quantum information processing with controllable superpositions.

Contribution

A versatile approach for creating and controlling generalized itinerant cat states in the microwave domain using superconducting qubits is introduced.

Findings

Successful creation of generalized cat states verified via quantum state tomography.

Observation of fourth-order squeezing in the prepared states.

Quantification of quantum coherence demonstrates high control over superpositions.

Abstract

Generalized cat states represent arbitrary superpositions of coherent states, which are of great importance in various quantum information processing protocols. Here we demonstrate a versatile approach to creating generalized itinerant cat states in the microwave domain, by reflecting coherent state photons from a microwave cavity containing a superconducting qubit. We show that, with a coherent control of the qubit state, a full control over the coherent state superposition can be realized. The prepared cat states are verified through quantum state tomography of the qubit state dependent reflection photon field. We further quantify quantum coherence in the prepared cat states based on the resource theory, revealing a good experimental control on the coherent state superpositions. The photon number statistic and the squeezing properties are also analyzed. Remarkably, fourth-order squeezing is observed in the experimental states. Those results open up new possibilities of applying generalized cat states for the purpose of quantum information processing.