Large-Scale Schr\"odinger-Cat States and Majorana Bound States in Coupled Circuit-QED Systems

TL;DR

This paper explores large-scale Schr"odinger-cat states and Majorana bound states in coupled circuit-QED systems, revealing their entanglement properties, topological protection, and potential for coherent manipulation.

Contribution

It demonstrates the existence of large-scale Schr"odinger-cat states equivalent to Majorana bound states in circuit-QED chains, with implications for protected quantum information.

Findings

Ground states are Schr"odinger cat states with maximal entanglement.

States are mathematically equivalent to Majorana bound states.

System allows coherent probing and manipulation of the states.

Abstract

We have studied the low-lying excitations of a chain of coupled circuit-QED systems, and report several intriguing properties of its two nearly degenerate ground states. The ground states are Schr\"odinger cat states at a truly large scale, involving maximal entanglement between the resonator and the qubit, and are mathematically equivalent to Majorana bound states. With a suitable design of physical qubits, they are protected against local fluctuations and constitute a non-local qubit. Further, they can be probed and manipulated coherently by attaching an empty resonator to one end of the circuit-QED chain.