Strongly correlated photonic materials: parametric interactions and ultrastrong coupling in circuit QED

Wenjuan Yang, Xiang‐Bin Wang

Xiao‐Ming Zhang, Guang-Fei Yang, Xin-Ding Zhang

Alicia J. Kollár

Federico Armata, Giuseppe Calajò, Tuomas Jaako +2 more

We analyze a multi-qubit circuit QED system in the regime where the qubit-photon coupling dominates over the system's bare energy scales. Under such conditions a manifold of low-energy states with a high degree of entanglement emerges. Here we describe a time-dependent protocol for extracting these quantum correlations and converting them into well-defined multi-partite entangled states of non-interacting qubits. Based on a combination of various ultrastrong-coupling effects the protocol can be operated in a fast and robust manner, while still being consistent with experimental constraints on switching times and typical energy scales encountered in superconducting circuits. Therefore, our scheme can serve as a probe for otherwise inaccessible correlations in strongly-coupled circuit QED systems. It also shows how such correlations can potentially be exploited as a resource for entanglement-based applications.

Federico Armata, Giuseppe Calajò, Tuomas Jaako +2 more

We analyze a multiqubit circuit QED system in the regime where the qubit-photon coupling dominates over the system's bare energy scales. Under such conditions a manifold of low-energy states with a high degree of entanglement emerges. Here we describe a time-dependent protocol for extracting these quantum correlations and converting them into well-defined multipartite entangled states of noninteracting qubits. Based on a combination of various ultrastrong-coupling effects, the protocol can be operated in a fast and robust manner, while still being consistent with experimental constraints on switching times and typical energy scales encountered in superconducting circuits. Therefore, our scheme can serve as a probe for otherwise inaccessible correlations in strongly coupled circuit QED systems. It also shows how such correlations can potentially be exploited as a resource for entanglement-based applications.

Iacopo Carusotto, Andrew Houck, Alicia J. Kollár +3 more