Collective Phenomena on Superconducting Qubits: Synchronization, Subradiance, and Entanglement Generation

Trabajo presentado en el WE-Heraeus-Seminar (Collective Effects and Non‐Equilibrium Quantum Dynamics 2021), celebrado del 28 al 30 de junio de 2021.A common environment acting on a pair of qubits gives rise to a plethora of different collective phenomena, such as the generation of qubit–qubit entanglement, quantum synchronization, and subradiance. Here, we introduce time-independent figures of merit for entanglement generation, quantum synchronization, and subradiance, and we perform an extensive analytical and numerical study of their dependence on the model parameters; we show that all these effects share a common cause, namely the action of the common bath, and yet may display opposite behaviors in certain regimes. We also address a recently proposed measure of the collectiveness of the dynamics driven by the bath, and we find that it almost perfectly witnesses the behavior of entanglement generation. Our results show that synchronization and subradiance can be employed as reliable local signatures of an entangling common bath in a broad scenario. Finally, we propose an experimental implementation of the model based on two transmon qubits capacitively coupled to a common resistor, which mimics the dynamics of several light-matter interaction systems, and provides a versatile quantum simulation platform of the open system in any collective regime [1]