Hybrid systems of boron vacancy centers coupled to flux qubits and applications

Abstract The negatively charged boron vacancy center ( V B − ) in a hexagonal boron nitride ( h -BN) film, represents a promising quantum unit at room temperature due to its exceptional attributes, including remarkable sensitivity to magnetic field or strain, long coherence time, nearly perfect spin homogeneity, and an ultra-thin film structure. We here study a different hybridization proposal of an ensemble of V B − centres magnetically coupled to a superconducting flux qubit (FQ) or a DC superconducting quantum interference device (SQUID). Because the localization degree and density of the magnetic field in the FQ are much greater than that of the superconducting resonator (SR), this type of spins-FQ coupling is much stronger for an identical number of V B − centres, and it can therefore mimic the traditional light–matter interactions, i.e., the Dicke-, Tavis-Cummings- or Rabi-like model. For applications, this hybrid quantum system can potentially guarantee such as the simulation of quantum phase transitions (QPTs) of the anomalous Rabi-like model especially showing the influences to QPTs of the spins’ dephasing and FQ’s decay, criticality-enhanced quantum metrology or quantum sensing, the steady-state preparation of single- and two-mode spin-squeezed state (SSS). This investigation can potentially provide a platform for the subsequent quantum information processing (QIP).