Realizing highly entangled states in asymmetrically coupled three NV centers at room temperature

Despite numerous efforts the coupling between randomly arranged multi-NV centers and also resonators has not been improved significantly mainly due to our limited knowledge of their entanglement times 2t_ent. Here, we demonstrate a very strong coupling between three-NV centers by using a simulated triple electron-electron resonance experiment based on a new quantum U_C gate on IBM quantum simulator with 2t_ent 12.5 microsecond arranged is a triangular configuration. Interestingly through breaking the symmetry of couplings an even lower 2t_ent 6.3 μs can be achieved. This simulation not only explains the luminescence spectra in recently observed three-NV centers [Haruyama, Nat. Commun. 2019] but also shows a large improvement of the entanglement in artificially created structures through a cyclic redistribution of couplings. Realistically disordered coupling configurations of NV centers qubits with short time periods and high (0.89-0.99) fidelity of states clearly demonstrate possibility of accurate quantum registers operated at room temperature.