▎ 摘　　要

NOVELTY - Method for operating quantum network node (101) involves preparing the nuclear spin (108) in a preset nuclear-spin quantum state, subjecting the electron spin (106) to an entanglement protocol comprising multiple repetitions of an entanglement primitive (EP, EP1) for entangling with another quantum system, preferably another quantum network node, and performing operations on and/or readout of the data qubit state or causing entanglement between the data qubit state and a further quantum system, the electron spin host (105) occupies a wanted state of the electron spin host (NV-), and an unwanted state of the electron spin host (NV0), the wanted state is a wanted charge state and the unwanted state is an unwanted charge state, resetting a charge state (NV-, NV0) of the electron spin host from the unwanted charge state to the wanted charge state, and providing an average series electron spin value of the series of entanglement primitives. USE - Method for operating quantum network node such as multimode quantum network. ADVANTAGE - The charge state switching can be included in the entanglement protocol and the data qubit can still be used with acceptable fidelity. Thus, effects of ionization of the electron spin host on the qubit are mitigated. The reset preserves the quantum state of the nuclear spin with high quality. The fidelity loss for the qubits due to the reset is less than 5%, less than 1% is desirable and considered presently achievable, even lower losses such as 0,1% are preferred and are expected to be feasible. Dephasing of the quits during evolution in the unwanted state can be reduced or removed by controlled provision of an average phase evolution on nuclear spin in the desired state. DETAILED DESCRIPTION - Method for operating quantum network node (101) involves preparing the nuclear spin (108) in a preset nuclear-spin quantum state, subjecting the electron spin (106) to an entanglement protocol comprising multiple repetitions of an entanglement primitive (EP, EP1) for entangling with another quantum system, preferably another quantum network node, performing operations on and/or readout of the data qubit state or causing entanglement between the data qubit state and a further quantum system, the electron spin host (105) occupies a wanted state of the electron spin host (NV-), and an unwanted state of the electron spin host (NV0), the wanted state is a wanted charge state and the unwanted state is an unwanted charge state, resetting a charge state (NV-, NV0) of the electron spin host from the unwanted charge state to the wanted charge state, and/or determining an average unwanted state electron spin value of the electron spin when the electron spin host is in the unwanted state of the electron spin host (NV0), and varying electron spin states (ms = -1 , 0, +1 ) in a series of the entanglement primitives (EP1), providing an average series electron spin value of the series of entanglement primitives in accordance with the average unwanted state electron spin value, preferably matching the average unwanted state electron spin value. The node comprises a wide-bandgap solid state material (103) comprising at least one electron spin host providing an electron spin for a communication qubit and at least one nuclear spin host (107) providing a nuclear spin for a data qubit, the electron spin and the nuclear spin is magnetically coupled. INDEPENDENT CLAIMS are included for the following: ystem (100) for operating a quantum memory or quantum network node; computer program product; and computer readable medium. DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the system. 100System 101Quantum network node 103Solid-state material 105Electron spin host 106Electron spin 107Nuclear spin host 108Nuclear spin