They demonstrated on a 300 mm pre-industrial platform a new level of isotopic purification in a film deposited by chemical vapor deposition (CVD). This enables creating qubits in thin layers of silicon using a very high purity silicon isotope, 28Si, which produces a crystalline quality comparable to thin films usually made of natural silicon.
"Using the isotope 28Si instead of natural silicon is crucial for the optimization of the fidelity of the silicon spin qubit," said Marc Sanquer, a research director at Inac. "The fidelity of the spin qubit is limited to small values by the presence of nuclear spins in natural silicon. But spin qubit fidelity is greatly enhanced by using 28Si, which has zero nuclear spin. We expect to confirm this with qubits fabricated in a pre-industrial CMOS platform at CEA-Leti."