[Professor Andrea Morello of UNSW, who led the work] et al achieved 1-qubit operation fidelities up to 99.95 percent, and 2-qubit fidelity of 99.37 percent with a three-qubit system comprising an electron and two phosphorous atoms, introduced in silicon via ion implantation. A Delft team in the Netherlands led by Lieven Vandersypen achieved 99.87 percent 1-qubit and 99.65 percent 2-qubit fidelities using electron spins in quantum dots formed in a stack of silicon and silicon-germanium alloy (Si/SiGe). A RIKEN team in Japan led by Seigo Tarucha similarly achieved 99.84 percent 1-qubit and 99.51 percent 2-qubit fidelities in a two-electron system using Si/SiGe quantum dots.
The UNSW and Delft teams certified the performance of their quantum processors using a sophisticated method called gate set tomography, developed at Sandia National Laboratories in the U.S. and made openly available to the research community. Morello had previously demonstrated that he could preserve quantum information in silicon for 35 seconds, due to the extreme isolation of nuclear spins from their environment. But the trade-off was that isolating the qubits made it seemingly impossible for them to interact with each other, as necessary to perform actual computations. Today’s paper describes how his team overcame this problem by using an electron encompassing two nuclei of phosphorus atoms. The three papers from the UNSW team, Delft team and RIKEN group in Tokyo can be found at their respective links.
