A four-qubit germanium quantum processor

Nature, Published online: 24 March 2021; doi:10.1038/s41586-021-03332-6

Using germanium quantum dots, a four-qubit processor capable of single-, two-, three-, and four-qubit gates, demonstrated by the creation of four-qubit Greenberger−Horne−Zeilinger states, is the largest yet realized with solid-state electron spins.