Quantum computation requires qubits that can be coupled in a scalable manner, together with universal and high-fidelity one- and two-qubit logic gates1, 2. Many physical realizations of qubits exist, including single photons3, trapped ions4, superconducting circuits5, single defects or atoms in diamond6, 7 and silicon8, and semiconductor quantum dots9, with single-qubit fidelities that exceed the stringent thresholds required for fault-tolerant quantum computing10. Despite this, high-fidelity two-qubit gates in the solid state that can be manufactured using standard lithographic techniques have so far been limited to superconducting qubits5, owing to the difficulties of coupling qubits and dephasing in semiconductor systems11, 12, 13. Here we present a two-qubit logic gate, which uses single spins in isotopically enriched silicon14 and is realized by performing single- and two-qubit operations in a quantum dot system using the exchange interaction, as envisaged in the Loss–DiVincenzo proposal2. We realize CNOT gates via controlled-phase operations combined with single-qubit operations. Direct gate-voltage control provides single-qubit addressability, together with a switchable exchange interaction that is used in the two-qubit controlled-phase gate. By independently reading out both qubits, we measure clear anticorrelations in the two-spin probabilities of the CNOT gate.
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- Supplementary Information (759 KB)
This file contains Supplementary Methods, Text and Data, Supplementary Figures 1-7 and Supplementary References.