An 11-qubit atom processor in silicon
Hermann Edlbauer, Junliang Wang, A. M. Saffat‐Ee Huq, Ian Thorvaldson, Michael T. Jones, S. H. Misha, William J. Pappas, Christian M. Moehle, Yu‐Ling Hsueh, Henric Bornemann, S. K. Gorman, Yousun Chung, J. G. Keizer, Ludwik Kranz, M. Y. Simmons
Abstract
Abstract Phosphorus atoms in silicon represent a promising platform for quantum computing, as their nuclear spins exhibit coherence times over seconds 1,2 with high-fidelity readout and single-qubit control 3 . By placing several phosphorus atoms within a radius of a few nanometres, they couple by means of the hyperfine interaction to a single, shared electron. Such a nuclear spin register enables high-fidelity multi-qubit control 4 and the execution of small-scale quantum algorithms 5 . An important requirement for scaling up is the ability to extend high-fidelity entanglement non-locally across several spin registers. Here we address this challenge with an 11-qubit atom processor composed of two multi-nuclear spin registers that are linked by means of electron exchange interaction. Through the advancement of calibration and control protocols, we achieve single-qubit and multi-qubit gates with all fidelities ranging from 99.10% to 99.99%. By entangling all combinations of local and non-local nuclear-spin pairs, we map out the performance of the processor and achieve state-of-the-art Bell-state fidelities of up to 99.5%. We then generate Greenberger–Horne–Zeilinger (GHZ) states with an increasing number of qubits and show entanglement of up to eight nuclear spins. By establishing high-fidelity operation across interconnected nuclear spin registers, we realize a key milestone towards fault-tolerant quantum computation with atom processors.