Tomography of entangling two-qubit logic operations in exchange-coupled donor electron spin qubits

Abstract

Scalable quantum processors require high-fidelity universal quantum logic operations in a manufacturable physical platform. Donors in silicon provide atomic size, excellent quantum coherence and compatibility with standard semiconductor processing, but no entanglement between donor-bound electron spins has been demonstrated to date. Here we present the experimental demonstration and tomography of universal 1- and 2-qubit gates in a system of two weakly exchange-coupled electrons, bound to single phosphorus donors introduced in silicon by ion implantation. We surprisingly observe that the exchange interaction has no effect on the qubit coherence. We quantify the fidelity of the quantum operations using gate set tomography (GST), and we use the universal gate set to create entangled Bell states of the electrons spins, with fidelity ~ 93%, and concurrence 0.91 +/- 0.08. These results form the necessary basis for scaling up donor-based quantum computers.

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• Comparing Schemes for Creating Qudit Graph States from 16- & 128-dimensional Hilbert Space using Donors in Silicon
• Theory of Electron Spin Resonance Scanning Tunneling Microscopy: The First Decade
• Coupling a ${}^{73}$Ge nuclear spin to an electrostatically defined quantum dot
• Near-deterministic photon entanglement from a spin qudit in silicon using third quantisation
• Electron readout contrast enhancement in the parallel nuclear regime of an exchange-coupled donor spin qubit system