Universal high-fidelity quantum gates for spin qubits in diamond
Hanna Bartling, J. Yun, Kai-Niklas Schymik, M. van Riggelen, Luc Enthoven, Hendrik Benjamin van Ommen, Masoud Babaie, Fabio Sebastiano, Matthew Markham, D. J. Twitchen, T. H. Taminiau
Abstract
Spins associated to solid-state color centers are a promising platform for investigating quantum computation and quantum networks. Recent experiments have demonstrated multiqubit quantum processors, optical interconnects, and basic quantum error-correction protocols. One of the key open challenges towards larger-scale systems is to realize high-fidelity universal quantum gates. In this work, we design and demonstrate a complete high-fidelity gate set for the two-qubit system formed by the electron and nuclear spin of a nitrogen-vacancy center in diamond. We use gate set tomography (GST) to systematically optimize the gates and demonstrate single-qubit gate fidelities of up to <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <a:mn>99.999</a:mn> <a:mo stretchy="false">(</a:mo> <a:mn>1</a:mn> <a:mo stretchy="false">)</a:mo> <a:mi mathvariant="normal">%</a:mi> </a:math> and a two-qubit gate fidelity of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <g:mn>99.93</g:mn> <g:mo stretchy="false">(</g:mo> <g:mn>5</g:mn> <g:mo stretchy="false">)</g:mo> <g:mi mathvariant="normal">%</g:mi> </g:math> . Our gates are designed to decouple unwanted interactions and can be extended to other electron-nuclear spin systems. The high fidelities demonstrated provide opportunities towards larger-scale quantum processing with color-center qubits.