High-Fidelity Electron Spin Gates for Scaling Diamond Quantum Registers
Timo Joas, Florian Ferlemann, Roberto Sailer, Philipp J. Vetter, Jingfu Zhang, Ressa S. Said, Tokuyuki Teraji, Shinobu Onoda, Tommaso Calarco, Genko T. Genov, Matthias M. Müller, Fedor Jelezko
Abstract
Diamond is a promising platform for quantum information processing as it can host highly coherent qubits that could allow for the construction of large quantum registers. A prerequisite for such devices is a coherent interaction between nitrogen-vacancy (NV) electron spins enabling scalable entanglement. Entanglement between dipolar-coupled NV spin pairs has been demonstrated but with a limited fidelity, and its error sources have not been characterized. Here, we design and implement a robust two-qubit gate between NV electron spins in diamond and quantify the influence of multiple error sources on the gate performance. Experimentally, we demonstrate a record gate fidelity of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msub> <a:mrow> <a:mi>F</a:mi> </a:mrow> <a:mrow> <a:mn>2</a:mn> <a:mi mathvariant="normal">q</a:mi> </a:mrow> </a:msub> <a:mo>=</a:mo> <a:mo stretchy="false">(</a:mo> <a:mn>96.0</a:mn> <a:mo>±</a:mo> <a:mn>2.5</a:mn> <a:mo stretchy="false">)</a:mo> <a:mi>%</a:mi> </a:mrow> </a:math> under ambient conditions. Our identification of the dominant errors paves the way towards NV-NV gates beyond the error correction threshold.