Optically Detected Magnetic Resonance on Carbene Molecular Qubits
Simon Roggors, Nico Striegler, Thomas Unden, Oleksiy V. Khavryuchenko, Alon Salhov, Jochen Scharpf, Martin B. Plenio, Alex Retzker, Fedor Jelezko, Matthias Pfender, Philipp Neumann, Tim R. Eichhorn, Tobias A. Schaub, Ilai Schwartz
Abstract
Solid-state quantum systems with optical and spin degrees of freedom have found widespread application in emerging quantum technologies. Recently, molecular qubits came forward as precisely tunable entities that present a compelling alternative to well-established yet hard-to-tune point defects in solid-state systems. In this work, we disclose ground-state triplet carbenes as purely organic qubits comprising two unpaired electrons in close proximity that can be generated in a crystalline matrix with high spatial accuracy via in situ photoactivation. We further demonstrate how state-of-the-art multireference quantum chemical calculations provide insight into their fundamental spin characteristics. As a result, several key assets were realized in a single solid-state qubit material under cryogenic conditions: The exclusive use of light elements (C, H, N, O), photolithographic patterning, optical spin-selective transitions, and a large zero-field splitting in the GHz regime, which, taken together, lays the ground for optically detected magnetic resonance with remarkable fluorescence contrast of >40% and record-high spin coherence times of T 2 = 157(4) μs at 5 K.