Long-Lived Electronic Spin Qubits in Single-Walled Carbon Nanotubes

Electron spins in solid-state systems offer the promise of spin-based information processing devices for quantum communication and computing. The key to preserving the encoding information is realized by the robust coherent spin state which acts against decoherence from losing the phase information. Single-walled carbon nanotubes (SWCNTs), an all-carbon one-dimensional material whose spin-free environment and weak spin-orbit coupling promise long spin coherence times, offer diverse freedom for extended functionality not available to bulk systems. Here, we report the creation of highly confined electron spins in SWCNTs by chemical functionalization through a bottom-up approach. The record long coherence time of 8.2 µs and spin-lattice relaxation time of 13 ms of these electronic spin qubits allow demonstration of quantum control operation manifested as Rabi oscillation. Investigation of the decoherence mechanism reveals an intrinsic coherence time of tens of milliseconds. These findings show that combining molecular approaches with one-dimensional crystalline systems provides a powerful route for reproducible and scalable quantum materials suitable for qubit applications.