Introduction
Researchers from Kumamoto University, in collaboration with institutions in South Korea and Taiwan, have identified a cobalt-based molecule featuring metal-metal bonds that can operate as a spin quantum bit (qubit). This discovery establishes a new method for designing molecular materials for quantum information technologies. The findings were published in Chemical Communications.
Background on Spin Qubits
Quantum computers utilize qubits, which can exist in multiple states simultaneously. Spin qubits, based on electron spin, are a type of qubit that can be controlled using magnetic resonance techniques. A challenge in this field involves creating stable molecular-level spin qubits with extended lifetimes.
The Cobalt Molecule
The research focused on a molecule named Co₃(dpa)₄Cl₂, which consists of three cobalt ions connected by direct metal-metal bonds. This compound is also a spin-crossover material, meaning its spin state can change under varying external conditions, such as temperature. Prior to this study, its capability to function as a spin qubit had not been experimentally verified.
Experimental Findings
Using magnetic measurements and pulsed electron paramagnetic resonance (EPR) spectroscopy, the team assessed the duration for which the electron spins within the molecule could maintain their quantum state. They observed slow magnetic relaxation and spin lifetimes that meet criteria for quantum information processing. The electron spin was found to be delocalized across all three cobalt ions, contributing to the stabilization of the quantum state.
The study also documented Rabi oscillations, indicating that the spin states can be coherently manipulated. These observations confirm that a molecule with metal-metal bonds can serve as a functional spin qubit.
Implications
Professor Shinya Hayami of Kumamoto University stated that this work provides a new approach for molecular qubit design, suggesting that rigid, multinuclear metal complexes can help suppress vibrations and extend spin lifetimes. The research is anticipated to contribute to the development of molecular-based quantum materials for applications in quantum computing, quantum memory, and spin-based electronics.