Electron Sextets as Optically Addressable Molecular Qubits: Triplet Carbenes.

Area of Science:

• Quantum information science
• Materials science
• Organic chemistry

Background:

• Optically detected magnetic resonance (ODMR) is crucial for quantum information science and sensing.
• Current ODMR techniques often rely on diamond-NV centers or transition-metal complexes.
• Metal-free spin qubits offer cost-effectiveness and sustainability but face challenges with low ODMR signals in π-diradicals due to limited intersystem crossing (ISC).

Purpose of the Study:

• To explore electron sextets, specifically triplet carbenes, as a novel class of optically addressable spin qubits.
• To overcome the limitations of π-diradicals by engineering a ground singlet-triplet gap and facilitating singlet-to-triplet ISC.
• To unlock a new ODMR pathway with potential signal gains for improved quantum sensing and information processing.

Main Methods:

• Theoretical exploration of electron sextet systems, using triplet carbenes as a model.
• Molecular engineering strategies to widen the ground singlet-triplet gap beyond thermal energy.
• Leveraging vibronic effects to enable ground-state singlet-to-triplet intersystem crossing (ISC).
• Investigating carbene candidates incorporating stabilization strategies.

Main Results:

• Demonstrated that molecular engineering can widen the ground singlet-triplet gap in triplet carbenes.
• Showcased how vibronic effects can facilitate ground-state singlet-to-triplet ISC.
• Proposed a new ODMR pathway with potential signal gains by controlling ISC rates and spin selectivity.
• Identified three realistic carbene candidates for further development.

Conclusions:

• Electron sextets, particularly triplet carbenes, represent a promising avenue for developing advanced spin qubits.
• Engineered ISC pathways in these systems can significantly enhance ODMR signals.
• This research opens up a new realm of quantum materials for quantum information science and sensing applications.