Investigation of High-Symmetry Lanthanide Complexes as Molecular Electron Spin Qubits

Eduardo Hernandez Requejo,^a Ferdous Ara,^b Stephen Hill,^b Michael Shatruk^a

a Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306
b Department of Physics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310

A quantum bit (qubit) is the fundamental unit of quantum information processing that relies on a superposition of two quantum states, a|0⟩+ b|1⟩. Molecular electron spin qubits (MESQs) offer the advantage of high synthetic tunability but suffer from rapid decoherence, i.e., the loss of the superposition state. Clock transitions, which emerge as energy gaps due to avoided crossing of electronic states, decrease the qubit’s sensitivity to the surrounding magnetic noise, leading to higher coherence times.¹ Such transitions can be designed rationally by matching the rotational symmetry of lanthanide complexes to the |m_J| value of the ground state doublet generated by crystal-field splitting.² To that end, we have synthesized mono- and dinuclear complexes of lanthanide ions with integer-value total angular momenta (J). The high-symmetry square-antiprismatic coordination environment is achieved using tetradentate phthalocyanine ligands combined with bi- or tetradentate ancillary ligands. Initial EPR measurements confirm the presence of clock transitions. The synthesis of the dimers of clock-transition qubits opens a path to the physical realization of molecular two-qubit logic gates.

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