Multiple
Quantum Coherences from Hyperfine Transitions
in a Vanadium(IV) Complex
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Abstract
We report a vanadium complex in a
nuclear-spin free ligand field
that displays two key properties for an ideal candidate qubit system:
long coherence times that persist at high temperature, <i>T</i><sub>2</sub> = 1.2 μs at 80 K, and the observation of quantum
coherences from multiple transitions. The electron paramagnetic resonance
(EPR) spectrum of the complex [V(C<sub>8</sub>S<sub>8</sub>)<sub>3</sub>]<sup>2–</sup> displays multiple transitions arising from
a manifold of states produced by the hyperfine coupling of the <i>S</i> = <sup>1</sup>/<sub>2</sub> electron spin and <i>I</i> = <sup>7</sup>/<sub>2</sub> nuclear spin. Transient nutation
experiments reveal Rabi oscillations for multiple transitions. These
observations suggest that each pair of hyperfine levels hosted within
[V(C<sub>8</sub>S<sub>8</sub>)<sub>3</sub>]<sup>2–</sup> are
candidate qubits. The realization of multiple quantum coherences within
a transition metal complex illustrates an emerging method of developing
scalability and addressability in electron spin qubits. This study
presents a rare molecular demonstration of multiple Rabi oscillations
originating from separate transitions. These results extend observations
of multiple quantum coherences from prior reports in solid-state compounds
to the new realm of highly modifiable coordination compounds