Spectrally-Addressable Multiqubit Molecules

Stephen von Kugelgen

The atomic precision enabled by bottom-up chemical synthesis offers pathway to create molecular qubits with tailored properties. Spin-bearing molecules are portable, can (self) assemble into arrays, and are readily tuned for integration into myriad potential architectures. By exploiting this modular strategy, we can advance from isolated qubits to systems featuring many interacting qubits. As we look to design more complex systems, a key relationship to understand is how the nanoscale spatial arrangement of two qubits dictates their coherence properties. To address this question, we developed a series of molecules featuring spectrally-distinct transition metal complexes hosting an early transition metal, Ti3+, and a late transition metal, Cu2+. By embedding them in a modular, rigid ligand framework we enforced specific through-space and through-bond interactions between qubits at increasing qubit-qubit distances. The spectral separation and our ability to prepare and study their monometallic analogues enabled us to disentangle different contributions to qubit decoherence. Across distances from 1.2 to 2.5 nm, we find that the presence of a second qubit with a different resonance frequency has a negligible effect on coherence, which is limited instead by ligand nuclear spins.

Funding Sources: U.S. Department of Energy, Office of Science, Basic Energy Sciences, award DE-SC0019356|the Arnold and Mabel Beckman Foundation through a Postdoctoral Fellowship in the Chemical Sciences