Molecular qubits based on potentially nuclear-spin-free nickel ions

Abstract

Molecular qubits with the longest coherence times thus far are based on nuclear-spin-carrying central ions. These nuclear spins can cause quantum state leakage, which is detrimental to quantum algorithm performance. We present two novel molecular qubits based on potentially nuclear spin-free Ni in the formal oxidation state 3+. (d₂₀-PPh₄)[Ni(mnt)₂] (Ni-mnt, mnt²⁻ = maleonitrile-1,2-dithiolate) possesses a coherence time of up to 38.7 μs at 7 K. Functionalization of the dithiolate ligand decreases the coherence time by a factor of only four in (HNEt₃)[Ni(dip)₂] (Ni-dip, dip²⁻ = 3-(diphenylphosphoryl)-methylbenzene-1,2-dithiolate), indicating that monoanionic Ni-dithiolene complexes are promising and robust building blocks for polynuclear molecular qubit gates.