Spin-Phonon Relaxation and Decoherence in a Three-Dimensional Paired-Ion Framework Composed of Vanadyl Porphyrin Qubits.

Abstract

Molecular electron spin qubits are an emerging platform for quantum technologies due to their atomic-scale synthetic tunability. Supramolecular structures can also place these qubits at precise positions within ordered arrays, allowing the scale-up of qubit architectures through a bottom-up approach. Here, we introduce the first three-dimensional paired-ion framework (PIF), VO-3D-PIF-1, which is composed of a concentrated array of S = 1/2 vanadyl porphyrin spin qubits arranged by ionic lattice interactions. The PIF was characterized using electron paramagnetic resonance spectroscopy to demonstrate the impact of framework structure and spin density on spin-lattice relaxation (T1) and spin decoherence (Tm). The high vanadyl porphyrin spin density within the framework (0.125 spins/nm3) promotes dipolar-driven decoherence, with Tm = 200-400 ns over a temperature range of 140-5 K. Spin-lattice relaxation mirrors that of vanadyl porphyrins in dilute solution, suggesting that the weak ionic interactions assembling the porphyrins within the secondary coordination sphere do not adversely affect phonon-induced T1 relaxation.