Semi-empirical Haken–Strobl model for molecular spin qubits

• Published in: New journal of physics Vol. 25; no. 9; pp. 93031 - 93040
• Main Authors: Aruachan, Katy, Colón, Yamil J, Aravena, Daniel, Herrera, Felipe
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.09.2023
• Subjects: Data processing; electron spin resonance; Electronic structure; Empirical equations; First principles; Haken–Strobl theory; Magnetic fields; molecular spin qubits; Physics; Quantum mechanics; Qubits (quantum computing); Redfield equation; spectral density; spin coherence; spin-lattice interaction; Temperature dependence; Tensors
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/acf2bd

Abstract Understanding the physical processes that determine the relaxation T 1 and dephasing T 2 times of molecular spin qubits is critical for envisioned applications in quantum metrology and information processing. Recent spin-echo measurements of solid-state molecular spin qubits have stimulated the development of quantum mechanical models for predicting intrinsic qubit timescales using first-principles electronic structure methods. We develop an alternative semi-empirical approach to construct Redfield quantum master equations for molecular spin qubits using a stochastic Haken–Strobl theory for a central spin with fluctuating gyromagnetic tensor due to spin-lattice interaction and fluctuating local magnetic field due to interactions with lattice spins. Using two vanadium-based spin qubits as case studies, we compute qubit population and decoherence times as a function of temperature and magnetic field, using a bath spectral density parametrized with a small number of T 1 measurements. The theory quantitatively agrees with experimental data over a range of conditions beyond those used to parameterize the model, demonstrating the generalization potential of the method. The ability of the model to describe the temperature dependence of the ratio T 2 / T 1 is discussed and possible applications for designing novel molecule-based quantum magnetometers are suggested.