Physics Colloquium: Molecular Quantum Spin Science

Prof. Stephen Hill, Florida State University

Abstract: Electron and nuclear spins in molecules possess discrete quantum states that can be chemically tuned and coherently manipulated by means of external electromagnetic fields [1]. Magnetic molecules therefore provide a versatile and relatively simple platform for storing and processing quantum information. However, performance of useful quantum tasks requires significant numbers of quantum bits (qubits) with long coherence, and a reliable manner with which to integrate them into devices for implementation of quantum logic operations. This ‘scalability’ is arguably one of the challenges for which a bottom-up synthetic approach is best-suited. Molecules, being more versatile than isolated atoms or ions, and yet microscopic, are the quantum objects with the highest capacity to form ordered states at the nanoscale using chemical tools. After a general introduction, I will highlight work performed in my group at the Florida State University, with emphasis on the spin-orbital moments associated with lanthanide ions, whereby synthetic tuning of their molecular environment can give rise to so-called clock transitions (CTs) – avoided Zeeman level crossings that provide optimal operating points at which the electron spin dynamics decouple from the surrounding nuclear bath, leading to enhanced coherence [2]. Results of pulsed electron spin resonance measurements [2-4] and quantum dynamics simulations [5] will be presented for several contrasting molecular spin systems, illustrating the versatility of the molecular approach to quantum spin science.

[1] A. Gaita‐Ariño, F. Luis, S. Hill, E. Coronado, Nat. Chem. 11, 301 – 309 (2019).
[2] M. Shiddiq et al., Nature 531, 348 – 351 (2016).
[3] K. Kundu et al. Nat. Chem. 14, 392 – 397 (2021).
[4] P. W. Smith et al., J. Am. Chem. Soc. 146, 5781 – 5785 (2024).
[5] K. Kundu et al., Comms. Phys. 6, 38 (2023).