Issue 23, 2022

Chemical control of spin–lattice relaxation to discover a room temperature molecular qubit

Abstract

The second quantum revolution harnesses exquisite quantum control for a slate of diverse applications including sensing, communication, and computation. Of the many candidates for building quantum systems, molecules offer both tunability and specificity, but the principles to enable high temperature operation are not well established. Spin–lattice relaxation, represented by the time constant T1, is the primary factor dictating the high temperature performance of quantum bits (qubits), and serves as the upper limit on qubit coherence times (T2). For molecular qubits at elevated temperatures (>100 K), molecular vibrations facilitate rapid spin–lattice relaxation which limits T2 to well below operational minimums for certain quantum technologies. Here we identify the effects of controlling orbital angular momentum through metal coordination geometry and ligand rigidity via π-conjugation on T1 relaxation in three four-coordinate Cu2+S = ½ qubit candidates: bis(N,N′-dimethyl-4-amino-3-penten-2-imine) copper(II) (Me2Nac)2 (1), bis(acetylacetone)ethylenediamine copper(II) Cu(acacen) (2), and tetramethyltetraazaannulene copper(II) Cu(tmtaa) (3). We obtain significant T1 improvement upon changing from tetrahedral to square planar geometries through changes in orbital angular momentum. T1 is further improved with greater π-conjugation in the ligand framework. Our electronic structure calculations reveal that the reduced motion of low energy vibrations in the primary coordination sphere slows relaxation and increases T1. These principles enable us to report a new molecular qubit candidate with room temperature T2 = 0.43 μs, and establishes guidelines for designing novel qubit candidates operating above 100 K.

Graphical abstract: Chemical control of spin–lattice relaxation to discover a room temperature molecular qubit

Supplementary files

Article information

Article type
Edge Article
Submitted
04 nov. 2021
Accepted
16 mai 2022
First published
17 mai 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2022,13, 7034-7045

Chemical control of spin–lattice relaxation to discover a room temperature molecular qubit

M. J. Amdur, K. R. Mullin, M. J. Waters, D. Puggioni, M. K. Wojnar, M. Gu, L. Sun, P. H. Oyala, J. M. Rondinelli and D. E. Freedman, Chem. Sci., 2022, 13, 7034 DOI: 10.1039/D1SC06130E

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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