Research

Coordination complexes for quantum computation

Quantum computers offer tremendous promise because of the low barrier to implementation; a system with only 1,000 qubits could both break modern encryption schemes and accurately model quantum systems. The greatest challenge to quantum computing is creating “qubits,” the basic informational units of quantum computers, which can support long-lived superposition states. We are examining the implementation of electron spins in paramagnetic coordination complexes for this purpose. Electron spins in coordination complexes are good qubit candidates due to their reproducibility and potential for scalability. However, the phenomena that cause decoherence, or the collapse of electronic spin superposition states, are not understood well enough to permit the rational design of complexes that can effectively host qubits. Our efforts to prepare qubits for electron spin based quantum computation entail in-depth investigations of the coherent spin dynamics of transition metal complexes with an eye toward understanding and eliminating common sources of decoherence. As such, much of our current efforts are focused on the preparation of paramagnetic species comprised of elements for which greater than 90% of the natural abundance corresponds to isotopes that have no nuclear spin.


Publications

Forging Solid-State Qubit Design Principles in a Molecular Furnace
Graham, M. J.; Zadrozny, J. M.; Fataftah, M. S.; Freedman, D. E. Chem. Mater. 2017, 29, 1885–1897.

Synthetic Approach to Determine the Effect of Nuclear Spin Distance on Electronic Spin Decoherence
Graham, M. J.; Yu, C.; Krzyaniak, M.; Wasielewski, M.; Freedman, D. E. J. Am. Chem. Soc. 2017, 139, 3196–3201.

Long Coherence Times in Nuclear Spin-Free Vanadyl Qubits
Yu, C.; Graham, M. J.; Zadrozny, J. M.; Niklas, J.; Krzyaniak, M.; Wasielewski, M. R.; Poluektov O. G.; Freedman, D. E. J. Am. Chem. Soc. 2016, 138, 14678–14685.

Unexpected Suppression of Spin-Lattice Relaxation via High Magnetic Field in a High-Spin Iron(III) Complex
Zadrozny, J. M.; Graham, M. J.; Krzyaniak, M. D.; Wasielewski, M. R.; Freedman, D. E. Chem. Commun. 2016, 52, 10175–10178.

Employing Forbidden Transitions as Qubits in a Nuclear Spin-Free Chromium Complex
Fataftah, M. S.; Zadrozny, J. M.; Coste, S. C.; Graham, M. J.; Rogers, D. M.; Freedman, D. E. J. Am. Chem. Soc. 2016, 138, 1344–1348.

Qubit Control Limited by Spin–Lattice Relaxation in a Nuclear Spin–Free Iron(III) Complex
Zadrozny, J. M.; Freedman, D. E. Inorg. Chem. 2015, 54, 12027–12031.

Millisecond Coherence Time in a Tunable Molecular Electronic Spin Qubit
Zadrozny, J. M.; Niklas, J.; Poluektov, O. G.; Freedman, D. E. ACS Central Science 2015, 1, 488–492.

Multiple Quantum Coherences from Hyperfine Transitions in a Vanadium(IV) Complex
Zadrozny, J. M.; Niklas, J.; Poluektov, O. G.; Freedman, D. E. J. Am. Chem. Soc. 2014, 136, 15841–15844.

Influence of Electronic Spin and Spin-Orbit Coupling on Decoherence in Mononuclear Transition Metal Complexes
Graham, M. J.; Zadrozny, J. M.; Shiddiq, M.; Anderson, J. S.; Fataftah, M. S.; Hill, S.; Freedman, D. E. J. Am. Chem. Soc. 2014, 136, 7623–7626.

Harvesting magnetic anisotropy from diamagnetic elements for the synthesis of a new class of permanent magnets

With the decreasing supply of rare earth metals and the increasing incorporation of strong magnets into renewable energy technologies, the DOE has made replacing rare earth magnets a priority. Replacing rare earths requires introducing a new source of anisotropy—or preferred orientation—into magnets. In conjunction with the solid-state magnet synthesis, we will synthesize nanoparticles and molecular models to understand how anisotropy is imparted from diamagnetic heavy elements. The new magnets synthesized by this approach will incorporate earth abundant metals, rather than the rare earth metals currently used. This will greatly reduce the cost of renewable energy technologies that rely on the use of strong permanent magnets, such as wind turbines and electric cars.


Publications

Discovery of FeBi2
Walsh, J. P. S.; Clarke, S. M.; Meng, Y.; Jacobsen, S. D.; Freedman, D. E. ACS Cent. Sci. 2016, 2, 867–871.

Discovery of a Superconducting Cu–Bi Intermetallic Compound by High-pressure Synthesis
Clarke, S. M.; Walsh, J. P. S.; Amsler, M.; Malliakas, C. D.; Yu, T.; Goedecker, S.; Wang, Y.; Wolverton, C.; Freedman, D. E. Angew. Chem. Int. Ed. 2016, 55, 13446–13449.

Enhancement of Magnetic Anisotropy in a Mn–Bi Heterobimetallic Complex
Pearson, T. J.; Fataftah, M. S.  Freedman, D. E. Chem. Commun. 2016, 52, 11394–11397.

(BiSe)1.23CrSe2 and (BiSe)1.22(Cr1.2Se2)2: Magnetic Anisotropy in the First Structurally Characterized Bi-Se-Cr Ternary Compounds
Clarke, S. M.; Freedman, D. E. Inorg. Chem. 2015, 54, 2765–2771.

Accelerating Functional Materials Discovery
Rondinelli, J. R.; Benedek, N. A.; Freedman, D. E.; Kavner, A.; Rodriguez, E. E.; Toberer, E. S.; Martin, L. W. Am. Ceram. Soc. Bull. 2013, 92, 14.

New superconductors from transition metal analogues of heavy fermion superconductors

Heavy fermion superconductors are an extraordinary class of intermetallic superconductors with electrons that behave as if they are 1,000 times more massive than ordinary electrons. We will exploit a recent theoretical breakthrough to target new superconductors with higher critical temperatures. Our synthetic strategy will focus upon integrating transition metals with electrons that are partially delocalized to increase orbital overlap while maintaining the electronic structure necessary for heavy fermion superconductivity. New superconductors will be studied by magnetometry and Mössbauer spectroscopy in order to contextualize their properties within the framework of the nascent theory of heavy fermion superconductivity. This project will involve feedback between theory and experiment.