“Tailoring spin-spin interactions for emergent spin-spin properties"

Quantum Information and sensing are scientific topics of active interest from an industrial and
academic point of view(1, 2). The field’s relative nascency provides an excellent platform to explore a plethora of
solutions to improve encoding and read-out of information which are arbitrary spin states generated via electric or
magnetic fields resonant with spin→spin transitions. In this talk I will explore 2 different approaches, close to

publication, that I have been working on, in the Richard H. Friend group at Cambridge: (a) To use a proxy to spin-
orbit coupling by harnessing chirality which is a orthogonal dimension of physical manipulation and (b) by

attaching 2 open shell semiconductors in various geometries to provide a manifold for competition between
dipolar and exchange interactions. In method (a) I show how the information is transmitted and stored using the
angular momentum quantum number which couples with out-coupled photons and in method (b) I show how the
enhancement in excited state exchange interaction by orders of magnitude allows us to generate arbitrary
correlated spin states using relatively small magnetic fields and also allows us to use photons to encode spin
information for 200x longer than optical lifetimes at room temperature, enabling ground state spin polarisation for
qubit applications like NV- centers(3). This has thus far only been shown for much shorter lifetimes and in the
excited state (4, 5). All the materials I will talk about are purely organic and we have shown recently our prowess
in accessing the synthetic chemical space of all of these materials (6).
1.J. R. Weber, W. F. Koehl, J. B. Varley, A. Janotti, B. B. Buckley, C. G. Van de Walle, D. D. Awschalom,
Quantum computing with defects. Proceedings of the National Academy of Sciences 107, 8513–8518 (2010)
2. G. Popkin, Quest for qubits. Science (1979) 354, 1090–1093 (2016).
3. F. Jelezko, T. Gaebel, I. Popa, A. Gruber, J. Wrachtrup, Observation of Coherent Oscillations in a Single
Electron Spin. Phys Rev Lett 92, 076401 (2004).
4. M. Mayländer, S. Chen, E. R. Lorenzo, M. R. Wasielewski, S. Richert, Exploring Photogenerated Molecular
Quartet States as Spin Qubits and Qudits. J Am Chem Soc 143, 7050–7058 (2021).
5. M. Mayländer, P. Thielert, T. Quintes, A. Vargas Jentzsch, S. Richert, Room Temperature Electron Spin
Coherence in Photogenerated Molecular Spin Qubit Candidates. J Am Chem Soc 145, 14064–14069 (2023).
6. P. Murto, R. Chowdhury, S. Gorgon, E. Guo, W. Zeng, B. Li, Y. Sun, H. Francis, R. H. Friend, H. Bronstein,
Mesitylated trityl radicals, a platform for doublet emission: symmetry breaking, charge-transfer states and
conjugated polymers Nat Commun 14,4147 (2023)