Figure 1

Optically induced spin polarization generates states for quantum information applications near room temperature. (a) In magnetic resonance experiments, the Rabi frequency, \(\Omega\), can be comparable to the transition (Larmor) frequency, \(\omega\). In this strong field limit, it is possible to completely manipulate a quantum state (qubit). However, the energy gap between states is small relative to \(k_BT\). This is a source of uncertainty when the state is initialized. (b) In optical transitions, the energy gap is large relative to \(k_BT\). But the Rabi frequency is much less than the transition frequency, which means that gate operations done with weak optical fields will be incomplete and noisy. (c) By coupling optical excitations to an internal conversion process, such as singlet fission (wavy arrow), one may capitalize on the advantages of both methods, provided that the relaxation is state-selective.