Creating nuclear spin entanglement using an optical degree of freedom

Abstract

Molecular nanostructures are promising building blocks for future quantum technologies, provided methods of harnessing their multiple degrees of freedom can be identified and implemented. Due to low decoherence rates, nuclear spins are considered ideal candidates for storing quantum information, while optical excitations can give rise to fast and controllable interactions for information processing. A recent paper [M. Schaffry et al., Phys. Rev. Lett. 104, 200501 (2010)] proposed a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin. Building on the same idea, we present here an extended and much more detailed theoretical framework, showing that this method is in fact applicable to a much wider class of molecular structures than previously discussed in the original proposal.

Controlling and exploiting phases in multi-spin systems using electron spin resonance and nuclear magnetic resonance

“…much faster to apply a controlled phase gate, rather than, say, CNOT. A suitably selective dynamic phase gate on the electron spin applies an indirect CPHASE between nuclear spins and provides a very fast entangling operation between nuclear spins [30][31][32].…”

Coherent Storage of Photoexcited Triplet States UsingSi29Nuclear Spins in Silicon

“…The use of an optically driven mediator spin has been suggested as a way to control coupling between donor electron spins in silicon: the donor spins exhibit weak direct coupling, but mutually couple through the optically excited state of the mediator [8]. Such ideas could similarly be applied to couple nuclear spins, and, if the mediator spin is a photo-excited triplet with a spinzero single ground state, it would have the added advantage that it avoids long-term impact on the nuclear spin coherence [9][10][11].Photoexcited triplets are optically-generated electron spins (S = 1) which often exhibit large (positive or negative) spin polarization, thanks to preferential population of each of the triplet sub-levels following intersystem crossing and/or the differing decay rates of these sublevels to the ground singlet state [12,13]. Nuclear spins, in contrast, have weak thermal spin polarization at experimentally accessible conditions, due to its small magnetic moment.…”

“…The use of an optically driven mediator spin has been suggested as a way to control coupling between donor electron spins in silicon: the donor spins exhibit weak direct coupling, but mutually couple through the optically excited state of the mediator [8]. Such ideas could similarly be applied to couple nuclear spins, and, if the mediator spin is a photo-excited triplet with a spinzero single ground state, it would have the added advantage that it avoids long-term impact on the nuclear spin coherence [9][10][11].…”