All-spin-based ultrafast nano-logic elements with a Ni₄ cluster

Using high-level ab initio equation-of-motion coupled-cluster calculations, we present two new elementary laser-induced spin manipulation processes on Ni₄, namely spin bifurcation and spin merging, in which the spin density gets transferred from one to two magnetic centers, and vice versa. With these functional intramolecular processes at hand we are able to construct an all-spin-based OR gate, which, contrary to previously suggested nanologic elements [1], does not need any information carriers except the spins. The necessary spin-density localization is guaranteed by the non-perfect geometry of the cluster [2]. The spin-transfer scenarios allow us to also build a cyclic spin-SHIFT register.

We also exploit the Ni₄ cluster to derive two quantum-information operations, not possible classically. The one is the which-path information effect, in which the phase of the final spin state after two consecutive laser-induced transfers can reveal the exact path travelled by the spin density [3], and the other the universal pure-quantum SQUARE-ROOT-OF-NOT gate.

[1] W. Hübner, S. Kersten, and G. Lefkidis, Phys. Rev. B 79, 184431 (2009)
[2] D. Chaudhuri, H. P. Xiang, G. Lefkidis, and W. Hübner, Phys. Rev. B 90, 245113 (2014)
[3] D. Chaudhuri, G. Lefkidis, and W. Hübner, Phys. Rev. B (accepted)