Fig. 3
Performance of the graphene-based SWAP1/2 for different nanoribbon width W and Fermi energy EF. Here the separation between the nanoribbons is set to dz = 1 nm, and the in plane momentum along the ribbon to \(k_{|||}W = 0.4\). a Probability of still having one plasmon in each mode when one plasmon is input into each mode after the input plasmons evolve along the interaction length \(L_{{\mathrm{SWAP}}^{1/2}}\). We find a range (shown in white) where the success probability is over 80% for reasonable physical parameters. b Probability of finding two plasmons in one nanoribbon after the interaction between the initial plasmons occurs. This is the “failure probability” of the gate, as it corresponds to events which take us out of the logical qubit subspace. As expected, these data show that in the region where P|11〉 is maximized the failure probability is significantly suppressed. c Probability of losing both initial plasmons after they evolve along a distance \(L_{{\mathrm{SWAP}}^{1/2}}\). d Interaction length \(L_{{\mathrm{SWAP}}^{1/2}}\) required to perform the SWAP1/2 logic gate. For the plotted range, we find that, above EF = 0.1 eV, the required interaction length is always shorter than the plasmon decay length (which is ≈ 500 nm for a 500 fs lifetime). e Success probability of the |11〉 input state as a function of the plasmon lifetime 1/γ, maximized over the same W and EF range as in panels a–c
