Two-qubit operation on Majorana qubits in ordinary-qubit chains
Yu. Makhlin+*, S. Backens×, A. Shnirman×°
+Condensed-matter physics Laboratory, National Research University Higher School of Economics, 101000 Moscow, Russia
*Landau Institute for Theoretical Physics, 142432 Chernogolovka, Russia
×Institut für Theorie der Kondensierten Materie, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
°Institute of Nanotechnology, Karlsruhe Institute of Technology, D-76344 Eggenstein-Leopoldshafen, Germany
Abstract
Majorana zero modes can be simulated in structures based on spin or
quasi-spin degrees
of freedom,
e.g., Josephson-qubit chains. Braiding of Majorana degrees of freedom is
realized using
T-junctions supplied with an auxiliary spin (ancilla). Motivated by
prospective experiments, we
analyze the braiding in the spin representation, which provides the basis
for the analysis of
imperfections characteristic to the spin and qubit designs. The result of
the braiding operation is
straightforwardly found for the initial basis states of the two qubits
and the ancilla, up to phase
factors. Here we fix these phase factors and thus describe the complete
two-qubit operation. This
result is relevant for physical simulation of the Majorana qubits in
Josephson-qubit chains and
other spin or qubit structures.