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Spin-swap gate in the presence of qubit inhomogeneity in a double quantum dot

2003; American Physical Society; Volume: 68; Issue: 5 Linguagem: Inglês

10.1103/physreva.68.052310

1538-4446

Xuedong Hu, S. Das Sarma,

Advancements in Semiconductor Devices and Circuit Design

We study theoretically the effects of qubit inhomogeneity on the quantum logic gate of qubit swap, which is an integral part of the operations of a quantum computer. Our focus here is to construct a robust pulse sequence for swap operation in the simultaneous presence of Zeeman inhomogeneity for quantum dot trapped electron spins and the finite-time ramp-up of exchange coupling in a double dot. We first present a geometric explanation of spin swap operation, mapping the two-qubit operation onto a single-qubit rotation. We then show that in this geometric picture a square-pulse sequence can be easily designed to perform swap in the presence of Zeeman inhomogeneity. Finally, we investigate how finite ramp-up times for the exchange coupling J negatively affect the performance of the swap gate sequence, and show how to correct the problems numerically.