Decoherence of electron spin qubit during transfer between two semiconductor quantum dots at low magnetic fields

Building a scalable semiconductor-based quantum computer would greatly benefit from coherent spin transfer. The authors analyze here the decoherence of an electron spin qubit adiabatically transferred between two tunnel-coupled quantum dots in the presence of typical disorder and charge noise. They identify key error mechanisms: spin relaxation due to spin-orbit mixing and dephasing activated by differences in Zeeman splitting. These results suggest a minimum tunnel coupling required for coherent transfer across longer quantum dot arrays in Si and GaAs.