Quantum computer on InAs/GaSb heterostructures

The InAs/AlGaSb heterostructures are promising candidates for fabricating the quantum computer due to the large electron g-factor in the bulk InAs and hence large spin splitting of electronlike Landau levels in a quantizing magnetic field. The two lowest electronlike spin split levels can be used as a qubit of a quantum computer. Then the one-qubit operations can be performed by the circularly polarized light of photon energy approximately equal to the spin splitting of levels. These transitions are possible because of the mixing of the states of different spin orientations caused by the spin-orbit interaction. Previously it has been found that the additional AlGaSb layer can essentially enhance the spin splitting of electronlike levels when the magnetic field is normal to the InAs/AlGaSb interface due to the hybridization of electron and hole levels. Here we investigate the Landau-level structures in strained InAs/GaSb heterostructures using the scattering matrix method and Burt's envelope function theory. We obtain somewhat different results. The spin splitting of electronlike Landau levels considerably enlarges when the hybridization of electron and hole levels becomes negligibly small with the magnetic field increasing. We find that this splitting depends essentially on the lattice-mismatched strain and can be as large as 15 meV at magnetic field B ≥ 15 T for the structure grown on InAs.