We present realistic simulation for single and double phosphorous donors in a silicon‐based quantum computer design by solving a valley‐orbit coupled effective‐mass equation for describing phosphorous donors in strained silicon quantum well (QW). Using a generalized unrestricted Hartree‐Fock method, we solve the two‐electron effective‐mass equation with quantum well confinement and realistic gate potentials. The effects of QW width, gate voltages, donor separation, and donor position shift on the lowest singlet and triplet energies and their charge distributions for a neighboring donor pair in the quantum computer(QC) architecture are analyzed. The gate tunability are defined and evaluated for a typical QC design. Estimates are obtained for the duration of spin half‐swap gate operation.We present realistic simulation for single and double phosphorous donors in a silicon‐based quantum computer design by solving a valley‐orbit coupled effective‐mass equation for describing phosphorous donors in strained silicon quantum well (QW). Using a generalized unrestricted Hartree‐Fock method, we solve the two‐electron effective‐mass equation with quantum well confinement and realistic gate potentials. The effects of QW width, gate voltages, donor separation, and donor position shift on the lowest singlet and triplet energies and their charge distributions for a neighboring donor pair in the quantum computer(QC) architecture are analyzed. The gate tunability are defined and evaluated for a typical QC design. Estimates are obtained for the duration of spin half‐swap gate operation.

AIP conference proceedingsJan 1, 20080 citations

Charge qubits in semiconductor quantum computer architecture: Tunnel coupling and decoherence

Xuedong Hu, Belita Koiller, S. Das Sarma

We consider charge qubits based on shallow donor electron states in silicon and coupled quantum dots in GaAs. Specifically, we study the feasibility of ${P}_{2}^{+}$ charge qubits in Si, focusing on single qubit properties in terms of tunnel coupling between the two phosphorus donors and qubit decoherence caused by electron-phonon interaction. By taking into consideration the multivalley structure of the Si conduction band, we show that intervalley quantum interference has important consequences for single-qubit operations of ${P}_{2}^{+}$ charge qubits. In particular, the valley interference leads to a tunnel-coupling strength distribution centered around zero. On the other hand, we find that the Si band structure does not dramatically affect the electron-phonon coupling and consequently, qubit coherence. We also critically compare charge qubit properties for $\mathrm{Si}:{P}_{2}^{+}$ and GaAs double quantum dot quantum computer architectures.We consider charge qubits based on shallow donor electron states in silicon and coupled quantum dots in GaAs. Specifically, we study the feasibility of ${P}_{2}^{+}$ charge qubits in Si, focusing on single qubit properties in terms of tunnel coupling between the two phosphorus donors and qubit decoherence caused by electron-phonon interaction. By taking into consideration the multivalley structure of the Si conduction band, we show that intervalley quantum interference has important consequences for single-qubit operations of ${P}_{2}^{+}$ charge qubits. In particular, the valley interference leads to a tunnel-coupling strength distribution centered around zero. On the other hand, we find that the Si band structure does not dramatically affect the electron-phonon coupling and consequently, qubit coherence. We also critically compare charge qubit properties for $\mathrm{Si}:{P}_{2}^{+}$ and GaAs double quantum dot quantum computer architectures.

arXiv:cond-mat/0412340Physical Review BJun 30, 200559 citations

Silicon Quantum Computers

Jun Yoneda

The Journal of The Institute of Image Information and Television EngineersJan 1, 20220 citations

We consider charge qubits based on shallow donor electron states in silicon and coupled quantum dots in GaAs. Specifically, we study the feasibility of

{P}_{2}^{+}

charge qubits in Si, focusing on single qubit properties in terms of tunnel coupling between the two phosphorus donors and qubit decoherence caused by electron-phonon interaction. By taking into consideration the multivalley structure of the Si conduction band, we show that intervalley quantum interference has important consequences for single-qubit operations of

{P}_{2}^{+}

charge qubits. In particular, the valley interference leads to a tunnel-coupling strength distribution centered around zero. On the other hand, we find that the Si band structure does not dramatically affect the electron-phonon coupling and consequently, qubit coherence. We also critically compare charge qubit properties for

\mathrm{Si}:{P}_{2}^{+}

and GaAs double quantum dot quantum computer architectures.