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

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 multi-valley structure of the Si conduction band, we show that inter-valley 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 bandstructure does not dramatically affect the electron-phonon coupling and consequently, qubit coherence. We also critically compare charge qubit properties for Si:P$_2^+$ and GaAs double quantum dot quantum computer architectures.

[1]  M Y Simmons,et al.  Atomically precise placement of single dopants in si. , 2003, Physical review letters.

[2]  G. Guo,et al.  Reducing decoherence in quantum-computer memory with all quantum bits coupling to the same environment , 1996, quant-ph/9612003.

[3]  S. Das Sarma,et al.  Overview of spin‐based quantum dot quantum computation , 2002, cond-mat/0211358.

[4]  Xuedong Hu,et al.  Silicon-based spin and charge quantum computation , 2005 .

[5]  Electron exchange coupling for single-donor solid-state spin qubits , 2003, cond-mat/0309417.

[6]  Joel N. Schulman,et al.  Wave Mechanics Applied to Semiconductor Heterostructures , 1991 .

[7]  A. G. Fowler,et al.  Single-spin readout for buried dopant semiconductor qubits , 2004, quant-ph/0402077.

[8]  Xuedong Hu,et al.  Spin quantum computation in silicon nanostructures , 2005 .

[9]  Y. Makhlin,et al.  Quantum-state engineering with Josephson-junction devices , 2000, cond-mat/0011269.

[10]  Eli Yablonovitch,et al.  Electron-spin-resonance transistors for quantum computing in silicon-germanium heterostructures , 1999, quant-ph/9905096.

[11]  L. Vandersypen,et al.  Single-shot read-out of an individual electron spin in a quantum dot , 2004, Nature.

[12]  C. R. Stanley,et al.  Coherent manipulation of semiconductor quantum bits with terahertz radiation , 2001, Nature.

[13]  Xuedong Hu,et al.  Strain effects on silicon donor exchange: Quantum computer architecture considerations , 2002 .

[14]  Barenco,et al.  Conditional Quantum Dynamics and Logic Gates. , 1995, Physical review letters.

[15]  K. Andres,et al.  Low-temperature magnetic susceptibility of Si: P in the nonmetallic region , 1981 .

[16]  Leonid Fedichkin,et al.  A silicon-based nuclear magnetic resonance (NMR) quantum computer using resonant transfer of a single electron for the inter-qubit interaction , 2001 .

[17]  B. E. Kane,et al.  Hydrogenic spin quantum computing in silicon: a digital approach. , 2002, Physical review letters.

[18]  B. E. Kane.  Silicon‐Based Quantum Computation , 2000, quant-ph/0003031.

[19]  D. DiVincenzo,et al.  Quantum computation with quantum dots , 1997, cond-mat/9701055.

[20]  B. Chui,et al.  Single spin detection by magnetic resonance force microscopy , 2004, Nature.

[21]  G. J. Milburn,et al.  Charge-based quantum computing using single donors in semiconductors , 2004 .

[22]  L. Fedichkin,et al.  Error rate of a charge qubit coupled to an acoustic phonon reservoir (4 pages) , 2004 .

[23]  R. Jozsa,et al.  Quantum Computation and Shor's Factoring Algorithm , 1996 .

[24]  G. J. Milburn,et al.  Measuring the decoherence rate in a semiconductor charge qubit , 2003 .

[25]  D. D. Awschalom,et al.  Quantum information processing using quantum dot spins and cavity QED , 1999 .

[26]  B. E. Kane.  Can We Build a Large-Scale Quantum Computer Using Semiconductor Materials? , 2005 .

[27]  Matthieu Verstraete,et al.  First-principles computation of material properties: the ABINIT software project , 2002 .

[28]  I. Chuang,et al.  Quantum Computation and Quantum Information: Bibliography , 2010 .

[29]  A. Gossard,et al.  Manipulation of a single charge in a double quantum dot. , 2004, Physical review letters.

[30]  Y. Tokura,et al.  Dephasing due to background charge fluctuations , 2003, cond-mat/0303412.

[31]  H. Cheong,et al.  Coherent manipulation of electronic States in a double quantum dot. , 2003, Physical review letters.

[32]  A. Baldereschi.  Valley-Orbit Interaction in Semiconductors , 1970 .

[33]  G. Mahan.  Many-particle physics , 1981 .

[34]  Xuedong Hu,et al.  Hilbert-space structure of a solid-state quantum computer: Two-electron states of a double-quantum-dot artificial molecule , 2000 .

[35]  Xuedong Hu,et al.  Exchange in silicon-based quantum computer architecture. , 2002, Physical review letters.

[36]  T Yamamoto,et al.  Charge echo in a cooper-pair box. , 2002, Physical review letters.

[37]  Y. Pashkin,et al.  Coherent control of macroscopic quantum states in a single-Cooper-pair box , 1999, Nature.

[38]  K. A. Valiev,et al.  Coherent charge qubits based on GaAs quantum dots with a built-in barrier , 2000 .

[39]  B. E. Kane.  A silicon-based nuclear spin quantum computer , 1998, Nature.