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

Xuedong Hu·Belita Koiller·S. Das Sarma
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Abstract

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.

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Xuedong Hu, Belita Koiller, S. Das Sarma. 2004-12-13. Charge qubits in semiconductor quantum computer architectures: Tunnel coupling and decoherence. https://doi.org/10.1103/physrevb.71.235332

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