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

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.

10 pages, 3 figures

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• Manipulation of a single charge in a double quantum dot
• Decoherence Rate of Semiconductor Charge Qubit Coupled to Acoustic Phonon Reservoir
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