Biomedical subjects

Xuedong Hu

Publications and source records attributed to Xuedong Hu.

4 recordsLinked to original sources

PubMed2006

Charge-fluctuation-induced dephasing of exchange-coupled spin qubits.

Exchange-coupled spin qubits in semiconductor nanostructures are shown to be vulnerable to dephasing caused by charge noise invariably present in the semiconductor environment. This decoherence of exchange gate by environmental charge fluctuations arises from the fundamental Coulombic nature of the Heisenberg coupling and presents a serious challenge to the scalability of the widely studied exchange gate solid state spin quantum computer architectures. We estimate dephasing times for coupled spin qubits in a wide range (from 1 ns up to >1 micros) depending on the exchange coupling strength and its sensitivity to charge fluctuations.

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PubMed2006

Quantum control of donor electrons at the Si-SiO2 interface.

Prospects for the quantum control of electrons in the silicon quantum computer architecture are considered theoretically. In particular, we investigate the feasibility of shuttling donor-bound electrons between the impurity in the bulk and the Si-SiO2 interface by tuning an external electric field. We calculate the shuttling time to range from subpicoseconds to nanoseconds depending on the distance (approximately 10-50 nm) of the donor from the interface. Our results establish that quantum control in such nanostructure architectures could, in principle, be achieved.

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PubMed2003

Disentangling the exchange coupling of entangled donors in the Si quantum computer architecture.

We develop a theory for micro-Raman scattering by single and coupled two-donor states in silicon. We find the Raman spectra to have significant dependence on the donor exchange splitting and the relative spatial positions of the two-donor sites. In particular, we establish a strong correlation between the temperature dependence of the Raman peak intensity and the interdonor exchange coupling. Micro-Raman scattering can therefore potentially become a powerful tool to measure interqubit coupling in the development of a Si quantum computer architecture.

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PubMed2001

Exchange in silicon-based quantum computer architecture.

The silicon-based quantum computer proposal has been one of the actively pursued ideas during the past three years. Here we calculate the donor electron exchange in silicon and germanium, and demonstrate an atomic-scale challenge for quantum computing in Si (and Ge), as the six (four) conduction-band minima in Si (Ge) lead to intervalley electronic interference, generating strong oscillations in the exchange splitting of two-donor two-electron states. Donor positioning with atomic-scale precision within the unit cell thus becomes a decisive factor in determining the strength of the exchange coupling-a fundamental ingredient for two-qubit operations in a silicon-based quantum computer.

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