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Oxide-Semiconductor Materials for Quantum Computation

Scalable fault-tolerant quantum computer architectures require quantum gates that operate within a small fraction of the qubit decoherence time and with high accuracy over a bandwidth set by the decoherence rate. Electron spin quantum bits in Si are promising because of long decoherence times (~0.5 ms), but electrical gating schemes still seem problematic. Oxide-semiconductor heterostructures have the potential for precise electrical control of gate operations in the semiconductor, using optical rectification in the ferroelectric oxide. Accurate (~80 dB), local (~10 nm), dynamic (>THz) and programmable optical control over electric polarization in the ferroelectric can be achieved using existing technology. Optical techniques may also be useful in rapid initialization of the quantum computer, and for providing a source of initialized qubits to use for quantum error correction. Advantages of optical methods will be discussed within a framework proposed for a quantum information processor using ferroelectrically coupled electron spins and Ge quantum dots in Si.