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Quantum Mechanics

Hole spin relaxation in Ge–Si core–shell nanowire qubits

Profile image of Charles MarcusCharles Marcus

2011, Nature Nanotechnology

https://doi.org/10.1038/NNANO.2011.234
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13 pages

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Abstract

Controlling decoherence is the most challenging task in realizing quantum information hardware 1-3 . Single electron spins in gallium arsenide are a leading candidate among solidstate implementations, however strong coupling to nuclear spins in the substrate hinders this approach 4-6 . To realize spin qubits in a nuclear-spin-free system, intensive studies based on group-IV semiconductor are being pursued. In this case, the challenge is primarily control of materials and interfaces, and device nanofabrication. We report important steps toward implementing spin qubits in a predominantly nuclear-spin-free system by demonstrating state preparation, pulsed gate control, and charge-sensing spin readout of confined hole spins in a one-dimensional Ge/Si nanowire. With fast gating, we measure T 1 spin relaxation times in coupled quantum dots approaching 1 ms, increasing with lower magnetic field, consistent with a spin-orbit mechanism that is usually masked by hyperfine contributions. Since Loss and DiVincenzo's proposal 1 , the promise of quantum dots for solid state quantum computation has been underscored by the successful initialization, manipulation and readout of electron spins in GaAs systems 5,7-9 . The electronic wave functions in these systems typically overlap with a large number of nuclear spins that are difficult to control and in most cases thermally randomized. The resulting intrinsic spin decoherence rates 4-6 have been successfully reduced by spin-echo techniques 6,10 but require complex gate sequences that complicate multiqubit operations 11 . The prospect of achieving long coherence times in group IV materials with

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