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Spin-valley lifetimes in a silicon quantum dot with tunable valley splitting
1Australian Research Council Centre of Excellence for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, The University of New South Wales, Sydney 2052, Australia.
Nature Communications
|June 28, 2013
Summary
We demonstrate tunable valley splitting in silicon quantum dots for spin qubits. This control enables precise manipulation and long spin lifetimes exceeding 2 seconds, crucial for quantum computing advancements.
Area of Science:
- Quantum Information Science
- Condensed Matter Physics
- Materials Science
Background:
- Silicon is a leading material for quantum computation due to its compatibility with existing semiconductor technology.
- The degeneracy of conduction band minima (valleys) in silicon must be overcome to create stable spin qubits.
- Achieving sufficient valley splitting is critical for forming well-defined and long-lived spin qubits.
Purpose of the Study:
- To demonstrate electrostatic gate control for tuning valley separation in silicon quantum dots.
- To investigate the impact of valley splitting on spin qubit properties, including relaxation times.
- To understand the mechanisms governing spin relaxation in silicon quantum dots.
Main Methods:
- Fabrication and characterization of metal-oxide-semiconductor quantum dots.
- Electrostatic gate control to tune the electric field and valley splitting.
- Single-shot spin readout techniques.
- Measurement of spin relaxation rates under varying magnetic fields and valley configurations.
Main Results:
- Valley separation was accurately tuned via electrostatic gates, achieving splittings from 0.3-0.8 meV.
- The valley splitting showed a linear dependence on the applied electric field, consistent with theoretical predictions.
- One-electron spin lifetimes exceeding 2 seconds were measured, indicating long coherence times.
- Spin relaxation was identified to occur via phonon emission due to spin-orbit coupling between valley states.
- A significant enhancement in relaxation rate (hot-spot) was observed when Zeeman and valley splittings coincided.
Conclusions:
- Electrostatic gate control provides a powerful method for tuning valley splitting in silicon quantum dots.
- The demonstrated control and long spin lifetimes are significant steps towards scalable silicon-based quantum computing.
- The identified spin relaxation mechanism via phonon emission offers new insights for optimizing qubit design and performance.
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