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Statistical characterization of valley coupling in Si/SiGe quantum dots via g-factor measurements near a valley vortex
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Statistical characterization of valley coupling in Si/SiGe quantum dots via g-factor measurements near a valley vortex
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The presence of low-energy valley excitations in Si/SiGe heterostructures often causes spin qubits to fail. It is therefore important to develop robust protocols for characterizing the valley coupling. Here, we show that realistically sized samplings of valley energy distributions tend to dramatically overestimate the average valley coupling. But we find that knowledge of the valley phase, in addition to the valley splitting, can significantly improve our estimates. Motivated by this understanding, we propose a novel method to probe the valley phase landscape across the quantum well using simple $g$-factor measurements. An important calibration step in this procedure is to measure $g$ in a loop enclosing a valley vortex, where the valley phase winds by $\pm 2\pi$ around a zero of the valley splitting. This proposal establishes an important new tool for probing spin qubits, and it can be implemented in current experiments.
Forward citations
Cited by 9 Pith papers
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Complete measurement of tunnel- and valley-coupling parameters in a silicon double quantum dot
High-resolution DAXS spectroscopy extracts all intravalley and intervalley tunnel couplings plus valley phases in a Si double quantum dot, showing phases set anticrossing gap ratios and evolve with gate-tuned dot position.
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Complete measurement of tunnel- and valley-coupling parameters in a silicon double quantum dot
Researchers extracted the full set of tunnel-coupling magnitudes and valley phases in a Si/SiGe double quantum dot by measuring all four anticrossing gaps and fitting a four-level model.
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Spin Qubit Leapfrogging: Dynamics of shuttling electrons on top of another
Mobile spin qubits in silicon can leapfrog over occupied dots by exploiting low valley splitting, enabling new connectivity routes and SWAP^γ entangling gates.
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Mapping g-factors and complex intervalley coupling in Si/SiGe by conveyor-mode shuttling
Entangled-pair conveyor shuttling yields a 2D g-factor map of Si/SiGe quantum dots with two anticorrelated valley components, enabling the first lateral reconstruction of the complex intervalley coupling.
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Confinement drives valley splitting above 4K in buried silicon quantum wells
Tight electrostatic confinement drives single-electron valley splitting above 4 K (up to 0.76 meV) in buried silicon quantum wells, with a linear coefficient ~0.22 versus orbital energy in three of four dots.
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High-fidelity EDSR in Si/SiGe Wiggle Wells
Alloy disorder in wiggle wells both randomizes and enables EDSR, with sweet spots permitting high-fidelity Rabi oscillations despite charge noise.
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Using a spin-triplet encoding to enhance shuttling fidelities in Si/SiGe quantum wells
A spin-triplet encoding based on valley-singlet states makes shuttling fidelities in Si/SiGe quantum wells higher and more robust to small valley splittings by suppressing Landau-Zener excitations.
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Smooth velocity shuttling for suppressing valley excitations in disordered Si/SiGe quantum dots
A Tukey-window-based smooth velocity shuttling protocol reduces valley excitations and average spin infidelity in disordered Si/SiGe quantum dots via analytical design and statistical simulations.
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Singlet-triplet oscillations in multivalley Si double quantum dots
Theoretical expressions for singlet return probability in multivalley Si double quantum dots near spin-valley resonances are derived, accounting for valley occupations, and validated against experiments to map valley ...
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