Nuclear State Preparation via Landau-Zener-Stueckelberg transitions in Double Quantum Dots

Abstract

We theoretically model a nuclear-state preparation scheme that increases the coherence time of a two-spin qubit in a double quantum dot. The two-electron system is tuned repeatedly across a singlet-triplet level-anticrossing with alternating slow and rapid sweeps of an external bias voltage. Using a Landau-Zener-Stueckelberg model, we find that in addition to a small nuclear polarization that weakly affects the electron spin coherence, the slow sweeps are only partially adiabatic and lead to a weak nuclear spin measurement and a nuclear-state narrowing which prolongs the electron spin coherence. This resolves some open problems brought up by a recent experiment [D. J. Reilly et al., Science 321, 817 (2008).]. Based on our description of the weak measurement, we simulate a system with up to n=200 nuclear spins per dot. Scaling in n indicates a stronger effect for larger n.

4.1 pages, 2 figures

References in corpus (5)

• Hyperfine interaction in a quantum dot: Non-Markovian electron spin dynamics
• Singlet-triplet decoherence due to nuclear spins in a double quantum dot
• Dynamic Nuclear Polarization with Single Electron Spins
• Universal set of quantum gates for double-dot spin qubits with fixed interdot coupling
• Degenerate Landau-Zener model: Exact analytical solution

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