Single hole spin relaxation probed by fast single-shot latched charge sensing

Abstract

Hole spins have recently emerged as attractive candidates for solid-state qubits for quantum computing. Their state can be manipulated electrically by taking advantage of the strong spinorbit interaction (SOI). Crucially, these systems promise longer spin coherence lifetimes owing to their weak interactions with nuclear spins as compared to electron spin qubits. Here we measure the spin relaxation time T 1 of a single hole in a GaAs gated lateral double quantum dot device. We propose a protocol converting the spin state into long-lived charge configurations by the SOI-assisted spin-flip tunneling between dots. By interrogating the system with a charge detector we extract the magnetic-field dependence of T 1 ∝ B −5 for fields larger than B = 0.5 T, suggesting the phonon-assisted Dresselhaus SOI as the relaxation channel. This coupling limits the measured values of T 1 from~400 ns at B = 1.5 T up tõ 60 μs at B = 0.5 T.

Electrically tunable effective g-factor of a single hole in a lateral GaAs/AlGaAs quantum dot

“…At this detuning, without strong hybridization the energies of the left-dot orbitals of each spin would be higher than their right-dot counterparts, making it an energy blockade condition, and no current could flow. It should be noted that in our previous study 20 we found that the rate of tunneling from GS into the drain (dashed arrow) is smaller than that from ES1 (solid arrow). This is because the tunneling barrier is not rectangular but is wider (narrower) at lower (higher) energies.…”

“…It is written on the basis of the four spin states of the DQD, L * j i, L + j i, R * j i, and R + j i, i.e., the left (L) and right (R) dot orbitals with spin up (*) and down (+). The interdot coupling is accounted for by the tunneling matrix elements t N (spin conserving) and t F (spin flipping, resulting from the SOIs) 20,32,33 . The diagonal terms represent the onsite energies, determined by gate voltages and the magnetic field through the Zeeman energy E Z ¼ g à μ B B, where g à is the bulk g-factor and μ B is the Bohr magneton.…”

“…Here we demonstrate an electrically tunable effective g-factor, g eff , in a lateral gated GaAs double quantum dot (DQD) confining one hole 20,[31][32][33] in the strong interdot coupling regime. In this system, the spin-flip tunneling due to strong SOI 20,33 introduces orbital (charge-transfer) effects.…”

“…Here we demonstrate an electrically tunable effective g-factor, g eff , in a lateral gated GaAs double quantum dot (DQD) confining one hole 20,[31][32][33] in the strong interdot coupling regime. In this system, the spin-flip tunneling due to strong SOI 20,33 introduces orbital (charge-transfer) effects. Consequences of strong level hybridization have been investigated previously in electron devices, where spin relaxation hotspots were detected in Si-based single dots 34 and GaAs double dots 35 , and valley orbit mixing effects were explored in Si dots 36 .…”

“…However, a side effect of the increased SOI may result in a shorter hole spin relaxation time T 1 , as this process is brought about by phonon-assisted SOI. Recently, T 1 in the GaAs gated hole device was measured and shown to be somewhat shorter than that in electron-based GaAs devices 20 . Nonetheless, the advantage of hole-based devices lies in the fact that holes interact more weakly with nuclear spins than electrons 21,22 .…”