Limits...
Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs.

Botzem T, McNeil RP, Mol JM, Schuh D, Bougeard D, Bluhm H - Nat Commun (2016)

Bottom Line: Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence.However, this effect disappears for appropriate field directions.Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor.

View Article: PubMed Central - PubMed

Affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.

ABSTRACT
Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III-V nanowires.

No MeSH data available.


Related in: MedlinePlus

B-field direction dependence.Echo amplitude at 300 mT as a function of separation time for different in-plane magnetic field directions θ, with 0° corresponding to the [110] direction. Curves are offset for clarity. At 45°, parallel to the crystallographic [100] axis, the coherence time is enhanced as quadrupolar couplings are suppressed. When rotating the field, a g-factor anisotropy leads to oscillations, associated with the three different nuclear Larmor frequencies. A semi-classical model (solid line) is used to fit the data (dots).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4835533&req=5

f2: B-field direction dependence.Echo amplitude at 300 mT as a function of separation time for different in-plane magnetic field directions θ, with 0° corresponding to the [110] direction. Curves are offset for clarity. At 45°, parallel to the crystallographic [100] axis, the coherence time is enhanced as quadrupolar couplings are suppressed. When rotating the field, a g-factor anisotropy leads to oscillations, associated with the three different nuclear Larmor frequencies. A semi-classical model (solid line) is used to fit the data (dots).

Mentions: The Hahn echo amplitude as a function of separation time is shown in Fig. 2 for different in-plane field directions θ between the [110] and the axes (Methods). Indeed, a factor two longer coherence is seen for θ=45°, parallel to the [100] (or [010]) direction. Apart from this enhancement, another oscillatory modulation appears, reaching a maximum at the same angle.


Quadrupolar and anisotropy effects on dephasing in two-electron spin qubits in GaAs.

Botzem T, McNeil RP, Mol JM, Schuh D, Bougeard D, Bluhm H - Nat Commun (2016)

B-field direction dependence.Echo amplitude at 300 mT as a function of separation time for different in-plane magnetic field directions θ, with 0° corresponding to the [110] direction. Curves are offset for clarity. At 45°, parallel to the crystallographic [100] axis, the coherence time is enhanced as quadrupolar couplings are suppressed. When rotating the field, a g-factor anisotropy leads to oscillations, associated with the three different nuclear Larmor frequencies. A semi-classical model (solid line) is used to fit the data (dots).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4835533&req=5

f2: B-field direction dependence.Echo amplitude at 300 mT as a function of separation time for different in-plane magnetic field directions θ, with 0° corresponding to the [110] direction. Curves are offset for clarity. At 45°, parallel to the crystallographic [100] axis, the coherence time is enhanced as quadrupolar couplings are suppressed. When rotating the field, a g-factor anisotropy leads to oscillations, associated with the three different nuclear Larmor frequencies. A semi-classical model (solid line) is used to fit the data (dots).
Mentions: The Hahn echo amplitude as a function of separation time is shown in Fig. 2 for different in-plane field directions θ between the [110] and the axes (Methods). Indeed, a factor two longer coherence is seen for θ=45°, parallel to the [100] (or [010]) direction. Apart from this enhancement, another oscillatory modulation appears, reaching a maximum at the same angle.

Bottom Line: Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence.However, this effect disappears for appropriate field directions.Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor.

View Article: PubMed Central - PubMed

Affiliation: JARA-Institute for Quantum Information, RWTH Aachen University, D-52074 Aachen, Germany.

ABSTRACT
Understanding the decoherence of electron spins in semiconductors due to their interaction with nuclear spins is of fundamental interest as they realize the central spin model and of practical importance for using them as qubits. Interesting effects arise from the quadrupolar interaction of nuclear spins with electric field gradients, which have been shown to suppress diffusive nuclear spin dynamics and might thus enhance electron spin coherence. Here we show experimentally that for gate-defined GaAs quantum dots, quadrupolar broadening of the nuclear Larmor precession reduces electron spin coherence by causing faster decorrelation of transverse nuclear fields. However, this effect disappears for appropriate field directions. Furthermore, we observe an additional modulation of coherence attributed to an anisotropic electronic g-tensor. These results complete our understanding of dephasing in gated quantum dots and point to mitigation strategies. They may also help to unravel unexplained behaviour in self-assembled quantum dots and III-V nanowires.

No MeSH data available.


Related in: MedlinePlus