Coherent spin rotations in open driven double quantum dots

TL;DR

This paper investigates how combined DC and AC magnetic fields influence charge and spin behavior in double quantum dots, revealing mechanisms for coherent spin control and current blockade useful for quantum information applications.

Contribution

It introduces a detailed analysis of spin dynamics under crossed magnetic fields, demonstrating new methods for controlling and measuring spin states via tunneling current in quantum dots.

Findings

Coherent spin rotations occur in double quantum dots under specific magnetic conditions.

Electronic trapping in triplet states can be lifted by spin relaxation or Zeeman splitting differences.

Resonant bichromatic fields enable coherent superpositions and current blockade detection.

Abstract

We analyze the charge and spin dynamics in a DC biased double quantum dot driven by crossed DC and AC magnetic fields. In this configuration, spatial delocalization due to inter-dot tunnel competes with intra-dot spin rotations induced by the time dependent magnetic field, giving rise to a complicated time dependent behavior of the tunnelling current. When the Zeeman splitting has the same value in both dots and spin flip is negligible, the electrons remain in the triplet subspace (dark subspace) performing coherent spin rotations and the current does not flow. This electronic trapping is removed either by finite spin relaxation or when the Zeeman splitting is different in each quantum dot. In the first case, our results show that measuring the current will allow to get information on the spin relaxation time. In the last case, we will show that applying a resonant bichromatic magnetic field, the electrons become trapped in a coherent superposition of states and electronic transport is blocked. Then, manipulating AC magnetic fields, electrons are driven to perform coherent spin rotations which can be unambiguously detected by direct measurement of the tunneling current.