Electrical manipulation and detection of single electron spins in quantum dots

Kavli Institute of Nanoscience DelftApplied Science

Universal Phase Shift and Nonexponential Decay of Driven Single-Spin Oscillations

Applied Science

Entanglement of spin-orbit qubits induced by Coulomb interaction

Spin-orbit qubit (SOQ) is the dressed spin by the orbital degree of freedom through a strong spin-orbit coupling (SOC). We show that Coulomb interaction between two electrons in quantum dots located separately in two nanowires can efficiently induce quantum entanglement between two SOQs. But to achieve the highest possible value for two SOQs concurrence, strength of SOC and confining potential for the quantum dots should be tuned to an optimal ratio. The physical mechanism to achieve such quantum entanglement is based on the feasibility of the SOQ responding to the external electric field via an intrinsic electric dipole spin resonance

Indirect control of spin precession by electric field via spin-orbit coupling

Spin-orbit coupling (SOC) can mediate the electric-dipole spin resonance (EDSR) within an a.c. electric field. By applying a quantum linear coordinate transformation, we find that the essence of EDSR could be understood as a spin precession under an effective a.c. magnetic field induced by the SOC in the reference frame, which is following exactly the classical trajectory of this spin. Based on this observation, we find an upper limit for the spin-flipping speed in the EDSR-based control of spin. For two-dimensional case, the azimuthal dependence of the effective magnetic field can be used to measure the ratio of the Rashba and Dresselhaus SOC strengths

Controllable coupling and quantum correlation dynamics of two double quantum dots coupled via a transmission line resonator

We propose a theoretical scheme to generate a controllable and switchable coupling between two double-quantum-dot (DQD) spin qubits by using a transmission line resonator (TLR) as a bus system. We study dynamical behaviors of quantum correlations described by entanglement correlation (EC) and discord correlation (DC) between two DQD spin qubits when the two spin qubits and the TLR are initially prepared in X-type quantum states and a coherent state, respectively. We demonstrate that in the EC death regions there exist DC stationary states in which the stable DC amplification or degradation can be generated during the dynamical evolution. It is shown that these DC stationary states can be controlled by initial-state parameters, the coupling, and detuning between qubits and the TLR. We reveal the full synchronization and anti-synchronization phenomena in the EC and DC time evolution, and show that the EC and DC synchronization and anti-synchronization depends on the initial-state parameters of the two DQD spin qubits. It is shown that the initial quantum correlation may be suppressed completely when the evolution time approaches to the infinity in the presence of dissipation. These results shed new light on dynamics of quantum correlations