Controlling a Nanowire Spin-Orbit Qubit via Electric-Dipole Spin Resonance

Abstract

A semiconductor nanowire quantum dot with strong spin-orbit coupling (SOC) can be used to achieve a spin-orbit qubit. In contrast to a spin qubit, the spin-orbit qubit can respond to an external ac electric field, an effect called electric-dipole spin resonance. Here we develop a theory that can apply in the strong SOC regime. We find that there is an optimal SOC strength η(opt)=√2/2, where the Rabi frequency induced by the ac electric field becomes maximal. Also, we show that both the level spacing and the Rabi frequency of the spin-orbit qubit have periodic responses to the direction of the external static magnetic field. These responses can be used to determine the SOC in the nanowire.

Spin-orbit qubit on a multiferroic insulator in a superconducting resonator

“…37 This Hamiltonian is equivalent to the one studied in Ref. 16, where a spin-orbit qubit was realized by virtue of an external magnetic field and the genuine Rashba/Dresselhaus SOC. Now we demonstrate the realization of a spin-orbit qubit by studying the low-energy bound states in the quantum dot.…”

“…[26][27][28] Several proposals for coupling spin-orbit qubits to superconducting cavities have been reported. 15,23,29,30 However, the spinorbit qubit invoking SOC requires an external static magnetic field, 12,13,16,18 which is not naturally compatible with superconducting cavities of high quality factors. 23 Therefore, a spin-orbit qubit without an external magnetic field is preferred for constructing a hybrid system.…”

“…9,10 Intuitively, the interplay between spin and orbit can arise from the spin-orbit coupling (SOC), e.g., the Rashba or Dresselhaus type, which couples the electron spin σ to the momentum p. The SOC-mediated EDSR has been widely studied in the literature. [11][12][13][14][15][16][17][18] Instead of invoking SOC, an alternative way to achieve the interplay between spin and orbit is coupling the electron spin σ to the coordinate r. This spin-coordinate coupling can be accomplished by, e.g., an inhomogeneous Zeeman-like interaction 15,[19][20][21][22][23] or a fluctuating hyperfine interaction. 24,25 Apart from coherent manipulation, scaling up the spinorbit-qubit architecture also involves quantum information storing and transferring.…”

Anisotropic exchange coupling in a nanowire double quantum dot with strong spin-orbit coupling

“…Indeed, a large Rabi frequency of ∼100 MHz was reported recently for single-qubit operations [21]. Interestingly, in the presence of strong SOC, the coupling between the spin-orbit qubit and the electric field depends nonlinearly on the SOC strength [22] and there is an optimal SOC where the Rabi frequency induced by an ac electric field becomes maximal [8]. Now, it becomes desirable to realize a controllable coupling between two spin-orbit qubits, in order to implement nontrivial (i.e., conditional) two-qubit operations.…”

“…Recently, a hybrid qubit, the spin-orbit qubit [6,7], was achieved in a nanowire quantum dot with strong spin-orbit coupling (SOC). A distinct advantage of this spin-orbit qubit is its manipulability via an electric field (an effect called electric-dipole spin resonance [6][7][8][9][10][11][12][13][14][15]) because a local electric field can be generated in experiments much more easily than a local magnetic field [16].…”