Spin–orbit qubit in a semiconductor nanowire

Abstract

Nanowires can serve as one-dimensional templates for scalable qubit registers. Unique to nanowires is the possibility to easily vary the material even during wire growth. 5Such flexibility can be used to design wires with suppressed decoherence and push semiconductor qubit fidelities towards error-correction levels. Furthermore, electrical dots can be integrated with optical dots in p-n junction nanowires. 6 The coherence times achieved here are sufficient for the conversion of an electronic qubit into a photon, the flying qubit, for long-distance quantum communication. Figure 1a shows a scanning electron microscope image of our nanowire device. Two electrodes, source and drain, are used to apply a voltage bias of 6 mV across the InAs nanowire. Voltages applied to five closely spaced narrow gates underneath the nanowire

Circuit quantum electrodynamics with a spin qubit

“…For example, the |⇑⇑> state cannot tunnel to S(0,2) due to Pauli exclusion. Modulation of the confinement potential with a gate voltage results in spin-orbit-driven EDSR transitions that lift the Pauli blockade [13,29]. In Fig.…”

“…The ground state with two-electrons in the right quantum dot is the singlet S(0,2). At negative detuning, the four relevant spin-orbital states are |⇑⇑>, |⇓⇓>, |⇑⇓>, and |⇓⇑> [13]. The level diagram is similar to a GaAs singlet-triplet spin qubit, with a key difference being that the g-factors for the two spins can vary significantly [3].…”

“…We observe two resonance conditions corresponding to single spin rotations in the left and right quantum dot, with g-factors of 8.2 and 10.6 [13]. Around = 0, the DQD has a spin state dependent dipole moment that allows spin state readout via the superconducting cavity [30].…”

Dephasing due to Nuclear Spins in Large-Amplitude Electric Dipole Spin Resonance

“…In conclusion, we have characterized the dephasing induced by the hypefine interaction in largeamplitude EDSR, and we showed that transverse fluctuations of the Overhauser field are likely to play an important role in this regime, recently achieved experimentally. It should be mentioned that also other dephasing sources were suggested for EDSR, such as paramagnetic impurities, charge noise, and photon-assisted tunneling [9,10,12]. In the absence of clear evidence (or specific predictions) about these alternative mechanisms, our theory offers further means to test if nuclear spins are indeed the dominant effect, e.g., through a detailed analysis of T R as function of both drive and detuning.…”

“…The resulting power-law decay and a universal π/4 phase shift of the Rabi oscillations were accurately verified [11], confirming the predominance of nuclear spins over other sources of dephasing. While EDSR experiments were also generally interpreted assuming a power-law decay, the expected t −1/2 dependence is violated at the larger values of the drive [9,10,12]. Especially, Ref.…”