Tunable charge qubit based on barrier-controlled triple quantum dots

Abstract

We present a theoretical proposal of a tunable charge qubit, hosted in triple quantum dots. The manipulation is solely performed by changing the heights of the two potential barriers between the three dots, while the energy of all three dots are fixed. We have found that when the relative height of the two barriers are changed, the direction of the axis of rotation in performing single-qubit gates can be varied. On the other hand, the corresponding rotation speed can be tuned by raising or lowering the two barriers at the same time. Our proposal therefore allows for tunability of both the rotation axis and rotating speed for a charge qubit via all-electrical control, which may facilitate realization of quantum algorithms in these devices. arXiv:1805.04221v2 [cond-mat.mes-hall]

Theory on electron-phonon spin dehphasing in GaAs multi-electron double quantum dots

“…5 is a combinational effect of the changing rate of Γ ST and J as functions of β/ 1 + β 2 . More importantly, the merit figure for states associated with (1,3) and (1,7) are greater than those associated with (1,1). This indicates that multielectron quantum dots may offer advantages in electronphonon dephasing, which is the main result of this paper.…”

“…3(b) the range 0.05 < β/ 1 + β 2 < 0.10. We can see that while Γ ST increases monotonically with the hybridization ratio, the order of the results for states with mainly (1, 1), (1,3), and (1, 7) character changes. In particular, for β/ 1 + β 2 = 0 the dephasing rate for the state (1, 1) is the smallest, consistent with the unbiased case.…”

“…Secondly, for a given confinement strength, the dephasing rate is greatest for (1, 7) as more electrons imply larger integration from A φ as Appendix A shows, implying more channels of electron-phonon interaction. Similarly, the effect is intermediate for (1,3), and smallest for (1, 1). Thirdly, when x 0 and ω L are fixed, the dephasing rate is greater when dot R is larger (smaller ω R ) and smaller when dot R is smaller (larger ω R ).…”

“…Here we consider three unbiased cases with electron configurations (1, 1), (1,3), and (1, 7) with the first entry showing the number of electron in dot L and the second dot R. A schematic showing the latter two cases is shown in Fig. 1(b).…”

Suppression of Leakage for a Charge Qubit in Triangular Triple Quantum Dots

“…In the CQ qubit, an electron resides in a triple-quantum-dot system, giving rise to three electron states. In the lateral geometry, the tunneling between the two outermost dots are neglected, and one is left with only two barriers to address [20,23]. It is argued that if the energies of the two barriers can be kept equal for the duration of the operation, and the same can be done for the the energies of the two outmost dots, we are left with a decoherence free subspace against charge noise with which the fidelity may be substantially improved [20].…”