Department of Physics, McGill University, Montreal, Quebec, Canada H3A 2T8.
Phys Rev Lett. 2010 May 7;104(18):186803. doi: 10.1103/PhysRevLett.104.186803. Epub 2010 May 4.
We study theoretically transitions of a double quantum-dot qubit caused by nonequilibrium charge fluctuations in a nearby quantum point contact (QPC) used as a detector. We show that these transitions are related to the fundamental Heisenberg backaction associated with the measurement, and use the uncertainty principle to derive a lower bound on the transition rates. We also derive simple expressions for the transition rates for the usual model of a QPC as a mesoscopic conductor, with screening treated at the RPA level. Finally, numerical results are presented which demonstrate that the charge noise and shot noise backaction mechanisms can be distinguished in QPCs having nonadiabatic potentials. The enhanced sensitivity of the charge noise to the QPC potential is explained in terms of interference contributions similar to those which cause Friedel oscillations.
我们从理论上研究了由用作探测器的附近量子点接触（QPC）中的非平衡电荷涨落引起的双量子点qubit 的跃迁。我们表明，这些跃迁与与测量相关的基本海森堡反作用有关，并利用测不准原理得出跃迁率的下限。我们还为 QPC 的通常模型推导了跃迁率的简单表达式，其中在 RPA 水平上处理屏蔽。最后，给出了数值结果，这些结果表明，可以在具有非绝热势的 QPC 中区分电荷噪声和散粒噪声反作用机制。电荷噪声对 QPC 势的增强敏感性可以用类似导致弗里德尔振荡的干涉贡献来解释。
