科研之友
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摘要
Exploiting the two-point measurement statistics, we propose a quantum measurement scheme of current with limited resolution of electron counting. Our scheme is equivalent to the full counting statistics in the long-time measurement with the ideal resolution, but is theoretically extended to take into account the resolution limit of actual measurement devices. Applying our scheme to a resonant level model, we show that the limited resolution of current measurement gives rise to a positive excess noise, which leads to a deviation from the Johnson-Nyquist relation. The deviation exhibits universal single-parameter scaling with the scaling variable Q = S-M/S-0, which represents the degree of the insufficiency of the resolution. Here, S-0 is the intrinsic noise, and S-M is the positive quantity that has the same dimension as S-0 and is defined solely by the measurement scheme. For the lack of the ideal resolution, the deviation emerges for Q < 1 as 2 exp[-(2 pi)(2)/Q] having an essential singularity at Q = 0, which followed by the square root dependence root Q/4 pi for Q >> 1. Our findings offer an explanation for the anomalous enhancement of noise temperature observed in Johnson noise thermometry.
- 出版日期2014-5-20
