A quantum impedance standard having an insignificant, experimentally verified frequency dependence

Abstract

Recently we have published a novel double-shield configuration of quantum Hall devices to eliminate the effect of all presently known ac losses within 3×10 −9 kHz −1 . Now we have further verified the double-shielding technique by supporting the experimental findings with a model. This model indicates that it should be possible to reduce the frequency dependence to less than 1×10 −9 kHz −1 , which would be better than our ultimate measuring limit and much better than our calculable impedance artefacts. Thereby, the ac quantum Hall impedance closely approaches a perfect quantum standard.

The ac quantum Hall resistance as an electrical impedance standard and its role in the SI

“…It is attributed to ac losses in the GaAs substrate and is of the order of a few parts in 10 8 per kHz [20,82]. This means that the gating method is not exact and has a residual frequency dependence similar to the extrapolation [84], with the permission of the IEEE, copyright © 2010.) method [1].…”

“…For clarity, only the defining potential contacts are shown provided with bond wires and the multiple-series connections are not shown. (Reproduced from[84], with the permission of the IEEE, copyright © 2010. )…”

The quantum Hall impedance standard

“…The uncertainty bars indicate type A and B contributions from the coaxial bridge. (The first results are also published in [20].) To prove a residual linear frequency dependence, linear leastsquare fits have been made.…”

“…The quantum Hall device is shown as if the shields were transparent, and the outer conductor of only one coaxial lead is drawn. From [20]. © 2010 IEEE.…”

“…Section 2 briefly repeats the basic double-shielding idea, in section 3 we develop a model for the very small frequency and current dependence of the quantum Hall resistance, and in section 4 we verify the model experimentally by comparing several different double-shielded devices. By doing so, we keep a promise given in [16,20]. Finally, some aspects relevant to practical implementations are discussed in the appendix.…”