The quantum anomalous Hall effect (QAHE), first observed in a magnetic topological insulator Cr/V-doped (Bi,Sb)2Te3 [1], holds promise as a disruptive innovation in quantum metrology, for its potential to define a new generation of quantum standards of resistance [2,3]. Indeed, one of the goals of modern metrology is to combine various standards into a so-called quantum electrical metrology toolbox, a single measurement apparatus that can perform quantum resistance, voltage and current metrology, i.e. a universal electrical standard. Conventional quantum standards of resistance rely on the integer quantum Hall effect. The large external magnetic field needed to establish the quantum Hall effect makes a quantum standard of voltage (based on the a.c. Josephson effect) inoperable [4]. This is where QAHE can save the day and enable combined standards by providing resistance quantization at zero external magnetic field [3]. This is also important in the context of the recent redefinition of the SI system, as the unit of mass, the kilogram, is now defined based on to the Planck's constant (h). Given that a direct experimental access to the value of h with sufficient precision is challenging, alternative methods based on the simultaneous measurements of the quantized resistance and voltage further gained in significance (quantized resistance gives a value of h/e^2 and voltage a value of 2e/h, which combined allows to obtain both e and h, e being the elementary charge). In this talk I will discuss our recent realization of a zero external magnetic field quantum standard of resistance using the QAHE, with a relative quantization precision and accuracy of a few parts-per-billion (or 10^-9) [3], for the first time surpassing the relevant thresholds for a quantum resistance standard. While demonstrating that the effect can indeed be used in metrology, this was realized under very challenging experimental conditions (extremely low temperature and low electrical current). The effect will need to be made significantly more robust to enable mainstream metrology applications, and I will show why our recent results give us confidence this is possible [5,6].

[1] C.-Z. Chang et al.. Science 340, 167-170 (2013).

[2] Y. Okazaki et al.. Nature Physics 18, 25-29 (2022).

[3] D. K. Patel, K. M. Fijalkowski et al. Nature Electronics 7, 1111-1116 (2024).

[4] J. Brun-Picard et al. Physical Review X 6, 041051 (2016).

[5] K. M. Fijalkowski et al. Nature Communications 12, 5599 (2021).

[6] K. M. Fijalkowski et al. Nature Electronics 7, 438-443 (2024).