Progress on accurate measurement of the Planck constant: Watt balance and counting atoms <xref ref-type="fn" rid="cpb141896fn1">*</xref>

Progress on accurate measurement of the Planck constant: Watt balance and counting atoms *

Li Shi-Song^a),^b),^†, Zhang Zhong-Hua^b),^‡, Zhao Wei^a), Li Zheng-Kun^b), Huang Song-Ling^a)

Fig. 13. Interferometers to measure the diameter of spheres. a Optical configuration in Saunders' interferometer, b optical configuration in the NMIJ interferometer, and c optical configuration in the PTB interferometer.