Fig. 1. Diagram of phase detection between quantum system and microwave system in fountain clock

Fig. 2. Influence of LO on stability of fountain clock under different conditions. (a) T_C=2.8 s,T=0.56 s, and τ_p=40 ms; (b) Δν=1 Hz, T=0.56 s, and τ_p=40 ms

Fig. 3. Chain setup of microwave system of ⁸⁵Rb fountain clock

Fig. 4. Power spectrum of microwave signal in range of 1 MHz (insert is power spectrum in range of 100 kHz)

Fig. 5. Absolute phase noise of microwave system

Fig. 6. Experimental setup used for measurement of phase noise

Fig. 7. Residual phase noises of some key components in microwave frequency synthesizer

Fig. 8. Phase noise of microwave synthesizer