Extended Data Fig. 4. Coherence preservation during erasure detection.

a,b, We prepare the Bell state $∣{\mathrm{\Psi }}^{+}⟩$, and measure the relevant populations for Bell fidelity extraction P_gr + P_rg and P_gg (after an extra π pulse) as a function of holding time. We perform a 2π pulse in the middle of the holding time to get rid of dephasing effect due to e.g. Doppler effect. We present the results with (blue) and without (red) performing the erasure imaging during the holding time. We observe no significant difference between the two conditions, which suggests that the erasure detection imaging light, in principle, does not destroy the coherence of the Bell state.