1: We have revised the manuscript for changes, including those not evident from the tracking.

2: The correct affiliation for the first three authors is:
"Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543, Singapore"


3: At line 17, add the following heading:
"INTRODUCTION"

at line 43 add the following heading:
"SOURCE OF HERALDED SINGLE PHOTONS"

at line 113 add the following heading:
"MEASUREMENT OF THE FIELD OF HERALDED PHOTONS"

at line 175 add the following heading:
"DISCUSSION OF RESULTS AND CONCLUSION"

at line 226 add the following heading:
"AKNOWLEDMENTS"

4: In line 10 replace: "$g^{(2)}(0)\leq0.03$" with: "a value for the second order correlation at zero delay less than 0.03"

5: We have checked the manuscript for all S1/2, P1/2, P3/2, and D3/2.

6: We checked for all D$_{i1}$ and D$_{i2}$.

7: In the caption of figure 1, please replace the text:
"Setup of the heralded single photon source. Polarizers (P1, P2, Pi, Ps) and interference filters (Fi, Fs) separate the signal and idler photons from the residual pump light."
with
"Setup of the heralded single photon source. Polarizers (P1, P2, Pi, Ps) and interference filters (Fi, Fs) separate the signal and idler photons from the residual pump light before coupling into single mode fibers (SMF)."
and also replace the text reading:
"Signal photons detected by an avalanche photodiode (APD) trigger a Hanbury-Brown–Twiss measurement between idler photons distributed to two detectors, Di1 and Di2, via a 50:50 fiber beam splitter (BS)."
with:
"Signal photons detected by Ds, an avalanche photodiode (APD), trigger a Hanbury-Brown–Twiss measurement between idler photons distributed to two detectors, Di1 and Di2, via a 50:50 fiber beam splitter (BS)."

8: No, 2 is the correct number!

9: PBS2 is already mentioned in the text.

10: In the caption of fig.3 please replace: "... is amplified and recorded ..." with "... is amplified by a transimpedance amplifier (G) and recorded..."

11: The correct year for the third edition is 2000, not 2003.

FQ: Please add the following reference code to the