Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Indistinguishable single-mode photons from spectrally engineered biphotons



Thomas Gerrits, Adriana E. Lita, Sae Woo Nam, Changchen Chen, Jane Heyes, Kyung-Han Hong, Jeffrey Shapiro, Franco N. Wong


We use pulsed spontaneous parametric down-conversion in KTiOPO4, with a Gaussian phasematching function and a transform-limited Gaussian pump, to achieve near-unity spectral purity in heralded single photons at telecommunication wavelength. Theory shows that these phase-matching and pump conditions are sufficient to ensure that a biphoton state with a circularly symmetric joint spectral intensity profile is transform limited and factorable. We verify the heralded- state spectral purity in a four-fold coincidence measurement by performing Hong-Ou-Mandel interference between two independently generated heralded photons. With a mild spectral filter we obtain an interference visibility of 98.4{+or-}1.1% which corresponds to a heralded-state purity of 99.2%. Our heralded photon source is potentially an essential resource for measurement-based quantum information processing and quantum network applications.
Optics Express


quantum interference, indistinguishable photons, spontaneous parametric downconversion


Gerrits, T. , Lita, A. , Nam, S. , Chen, C. , Heyes, J. , Hong, K. , Shapiro, J. and Wong, F. (2019), Indistinguishable single-mode photons from spectrally engineered biphotons, Optics Express, [online], (Accessed May 20, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created April 15, 2019, Updated July 9, 2019