Skip to main content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.


The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

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
Created April 15, 2019, Updated July 9, 2019