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.

Direct generation of three-photon polarization entanglement



Deny Hamel, Krister Shalm, Hannes Hubel, Aaron J. Miller, Francesco F. Marsili, Varun Verma, Richard Mirin, Sae Woo Nam, Kevin Resch, Thomas Jennewein


Non-classical states of light are of fundamental importance for emerging quantum technologies. All optics experiments producing multi-qubit entangled states have until now relied on outcome post-selection, a procedure where only the measurement results corresponding to the desired state are considered. This method severely limits the usefulness of the resulting entangled states. Here, we show the direct production of polarization-entangled photon triplets by cascading two entangled downconversion processes. Detecting the triplets with high eciency superconducting nanowire single-photon detectors allows us to fully characterize them through quantum state tomography. We use our three-photon entangled state to demonstrate the ability to herald Bell states, a task which was not possible with previous three-photon states, and test local realism by violating the Mermin and Svetlichny inequalities. These results represent a signi cant breakthrough for entangled multi-photon state production by eliminating the constraints of outcome post-selection, providing a novel resource for optical quantum information processing.


Entanglement, Photons, Single-photon detectors


Hamel, D. , Shalm, K. , Hubel, H. , Miller, A. , Marsili, F. , Verma, V. , Mirin, R. , Nam, S. , Resch, K. and Jennewein, T. (2014), Direct generation of three-photon polarization entanglement, Science (Accessed April 18, 2024)
Created April 27, 2014, Updated October 12, 2021