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.

A significant-loophole-free test of Bell's theorem with entangled photons



Marissa Giustina, Marijn Versteegh, Soren Wengerowsky, Johannes Handsteiner, Armin Hochrainer, Kevin Phelan, Fabian Steinlechner, Johannes Koffler, Larsson Jan-Ake, Carlos Abellan, Waldimar Amaya, Valerio Pruneri, Morgan Mitchell, Joern Beyer, Thomas Gerrits, Adriana Lita, Krister Shalm, Sae Woo Nam, Thomas Scheidl, Rupert Ursin, Bernhard Wittmann, Anton Zeilinger


Local realism is the worldview in which physical properties of objects exist independently of measurement and where physical influences cannot travel faster than the speed of light. Bell's theorem states that this worldview is incompatible with the predictions of quantum mechanics, as is expressed in Bell's inequalities. Previous experiments convincingly supported the quantum predictions. Yet, every experiment performed to date required assumptions that provide loopholes for a local realist explanation. Here we report a Bell test that closes the most significant of these loopholes simultaneously. Using a well-optimized source of entangled photons, rapid setting generation, and highly efficient superconducting detectors, we observe a violation of a Bell inequality with high statistical significance.
Physical Review Letters


loophole free Bell test, local realism, fundamental tests of quantum mechanics, transition edge sensors


Giustina, M. , Versteegh, M. , Wengerowsky, S. , Handsteiner, J. , Hochrainer, A. , Phelan, K. , Steinlechner, F. , Koffler, J. , Jan-Ake, L. , Abellan, C. , Amaya, W. , Pruneri, V. , Mitchell, M. , Beyer, J. , Gerrits, T. , Lita, A. , Shalm, K. , Nam, S. , Scheidl, T. , Ursin, R. , Wittmann, B. and Zeilinger, A. (2015), A significant-loophole-free test of Bell's theorem with entangled photons, Physical Review Letters, [online],, (Accessed April 20, 2024)
Created December 15, 2015, Updated October 12, 2021