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Physicist's weird reverse-causality experiment goes in a new direction

Image: John Cramer
Scott Eklund / Seattle P-I file
Image: John Cramer
Since 2007, University of Washington physicist John Cramer has been working with lasers and mirrors to conduct experiments aimed at demonstrating whether causality can appear to go backward in time, as observed in a specific reference frame.Scott Eklund / Seattle Post-Intelligencer file

A physicist who has been looking for evidence that causality can go backward in time says he's making progress on nailing down the theoretical foundations for such quantum weirdness.

For years, the University of Washington's John Cramer has been trying to set up an experimental apparatus that would demonstrate what's known as "quantum nonlocal communication" — a characteristic of quantum mechanics that implies what you do to one entangled particle could affect what happens to a different particle earlier in time.

When Cramer started working on the crowdfunded experiment in 2007, he expected either to find evidence of such retrocausality — which would blow our minds — or to find out that subtle quantum effects kept spoiling the experiment.

So far, Cramer's own experiments have played out according to the latter, less exciting scenario. But the physicist says he's been having "very fruitful discussions" with Anton Zeilinger and his colleagues at the Institute for Quantum Optics and Quantum Information in Vienna. Like Cramer, Zeilinger is a pioneer in the study of quantum physics' spooky implications, including retrocausality.

"I learned a lot," Cramer told NBC News in an email. "Result: After returning to Seattle, I was able to develop quantum mechanical calculations that reproduce the unpublished data of Zeilinger's group in testing an entangled photon setup similar to mine. These quantum calculations also point to a way of implementing nonlocal signaling."

Cramer said the new scheme differs significantly from his previous experimental setups and needs to be tested. "I'm presently working on generating funding for that test," he wrote.

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Alan Boyle is's science editor. Connect with the Cosmic Log community by "liking" the NBC News Science Facebook page, following @b0yle on Twitter and adding +Alan Boyle to your Google+ circles. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.