Quantum effects brought to light, and sight

Nature : Quantum effects are usually detected indirectly via precision instruments. Now Nicolas Gisin, of the University of Geneva in Switzerland, and colleagues have created a new test to see if the human eye can pick up signs of entanglement, writes Zeeya Merali for Nature. The researchers entangled two photons, sent one to a standard photon detector, and amplified the other, creating a light field of thousands of photons with the same quantum state. The humans in the experiment observed the same effects of entanglement that the photon detectors recorded. However, Gisin set up the experiment so that the state of the second, amplified photon was measured before amplification, thus breaking the entanglement. Both the human observers and the photon detectors were deceived into giving false positives by the effect known as the detection loophole: Some photons will always be lost during the experiment. The more photons involved, the more the effect is magnified—and the more the results for both human and mechanical detectors are distorted.