Psience Quest

Quote:In designing their experiment, the researchers sought to overcome three key problems: the idea that loss and noise make detection unreliable (the detection loophole), the idea that any communication that affects Alice’s and Bob’s measurement choices makes the measurement cheatable (the locality loophole), and the idea that a measurement-setting choice that is not “truly free and random” makes the result able to be controlled by a hidden cause in the common past (the freedom-of-choice loophole).

To address the first problem, Li and his colleagues demonstrated that their setup achieved a sufficiently low level of loss and noise by comparing measurements made at the start and end of the photon’s journey. To address the second, they built the experimental setup with space-like separation between the events of measurement setting choice. To address the third, they based their measurement-setting choices on cosmic photon behavior from 11 years earlier, which offers high confidence that nothing in the particles’ shared past – for at least the past 11 years – created a hidden variable affecting the outcome.

Combining theoretically calculated predictions with experimental results, the researchers were able to demonstrate quantum interactions between the entangled photon pairs with a high degree of confidence and fidelity. Their experiment thus provides robust evidence that quantum effects, rather than hidden variables, are behind the particles’ behavior.