Because it’s hard to argue with people once involved in Nobel Prize-winning work, I take Warren Nagourney (University of Washington) at his word. At one time Nagourney assisted Hans Dehmelt, the UW scientist who won the 1989 Nobel Prize in physics. Now he’s working with John Cramer on a project so bizarre that, as this Seattle Post-Intelligencer story reports, he understands it only faintly.
That makes Centauri Dreams‘ chances of understanding it all but infinitesimal. And because the work involves the paradoxical quantum behavior called ‘entanglement’ and implies communicating information backwards in time, it also conjures up memories of another man one hesitates to challenge. It was Einstein who called certain weird quantum behaviors ‘spooky action at a distance’ and cultivated a continuing distaste for the paradoxes of quantum mechanics.
These are formidable scientists, but then so is Cramer, and in a way he seeks to confirm something Einstein said a long time ago. Einstein didn’t like the idea that entangled particles like photons could affect each other no matter how far apart they were in time or space. Didn’t a signal have to pass between them? The Einstein-Podolsky-Rosen paradox, which describes this behavior, was created just to showcase what seemed to be an absurd situation. How could a measurement made on one photon affect the other instantly no matter how far apart the two particles were?
Nonetheless, the evidence for entanglement seems strong. Let me quote Cramer from the article:
“If you do a measurement on one, it has an immediate effect on the other even if they are separated by light years across the universe…If one of the entangled photon’s trajectory tilts up, the other one, no matter how distant, will tilt down to compensate.”
Doesn’t communicating require a signal? Einstein thought so. He also knew that signals don’t move faster than the speed of light. Quantum theorists have found ways to make entanglement happen that don’t involve communicating, but Cramer thinks entangled particles do ‘talk’ to each other. It’s just that the communications can go backward as well as forward in time. And Cramer’s new experiment will test the proposition.
Read the article for experimental details. If Cramer is right and the experiment works, he may be able to show that a signal was received 50 microseconds before it was sent. And Cramer, ever far-sighted (he’s a science fiction writer as well as a scientist, and well known for his fine Alternate View columns in Analog), talks about implications like manipulating a Mars rover in real time — no speed of light delay.
Thanks to Tim Jones for reminding me about this experiment, and for making a good point that follows from it:
“I suppose the question would be whether to throw in the resources necessary to try and develop a single, killer technology like (quantum) teleportation that might solve the problem of long missions, or assume such research too financially risky and unlikely to succeeed, and press on regardless with the current paradigm.”
It’s always a tough call, and I think the answer remains that both avenues stay in play, though clearly, unless there are major breakthroughs, the longshot technologies will receive a minute portion of available funding. In terms of interstellar flight, we always bear in mind that the sudden insight may change everything, but in the meantime, we know the physics of forseeable missions (at least to nearby interstellar space) using sails and ‘Sundiver’ trajectories (a fine Gregory Benford coinage), about which more next week.