Ray Chiao Faster Than Light Quanta?

http://www.dhushara.com/book/quantcos/qnonloc/qnonloc.htm

Faster than Light
Raymond Chiao, Paul Kwait, Aephraim Steinberg Scientific American Aug 93

"For experimentalists studying quantum mechanics, the fantastic often turns into reality. A recent example emerges from the study of a phenomenon known as nonlocality, or "action at a distance.' This concept calls into question one of the most fundamental tenets of modem physics, the proposition that nothing travels faster than the speed of light. An apparent violation of this proposition occurs when a particle at a wall vanishes, orily to reappear-almost instantaneously-on the other side. A reference to Lewis Carroll may help here. When Alice stepped through the looking glass, her movement constituted in some sense action at a distance, or nonlocality: her effortless passage through a solid object was instantaneous. The particle's behavior is equally odd. If we attempted to caladate the particle's average velocity, we would find that it exceeded the speed of h&t. Is this possible? Can one of the most famous laws of modern physics be breached with impunity? Or is there something wrong with our conception of quantum mechanics or with the idea of a 'traversal velocity"? To answer such questions, we and several other workers have recently conducted many optical experiments to investigate some of the manifestations of quantum nonlocality. In particular we focus on three demonstrations of nonlocal effects. In the first example, we 'race' two photons, one of which must move through a 'wall.' In the second instance, we look at how the race is timed, showing that each photon travels along the two different race paths simultaneously. The final experiment reveals how the simultaneous behavior of photon twins is coupled, even if the twins are so far apart that no signal has time to travel between them. ...

So is Einstein's theory of relativity in danger? Astonishingly, no, because there is no way to use the correlations between particles to send a signal faster than light. The reason is that whether each photon reaches its detector or instead uses the down exit port is a random result. Only by comparing the apparently random records of counts at the two detectors, necessarily bringing our data together, can we notice the nonlocal correlations. The principles of causality remain inviolate.

Science-fiction buffs may be saddened to learn that faster-than-hght communication still seems impossible. But several scientists have tried to make the best of the situation. They propose to use the randomness of the correlations for various cipher schemes. Codes produced by such quantum cryptography systems would be absolutely unbreakable [see "Quantum Cryptography," by Charles H. Bennett, G Brassard and Artur D. Ekert; Scientific American, October 1992]. We have thus seen nonlocality in three different instances. First, in the process of tunneling, a photon is able to somehow sense the far side of a barrier and cross it in the same amount of time no matter how thick the barrier may be. Second, in the high-resolution timing experiments, the cancellation of dispersion depends on each of the two photons having traveled both paths in the interferometer. Finally, in the last experiment discussed, a nonlocal correlation of the energy and time between two photons is evidenced by the photons' coupled behavior after leaving the interferometers. Although in our experiments the photons were separated by only a few feet, quantum mechanics predicts that the correlations would have been observed no matter how far apart the two interferometers were. Somehow nature has been clever enough to avoid any contradiction with the notion of causality. For in no way is it possible to use any of the above effects to send signals faster than the speed of light. The tenuous coexistence of relativity, which is local, and quantum mechanics, which is nonlocal, has weathered yet another storm."

However, this ignores "signal nonlocality" that would violate this limit of quantum theory.

Subquantum Information and Computation
Antony Valentini
(Submitted on 11 Mar 2002 (v1), last revised 12 Apr 2002 (this version, v2))
"It is argued that immense physical resources - for nonlocal communication, espionage, and exponentially-fast computation - are hidden from us by quantum noise, and that this noise is not fundamental but merely a property of an equilibrium state in which the universe happens to be at the present time. It is suggested that 'non-quantum' or nonequilibrium matter might exist today in the form of relic particles from the early universe. We describe how such matter could be detected and put to practical use. Nonequilibrium matter could be used to send instantaneous signals, to violate the uncertainty principle, to distinguish non-orthogonal quantum states without disturbing them, to eavesdrop on quantum key distribution, and to outpace quantum computation (solving NP-complete problems in polynomial time)."