The claimed achievement of two Australian researchers in “teleporting” a stream of photons (light particles) from one side of a laboratory to the other, could have deep consequences for “quantum computing” and “quantum communications”, they say.
The experiment destroyed a laser-generated stream of photons carrying information and recreated it in a different place, apparently instantaneously. This immediately had lay commentators talking about “teleportation” of physical objects and even people in the style of a Star Trek transporter.
But the consequences for instant secure communication appear far closer at hand. Ping Koy Lam, one of the researchers at the Australian National University, says. While, over reasonable distances, instantaneous communication will not be significantly faster than the near-light-speed communication already possible through wires, fibres and microwaves, the hopes for secure communication appear far more important.
Since the communication does not exist on any material medium between the source and the destination, it is extremely difficult to intercept.
Even if intercepted, Lam says, the communication would be unintelligible to a third party, since it relates specifically to the properties of the subatomic particles at either end of the link.
The “teleportation” depends on a phenomenon called “quantum entanglement”, whereby, when a particle that does not spin (the definition of “spin” in this context is rather arcane) is split into two particles, they can each acquire an opposite spin. If the spin of one particle is subsequently changed, its separated mate instantaneously changes its own spin to keep the pair balanced, no matter how large the distance between them. Information is apparently transmitted faster than the speed of light.
Beyond that simplistic account, quantum entanglement dives into the kind of physics where “interpretation” and “philosophy” are spoken of rather than hard scientific theory. The phenomenon was and continues to be the subject of ferocious discussion among theoretical physicists the first of whom were Albert Einstein, of relativity fame, and Neils Bohr, who developed early models of the atom and pioneering "interpretations" of quantum theory.
Some aspects of quantum entanglement do appear to have practical uses, not only in communication, but in the innards of computers. By using the interaction between the quantum states (parameters like “spin”) of subatomic particles, logic gates, the basic ingredients of microchips, can be made far smaller and consume far less power than today’s chips.
Moreover, when done in a quantum way, certain calculations that are exponentially complex in ordinary computing (the time required for computation increases rapidly as the number of elements calculated increases) will become only “linear” (increasing in time in direct proportion with the number of elements). The familiar steeply rising exponential curve, becomes a gently sloping straight line. Thus sorts and searches of vast databases could, in theory, be done far more efficiently.
Unfortunately, perhaps, the class of calculations much speeded by quantum computing includes those required to “crack” conventional encryption algorithms.
So quantum entanglement, it appears, brings us gains and losses in the ability to keep our private messages private.
It will be many years before the principles are likely to be embodied in a saleable device which does non-trivial computing, physicists agree. However, there is hope for the prolongation, even the improvement, of Moore’s Law on the inexorable rise of computing power.
But a quantum Qantas taking us across the Tasman in an instant? Just a gleam in a physicist’s eye right now.