62 P H V SIC S OF THE IMPOSSIBLE
Did information really travel faster than light? Was Einstein wrong
about the speed of light being the speed limit of the universe? Not
really. Information did travel faster than the speed of light, but the information was random, and hence useless. You cannot send a real
message, or Morse code, via the EPR experiment even if information
is traveling faster than light.
Knowing that an electron on the other side of the universe is spinning down is useless information. You cannot send today's stock quotations via this method. For example, let's say that a friend always
wears one red and one green sock, in random order. Let's say you examine one leg, and the leg has a red sock on it. Then you know, faster
than the speed of light, that the other sock is green. Information actually traveled faster than light, but this information is useless. No signal
containing nonrandom information can be sent via this method.
For years the EPR experiment was used as an example of the resounding victory of the quantum theory over its critics, but it was a
hollow victory with no practical consequences. Until now.
QUANTUM
TELEPORTATION
Everything changed in 1993, when scientists at IBM, led by Charles
Bennett, showed that it was physically possible to teleport objects, at
least at the atomic level, using the EPR experiment. (More precisely,
they showed that you could teleport all the information contained
within a particle.) Since then physicists have been able to teleport photons and even entire cesium atoms. Within a few decades scientists
may be able to teleport the first DNA molecule and virus.
Quantum teleportation exploits some of the more bizarre properties of the EPR experiment. In these teleportation experiments physicists start with two atoms, A and C. Let's say we wish to teleport
information from atom A to atom C. We begin by introducing a third
atom, B, which starts out being entangled with C, so B and C are coherent. Now atom A comes in contact with atom B. A scans B, so that
Did information really travel faster than light? Was Einstein wrong
about the speed of light being the speed limit of the universe? Not
really. Information did travel faster than the speed of light, but the information was random, and hence useless. You cannot send a real
message, or Morse code, via the EPR experiment even if information
is traveling faster than light.
Knowing that an electron on the other side of the universe is spinning down is useless information. You cannot send today's stock quotations via this method. For example, let's say that a friend always
wears one red and one green sock, in random order. Let's say you examine one leg, and the leg has a red sock on it. Then you know, faster
than the speed of light, that the other sock is green. Information actually traveled faster than light, but this information is useless. No signal
containing nonrandom information can be sent via this method.
For years the EPR experiment was used as an example of the resounding victory of the quantum theory over its critics, but it was a
hollow victory with no practical consequences. Until now.
QUANTUM
TELEPORTATION
Everything changed in 1993, when scientists at IBM, led by Charles
Bennett, showed that it was physically possible to teleport objects, at
least at the atomic level, using the EPR experiment. (More precisely,
they showed that you could teleport all the information contained
within a particle.) Since then physicists have been able to teleport photons and even entire cesium atoms. Within a few decades scientists
may be able to teleport the first DNA molecule and virus.
Quantum teleportation exploits some of the more bizarre properties of the EPR experiment. In these teleportation experiments physicists start with two atoms, A and C. Let's say we wish to teleport
information from atom A to atom C. We begin by introducing a third
atom, B, which starts out being entangled with C, so B and C are coherent. Now atom A comes in contact with atom B. A scans B, so that