Penetration of the wave function into a classically forbidden region

Teleportation: or the penetration of the wave function into a classically forbidden region by Ian Woolf

The Theory and Practice of Teleportation by Larry Niven: "Definition:
Teleportation is any method of moving from point to point in negligible
time. Over short distances we will take lightspeed as negligible. Over
longer distances (interplanetary and interstellar) we will require
infinite or near-infinite speed."

From Harry Harrison's matter transmitters to Alfred Bester's Jaunts,
teleportation has long been a favourite in science fiction stories.
Some authors, like Larry Niven, take great care to try and get all the
scientific implications right, while others like Star Trek
misunderstand them.

The traditional Newtonian method is matter transmission or "beaming".
The matter transmission has usually been visualized as a breaking up of
the original substance by scanning the molecules and atoms one at a
time, then blasting out this scanning signal to be rebuilt at the
receiving end.

In Poul Anderson's The Enemy Stars, a side effect is that the body is
vapourized, so that one winds up with a complete record of the
passenger plus a cloud of superheated plasma. The gas is sucked through
a grid to be stored in a matter reserve, to await the next incoming
signal. The record of the passenger is sent across space, by radio. A
receiver picks it up and uses it, plus the plasma in its matter reserve
to reconstruct the passenger. As Niven says, "I wouldn't ride in one of
the goddamned things." The earliest recorded story of a matter
transmitter was in Edward Page Mitchell's "The Man Without a Body" in
1877, where a scientist invents a machine that breaks down the atoms of
a cat and transmits them by wire to the receiver, where the animal is
reassembled alive and well. He tries it upon himself, but the battery
dries up before he can transmit more than just his head. Technical
problems are loss of power, signal interference, intervening dust and
gas, and red and blue shifts due to gravity and relative velocities.

Sometimes the signal is stored rather than being broadcast which leads
to fun and games when the same person is rebuilt over and over again
from his recordings. Also you can store and copy the passenger's
record, beam it to several receivers, and end up with multiple copies
of people. If we advance that technique, and the original mug doesn't
need to get vapourized, then you get to go and stay at the same time.
This would lead logically to related technologies such as matter
replicators, and resurrection. After all we don't, by radio or TV send
images or sounds anywhere, they remain at their point of origin.

World without distance by Arthur C. Clarke "Can any words or
description span the gulf between the photograph of a man - and the man
himself?"

However Quantum physics suggests that there is a good explanation for
the destruction of the original. Measuring a quantum system changes
what you are measuring. The act of observation will change the original
state to something unpredictable, so you'll have your information, but
the original state of the brain has been scrambled.
There are two distinct physical states of matter, definite-observed and
uncertain-unobserved, what Greg Egan in "Quarantine" calls "smeared".
Making an observation of a smeared electron will change it. There are
many qualities that are incompatible, the measurement of one fuzzes the
other further into uncertainty. Quantum logic as might be used in human
brains and future computers, rely on the smeared state for their
computational power. Thus accurate copying of a complex quantum system
is impossible, and the attempt will change the system you are
attempting to copy.

Star Trek originally made use of this kind of system, although they
often went without receivers. The New Generation Star Trek have changed
the nature of their teleportation explanations through several
episodes. Scotty stores his signal in a pattern buffer and is revived
later. The possibilities for immortality are ignored. Crewmembers can
be reconstructed wrongly if their DNA is not recorded correctly. A
mistake in one episode causes Picard to beam in as a child due to
missing genes, hinting that the new transporter reconstructs them
according to their DNA, and not according to the positions of all the
atoms as did the old system. If so, all injuries, scars, and suntans
would disappear. A malfunction could then have interesting results. A
leather belt, cotton shirt, denim jeans could result in a cow being
reconstructed with you, cotton plants draped over your shoulder, hemp
plants draped around your loins and you with a hideous case of
indigestion.
Riker is beamed away from a station during heavy interference, and this
produces a second Riker, with the original left stranded on the
station. The original mysteriously grows the same beard as the
duplicate we are familiar with. Star Trek sometimes explains its
teleportation as displacement, where the passenger actually changes
location. For example Barclay in one episode becomes aware of transit
time and is bitten by creatures in the beam, and rescues people trapped
in the beam. This seems related to Anne McCaffrey's teleporting dragons
who travel "between" in some sort of otherspace.

In all known cases the laws of conservation of energy and momentum hold
rigorously. In Larry Niven's "The Alibi Machine" series the potential
energy of teleporting uphill is an important part of the story. When
teleporting uphill, potential energy is gained so that energy must be
lost somewhere else. People can get colder when teleporting uphill in
his story. The difference in angular momentum between different point's
on Earth's spherical spinning surface is taken into account with
momentum-damping buoys floating in harbours. Many other authors ignore
these necessities, particularly when the displacement is caused by
psychic means as in Bester's "The Stars My Destination" (Tiger Tiger).
Psychic teleportation in Vernor Vinge's "The Witling" takes these into
account with the person teleporting from water to absorb both the
difference in motion and the temperature difference harmlessly.

Relativistic uncertainty could be a problem over interstellar
distances. The more distant one's destination, the less certain is its
location in space and time. According to Einstein time runs at
different rates at different places in the Universe. Also everything
moves relative to everything else in space, so your destination is
constantly moving. In this case large computers and spaceships become a
necessity.

Quantum jumping is a mechanism for displacement. In modern electronics
tunnel diodes take an electron from here and put it there without
allowing it to occupy the intervening space, or as the textbooks drily
put it, "the penetration of the wave function into the classically
forbidden region." Scanning tunneling electron microscopes work on this
principle. An electric field applied to a metal tip so that the
electrons in the tip have enough energy to reach a metal surface
underneath for a short distance. However the electrons cannot exist in
the vacuum between the tip and the surface. A small current results
from the electrons tunneling out of the tip, teleporting from the tip
to the surface. No electron can be detected between the tip and the
surface. However macroscopic passengers would have to beware of
appearing in the midst of existing matter, and dying of embolism, or
worse. James H. Schmidtz in "The Lion Game" has a predator tricked
into teleporting into a hill, and exploding. Niven has the entire
contents of teleport booths swapped to avoid this problem, other
authors have vacuums created when you leave and air rushes away from
where you appear. Some authors simply say its impossible to teleport
unless the destination is empty.
In April 1995, photons were teleported across 12 centimetres in the
laboratory to send a signal at 4.7 times the speed of light using the
tunnel effect. Probability can be manipulated in some electronic
devices such as lasers, where the emission of light of one frequency by
one atom affects the probability of other atoms doing the same until
you have all the atoms behaving in step and you get coherent light.
Thus it may one day be possible to use this principle to get all the
atoms in a macroscopic body to teleport at the same time to the same
location.

References:

"Faster Than The Speed Of Light" by Julian Brown, New Scientist 1 April 1995

"The Theory and Practice of Teleportation" by Larry Niven, All the Myriad Ways

Quantum Mechanics by Alistair Rae 1990

Superforce by Paul Davies 1984

Profiles of the Future by Arthur C. Clarke 1973

The Visual Encyclopaedia of Science Fiction edited by Brian Ash, 1977