NIST physicist David Wineland adjusts an ultraviolet laser beam
used to manipulate ions in a high-vacuum "ion trap" used to 'teleport' the
quantum state of one atom to another.
Physicists at the Commerce Department's National Institute of
Standards and Technology (NIST) have demonstrated "teleportation" by
transferring key properties of one atom to another atom without using any
physical link, according to results reported in the June 17, 2004, issue of
the journal Nature.
Unlike the "beaming" of actual physical objects and people between
distant locations popularized in the Star Trek science fiction series, the
term "teleportation" is how physicists describe a transfer of "quantum
states" between separate atoms. The quantum state of an atom is a
description of such things as its energy, motion, magnetic field and other
The NIST experiments used laser beam manipulations to transfer quantum
states of one beryllium atom to another atom within a set of microscale
traps, with a 78 percent success rate. The technique may prove useful for
transporting information in quantum computers of the future, which could use
central processing elements smaller than a cube of sugar to carry out
massively complex computations that are currently impossible.
If they can be built, quantum computers-harnessing the strange
behavior of particles at the atomic scale-someday might be used for
applications such as code breaking of unprecedented power, optimizing
complex systems such as airline schedules, much faster database searching
and solving of complex mathematical problems, and even the development of
novel products such as fraud-proof digital signatures.
Teleportation takes place inside an ion trap made of gold
electrodes deposited onto alumina. The trap area is the horizontal opening
near the center of the image.
The NIST work and other research by the University of Innsbruck
reported in the same issue of Nature mark the first demonstrations of
teleportation using atoms. Systems using atoms are arguably the leading
candidate for storing and processing data in quantum computers.
Teleportation could increase computing speed and efficiency by linking
distant zones within a computer so that data could be processed by
physically separated quantum bits (or qubits, the quantum form of the
digital bits 1 and 0).
Quantum computing with atomic qubits requires manipulation of
information contained in the quantum states of the atoms. "It's hard to
quickly move qubits to share or process information. But using teleportation
as we've reported could allow logic operations to be performed much more
quickly," says NIST physicist David Wineland, leader of the NIST work.
The NIST group previously has demonstrated the building blocks for a
quantum computer based on atomic-ion traps. The new experiments, which are
computer controlled and perform teleportation in about 4 milliseconds,
incorporate most of the features required for large-scale information
processing systems using ion traps. In addition, the experiments are
relatively simple in design and could be used as part of a series of logical
operations needed for practical computing.
The demonstration described in the Nature paper exploited quantum
properties that are radically different from the properties observed in the
"normal" world. For example, ions can be manipulated into a special state
known as a "superposition" in which they literally can be in two places at
once. Similarly, they also can hold information representing more than one
number at once, a common property of all qubits. Ions also can be
"entangled" with each other, so that their behavior is related in
predictable ways, as if they were connected by an invisible force. Einstein
called this "spooky action at a distance."
The NIST experiments entangled a set of three ions, then destroyed the
quantum state in one ion and teleported it to another one. The properties
that were teleported included the "spin state" of the ion (up, down or a
superposition of the two), and the "phase" (which has to do with the
relative positions of the peaks and troughs of an ion's wave properties). A
clever approach was required because of another unusual feature of the
quantum world: measurements always alter quantum states (for example,
causing superpositions to collapse). Therefore, the experiment teleported
the quantum state without measuring it.
The ions were teleported inside a NIST-developed multi-zone trap,
first described in 2002. Lasers are used to manipulate the ion's spin and
motion, and to entangle the ions by linking their internal spin states to
their external motion. A key technical advance reported in the current paper
is the capability to entangle ions and then separate them in the trap
(maintaining entanglement) without generating much heat. This previously led
to uncontrolled motions that interfered with operations and required
additional cooling operations. The advance was enabled in part by the use of
smaller electrodes to generate electric fields that move the ions between
The research was supported in part by the Advanced Research and
Development Activity and the National Security Agency.
More information about NIST research on quantum computing can be found
at [Only registered users see links. ].
A non-regulatory agency of the U.S. Department of Commerce, NIST
develops and promotes measurement, standards, and technology to enhance
productivity, facilitate trade and improve the quality of life.
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