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Quantum Information Research at NIST: Goals and Vision |
Engineering Secrets: How to Entangle Ions
The teleportation
of atomic states—an automated process requiring 4 milliseconds
in current experiments—is an outcome of many NIST achievements
in ion-trapping hardware engineering. A trapped beryllium ion is about
10 nanometers (billionths of meter) in diameter. NIST physicists designed
an electromagnetic apparatus smaller than a penny that traps a number
of ions within an area smaller than a grain of rice. Tiny electrodes
are used to move ions between zones so they can be manipulated, either
individually or in sets of two or three, with ultraviolet laser beams.
Environmental conditions such as electronic
“noise” are precisely controlled to avoid unintended atom
motions. NIST physicists developed a procedure for entangling ions in
a controllable way. Two laser beams are positioned at right angles to
apply an oscillating force to a pair of ions. The lasers are tuned so
the difference between their frequencies is very close to the frequency
of the ions’ natural vibrational motion. If both ions are in the
same spin state, the lasers have no effect. If the ions are in different
spin states, they feel an opposing laser force that causes the ions to
stretch apart. If the ions are in superpositions, the stretching motion
reflects a condition of being excited and not excited at the same time.
This coupling of spin states with stretching motions has the effect of
entangling the two ions in a controlled way. |
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Date
created: 4-11-06
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