rated by about 1 m. At the start of the
process, the investigators initialized each
ion using a microsecond-long pulse of
369.5-nm light from a frequency-doubled
amplified diode laser. They applied a resonant microwave burst of a controlled
phase and duration to put the first ion in
the qubit state to be teleported to the second ion.
They then fired a picosecond-long laser
pulse at both ions. Each ion emitted a single photon correlated to the originating
atom’s qubit state. After capturing the
emitted photons and routing them through
a 50/50 beamsplitter, they recorded their
arrival at one or both of two detectors. The
latter case signaled when the two atoms
were entangled, with their properties inter-
twined. When that happened, the researchers measured the qubit state of the
first ion, which provided them the ability
to recover information from the second
ion that had been stored in the first.
Given the entanglement signal, the
method faithfully teleports information
with 90 percent accuracy, the group reported in the January 23 issue of Science.
A drawback is that the entanglement signal occurred only a little more than twice
every hundred million attempts. The researchers overcame this low probability by
repeating the entire procedure tens of
thousands of times per second. Even with
that, entanglement was detected only
every 12 minutes.
In scaling up to a larger number of
atomic nodes, the likelihood of detecting
entanglement must be increased, and
Monroe said the group is working on this.
“We have some ideas [about] how to add
several orders of magnitude to the success
probability of getting those photons into
fibers and detected.”