- We have developed an atom-imaging technique that allows us to detect the
positions of individual Rydberg atoms, which are atoms with a highly
excited outer electron. Using this technique, we provide the first
spatially resolved images that demonstrate the “Rydberg blockade.” This
effect is at the core of proposals for a quantum computer architecture
based on neutral atoms
A Rydberg atom has such a tenuous grasp on its excited electron that the
atom is extremely sensitive to external electric and magnetic fields,
and interacts very strongly with other Rydberg atoms. The interaction
between Rydberg atoms is so strong that a Rydberg atom can “block” the
laser-excitation of another Rydberg atom by shifting the energy levels
of the second atom out of resonance with the laser. This is termed the
Rydberg blockade effect. This process leads to quantum entanglement,
which can be used in quantum computation algorithms.
A second Rydberg atom can only be excited if it is farther than a
“blockade radius” from the first atom. We directly measured this
blockade by laser-exciting Rydberg atoms in a cold atomic vapor and
measuring the Rydberg atom positions. We observe a blockade radius of
about 10 microns, which is about 100,000 times larger than the radius of
a ground state atom.
