Long-lived spin squeezing and quantum phase magnification in a trapped-atom clock with fiber Fabry-Perot cavity
Prof. Dr. Jakob Reichel (Laboratoire Kastler Brossel, ENS Paris, France)

Many if not all future quantum technologies are enabled by quantum
correlations in a well-controlled many-particle system. In ensembles
of atoms, ions and many other quantum emitters, such correlations can
be generated with a high-finesse optical cavity. This approach is
particularly promising for quantum metrology. I will present an
experiment combining a compact trapped-atom clock on an atom chip and
a fiber Fabry-Perot microcavity. This first "metrology-grade" spin
squeezing experiment enabled us to produce spin squeezed states with
unprecedented lifetime up to a second, and to observe a "quantum phase
magnification" effect due to the subtle interplay of these
many-particle entangled states with the exchange interaction that
occurs in the trapped low-temperature gas.