Quantum optics using atomic arrays (Prof. Dr. Darrick Chang)

Date:
Oct 23, 2018

Time:
14:30  15:00

Speaker:
Prof. Dr. Darrick Chang

ICFO – The Institute of Photonic Sciences, Barcelona, Spain

Location:
MaxPlanckInstitut für Quantenoptik

Room:
Hörsaal, Raum B 0.32 / New lecture hall, Room B 0.32

Host:
MPQ, Laser Spectroscopy Division
Ensembles of atoms or other quantum emitters are envisioned to be an important component of quantum applications, ranging from quantum memories for light to photonphoton gates to metrology. It has historically been an outstanding challenge to exactly solve for the quantum dynamics of an optical field as it propagates through and interacts with an ensemble. The standard axiomatic approach is to use the onedimensional MaxwellBloch equations, which assume that excited atoms emit independently into unwanted directions. This ignores the wave interference of the emitted light, which depends on correlations between the atoms.
Here, we discuss an alternative theoretical approach, which accounts for
interference and the precise atomic positions. In this formalism, an
interacting quantum spin model describes the dynamics of the atomic internal
degrees of freedom under multiple photon scattering, while the field properties
can subsequently be reconstructed from the spin correlations. Using this
model, we then show how interference can be exploited as an extremely powerful
resource to suppress the unwanted emission of light and the subsequent loss of
information into undesirable directions. The effects of interference are
particularly prominent in ordered arrays of emitters. As two specific examples,
we construct a new protocol for a quantum memory for light based upon an
ordered array, whose error rate as a function of system resources scales
exponentially better than previously known bounds. We also show the
interrogation time in an optical lattice clock can be significantly extended,
through the excitation of collective subradiant atomic states whose spontaneous
emission rates are strongly suppressed.