Dicke superradiance as a nondestructive probe for quantum quenches in optical lattices

Abstract

We study Dicke superradiance as collective and coherent absorption and (time-delayed) emission of photons from an ensemble of ultracold atoms in an optical lattice. Since this process depends on the coherence properties of the atoms (e.g., superfluidity), it can be used as a probe for their quantum state. In analogy to pump-probe spectroscopy in solid-state physics, this detection method facilitates the investigation of nonequilibrium phenomena and is less invasive than time-of-flight experiments or direct (projective) measurements of the atom number (or parity) per lattice site, which both destroy properties of the quantum state such as phase coherence.

Dicke superradiance as nondestructive probe for the state of atoms in optical lattices

“…Inserting back into the operatorial part (11), and contracting the sums according to µ = ν and η = ρ, the result can be written as an absolute square [41] …”

“…The case of a bosonic lattice was already studied in reference [41], where we came to the conclusion that the superradiance peak does not decay after an adiabatic transition, i.e., the superradiant emission probability reads P = N 2 δ κinκout P single . For a detailed derivation of this result, see Appendix H.…”

“…The emission probability after the adiabatic transition can be calculated analog to (41). As a shortcut, the state (106) can be understood as exciton creation applied to the superfluid ground state, i.e., the emission probability can be evaluated viâ …”

“…Partial condensation state Therefore we regarded a more general state in reference [41] which contains a certain number N 1 of bosons in the ground state at k = 0 while the other N 2 bosons should be equally distributed between all k-modes. Such a state could, for example, represent a simple toy model for a thermal state with partial condensation.…”

“…In this paper, we extend the probing scheme first presented in [41] to a general formalism, placing special emphasis on the difference between bosonic and fermionic systems. We describe in detail an alternative, nondestructive detection method which is based on Dicke superradiance, i.e., the collective and coherent absorption and (time delayed) emission of photons from an ensemble of ultracold atoms [42][43][44][45][46].…”