Superradiant States in Semiconductor Heterostructures: Displaced Fock States or Coherent-States Superpositions?

We study the quantum properties of superradiant (SR) states generated in semiconductor heterostructures at room temperature, using time-domain optical homodyne tomography. We demonstrate that the reconstructed Wigner functions of the SR states are very similar to those of displaced Fock states (DFS) | α, n⟩ with different α and n. The statistics of photons of the SR states are fitted well by that of DFS with dissipation. The estimated purity of the reconstructed states is in the range of 0.91 – 0.94. In addition, the reconstructed SR Wigner functions exhibit oscillating features of their positive parts. Those wavy structures look very similar to oscillating parts of Wigner functions of some superpositions of two coherent states. Similarities and differences between SR states, DFS, and coherent-state superpositions are discussed.