  Fourier transform spectroscopy with classical interferometry corresponds to
the measurement of a single-photon intensity spectrum from the viewpoint of the
particle nature of light. In contrast, the Fourier transform of two-photon
quantum interference patterns provides the intensity spectrum of the two
photons as a function of the sum or difference frequency of the constituent
photons. This unique feature of quantum interferometric spectroscopy offers a
different type of spectral information from the classical measurement and may
prove useful for nonlinear spectroscopy with two-photon emission. Here, we
report the first experimental demonstration of two-photon quantum interference
of photon pairs emitted via biexcitons in the semiconductor CuCl. Besides
applying Fourier transform to quantum interference patterns, we reconstruct the
intensity spectrum of the biexciton luminescence in the two-photon sum or
difference frequency. We discuss the connection between the reconstructed
spectra and exciton states in CuCl as well as the capability of quantum
interferometry in solid-state spectroscopy.
