We reconstruct the polarization-entangled state of individual frequency components of the biphoton wave function by stimulated emission tomography. The frequency-resolved polarization state enables new insight into frequency-polarization correlations of the quantum process.
We perform a multidimensional characterization of a polarization-entangled photon-pair source using stimulated emission tomography (SET). We measure the frequency-resolved polarization density matrix, which is composed of thousands of individual polarization density matrices, each corresponding to a different frequency pair. The measurement exhibits detailed information about correlations that would be difficult to observe using traditional quantum state tomography. This demonstration exhibits the power of SET to characterize a source of quantum states with multi-dimensional correlations and hyper-entanglement. The SET technique can be applied to a variety of photon-pair-based sources for the optimization and engineering of quantum states.
In this work, we demonstrate the use of stimulated emission tomography to characterize a hyperentangled state generated by spontaneous parametric downconversion in a cw-pumped source. In particular, we consider the generation of hyperentangled states consisting of photon pairs entangled in polarization and path. These results extend the capability of stimulated emission tomography beyond the polarization degree of freedom and demonstrate the use of this technique to study states in higher dimension Hilbert spaces.
We demonstrate a technique of quantum-state tomography for measuring the complex temporal wave function of narrowband biphotons with polarization-dependent and time-resolved two-photon interference. While the amplitude function of the biphoton waveform is directly related to the second-order correlation function which is determined by the two-photon coincidence measurement, the phase function is retrieved from six sets of time-resolved two-photon interference measurements projected onto different polarization subspaces. We apply this technique to experimentally reconstruct the temporal quantum states of the narrow-band biphotons generated from the spontaneous four-wave mixing in cold atoms. As compared with the homodyne detection, our method doesn't require any external phase reference.