Quantum-referenced spontaneous emission tomography

We present a method of tomography in which photon pairs from a device-under-test (DUT) are experimentally characterised by quantum interference with a reference photon pair source; we call this quantum-referenced spontaneous emission tomography (Q-SpET). In Q-SpET, the joint spectral phase (JSP) of photon pairs generated by a DUT can be reconstructed by combining four spectrally resolved interferograms. We demonstrate this theoretically and experimentally, characterising the JSP of a microresonator photon pair source. Our method is fully implemented on a chip, demonstrating the compactness, inherent phase stability, low complexity, and resource efficiency of this method.