Portrait of a Photon

Aleksei Sharafiev, Mathieu L. Juan, Oscar Gargiulo +4 more

At the dawn of Quantum Physics, Wigner and Weisskopf obtained a full analytical description (a photon portrait ) of the emission of a single photon by a two-level system, using the basis of frequency modes (Weisskopf and Wigner, "Zeitschrift für Physik", 63, 1930). A direct experimental reconstruction of this portrait demands an accurate measurement of a time resolved fluorescence spectrum, with high sensitivity to the off-resonant frequencies and ultrafast dynamics describing the photon creation. In this work we demonstrate such an experimental technique in a superconducting waveguide Quantum Electrodynamics (wQED) platform, using single transmon qubit and two coupled transmon qubits as quantum emitters. In both scenarios, the photon portraits agree quantitatively with the predictions of the input-output theory and qualitatively with Wigner-Weisskopf theory. We believe that our technique allows not only for interesting visualization of fundamental principles, but may serve as a tool, e.g. to realize multi-dimensional spectroscopy in waveguide Quantum Electrodynamics.

Myron Wyn Evans, Jean Pierre Vigier, Sisir Roy +1 more

Sergey N. Filippov, Vladimir I. Man’ko

Ya. A. Korennoy

Non-redundant and normalized four-component vector tomographic portrait fully describing the states of spin 1/2 quantum particles was introduced. Dequantizer and quantizer for such portrait were found, and generalization to the case of spin (2^N-1)/2 was done (N is a natural number). It was shown that such a portrait is completely defined by a thriple of non-complanar vectors with the lengthes equal or less then unity. A clear geometric interpretation of the choice of parameters for finding normalized dequantizers and quantizers is presented and numerical examples of such dequantizers and quantizers for spin 1/2 are given.