Quantum tomography of electrical currents
In quantum nanoelectronics, time-dependent electrical currents are built from few elementary excitations emitted with well-defined wavefunctions. However, despite the realizations of sources generating quantized numbers of excitations, and despite the development of the theoretical framework of time-dependent quantum electronics, extracting electron and hole wavefunctions from electrical currents has so far been out of reach, both at the theoretical and experimental levels. In this work, by combining two-particle interferometry with signal processing, we demonstrate a quantum tomography protocol able of extracting the generated electron and hole wavefunctions and their emission probabilities from any electrical current. Using our technique, we extract the wavefunctions generated by trains of Lorentzian pulses carrying one or two electrons. By demonstrating the synthesis and complete characterization of electronic wavefunctions in conductors, this work offers new perspectives for quantum information processing with electrical currents and for investigating basic quantum physics in many-body systems.