Processing Quantum Signals Carried by Electrical Currents

PRXQuantum.2.020314

A team of French and Dutch researchers present a general signal processing method for processing, analysing and representing electrical quantum currents directly at the level of individual electronic wave functions.

Quantum mechanics and the associated interference effects govern the laws of electricity of small conductors at low temperatures. It is responsible for its unusual properties such as deviations from the standard law of impedance composition. As spectacular as these effects may be, this image of electronic transport is still very close to the classical description of wave optics that had emerged from the 19th century.

Nevertheless, quantum electronics has recently entered a new era that cannot be grasped by any classical wave equation paradigm. Recently developed fast electron emitters generate quantum electrical currents carrying one to few elementary excitations per period, thereby bringing electronics closer to the paradigm of quantum optics, which aims at manipulating single to few photon states of the quantum electromagnetic field. In electron quantum optics, several tomography protocols have recently been demonstrated, probing the single-particle content of time-dependent quantum electrical currents. These breakthroughs offer new possibilities such as encoding classical or quantum information with electrons, engineering quantum circuits to simulate complex many-body problems and probing them with single to few particle excitations, or developing electronic sensors, exploiting the extreme sensitivity of quantum electrical currents to the electromagnetic field. However, despite rapid progress, this field still lacks a toolbox for processing, analyzing, and representing the quantum information embedded in quantum electrical currents.

In this paper, authors present a general algorithm for extracting the single-particle wave functions present within a time-periodic quantum electrical current, their emission probabilities, and mutual coherence and apply it to the analysis of several electron sources. This work establishes the grounds for the development of signal processing of quantum electrical currents, directly at the level of electronic wave functions, a key step in the development of electron-based quantum technologies.

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This work is published in Physical Review X: https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.2.020314