Benchmark for single-electron quantum circuits

Top: Counting statistics (ptx) of an error signal (x) recorded by a single-charge detector, shown as a function of the number of repetitions (t) of the transfer operation; these repetitions were performed by the single-electron circuit. Bottom: Simulation of the underlying “random walks” (blue lines) based on this measurement signal. Here, the width of the line shows how frequently a step takes place. The red line exemplifies a single path of the error signal. Credit: Ubbelohde

Scientists from the Physikalisch-Technische Bundesanstalt (PTB) and the University of Latvia have collaborated to develop a statistical testing methodology of the physical origin and the metrological aspects of the fundamental electron uncertainty.

Single-electron circuits are already used as electric-current quantum standards and in quantum-computer prototypes. In these miniaturized quantum circuits, interactions and noise impede the investigation of the fundamental uncertainties and measuring them is a challenge, even for the metrological precision of the measurement apparatus.

The team described the circuit’s fidelity by the random steps of an error signal recorded by an integrated sensor while the circuit repeatedly executes an operation. The statistical analysis of this “random walk” can be used to identify the rare but unavoidable errors when individual quantum particles are manipulated.

By means of this “random-walk benchmark”, the transfer of individual electrons was investigated in a circuit consisting of single-electron pumps developed at PTB as primary standards for realizing the ampere, an SI base unit. In this experiment, sensitive detectors record the error signal with single-electron resolution. The statistical analysis made possible by counting individual particles not only shows fundamental limitations of the circuit’s fidelity induced by external noise and temporal correlations but also provides a robust measure of assessing errors in applied quantum metrology. (SciTechDaily)

Their results have been published in the journal Nature Communications.

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