Benchmarks for Quantum Circuits of Tungga Electrons
A new methodology for abstract and universal descriptions of quantum circuit fidelity.
Manipulating individual electrons with the aim of using quantum effects offers new possibilities and greater precision in electronics. However, this single electron circuit is governed by the laws of quantum mechanics, which means that deviations from error-free operation still occur – although (in best-case scenarios) it is extremely rare. Thus, insights into the physical origins and metrology aspects of this fundamental uncertainty are critical to the further development of quantum circuits. To this end, scientists from the Physikalisch-Technische Bundesanstalt (PTB) and the University of Latvia have teamed up to develop a statistical testing methodology. The results have been published in the journal Nature Communications.
Single electron circuits are already used as quantum standards of electric current and in prototype quantum computers. In these miniature quantum circuits, interaction and noise hinder the investigation of fundamental uncertainties and measuring them is a challenge, even for the metrology accuracy of the measuring equipment.
In the field of quantum computers, testing procedures also referred to as “benchmarks” are often used where the principle of operation and accuracy of the entire circuit are evaluated through the accumulation of errors following the sequence of operations. Based on this principle, researchers from PTB and the University of Latvia have now developed a benchmark for single electron circuits. Here, circuit fidelity is explained by random steps of the error signal recorded by the integrated sensor when the circuit repeatedly performs operations. Statistical analysis of these “random journeys” can be used to identify rare but unavoidable errors when individual quantum particles are manipulated.
Through this “random walking benchmark”, individual electron transfers are investigated in a series consisting of a single electron pump developed in PTB as the main standard for realizing ampere, the basic unit of SI. In this experiment, sensitive detectors recorded fault signals with a single electron resolution. Statistical analysis made possible by calculating individual particles not only shows the fundamental limitations of circuit fidelity caused by external interference and temporal correlation, but also provides a powerful measure for assessing errors in applied quantum metrology.
The methodology developed within the scope of this work provides a rigorous mathematical basis for validating quantum standards of electrical quantity and opening new pathways for the development of integrated complex quantum systems.