The purpose of this paper is to investigate the two-capacitor paradox using circuit models developed in the analysis of circuits that include nanoelectronic single-electron tunneling devices. The two-capacitor paradox, in which it seems that energy is not conserved in a simple circuit consisting of two capacitors in parallel separated by an ideal switch, is resolved by applying linear circuit theory utilizing a current—described by a (Dirac) delta function—and stepping voltages across all three elements. Based on a similar description, successfully used for tunneling of electrons through metal junctions in nanoelectronics, the switch is modeled as a device across which—upon closing—the voltage steps down while the current through it is an impulse. The model distinguishes three intervals in describing the ideal switch: t < 0, t = 0, and t > 0. As a consequence, the ideal switch dissipates energy during the switching action at t = 0 in zero time. Although the solution of the two-capacitor problem looks like a theoretical curiosity, the application of nanoelectronic concepts allow a physical explanation based on electron tunneling; it shows that the ideal switch is best described by the tunneling of many electrons. In such a context, some of those electrons loose energy and the v-i characteristic shows Ohm’s law.@en

The purpose of this paper is to review and derive circuit models to support the synthesis of circuits and systems to be used for reading out devices based on quantum technology. In quantum technology, reading out devices is difficult; measuring may destroy the information stored in the quantum system. Optimal design can be achieved by signal processing circuits based on the nullor that, theoretically, do not extract power and thus energy from the system. Because of the nullator properties at the input of the nullor two-port and the norator properties of the output of the nullor, signals can be tapped from the quantum system without absorbing power from it; energy to do so is provided by external sources. Circuits based on the nullor are theoretically circuits for reading out signals from devices in quantumtimal circuits for reading out signals from devices in quantum systems and for processing this data afterwards. In the paper, basic sensing circuit concepts based on the nullor and their descriptions based on the chain-matrix (K-matrix) are presented. Some possible candidates for implementing the theoretical schemes are discussed, and as a possible application, a single-electron tunneling electrometer is described.@en