Josephson quantum effect

The Josephson quantum effect is based on quantum mechanics and occurs when a tunnel current flows between two superconductors that are separated by a thin insulating layer. If two superconductors are separated by a (only a few nanometers thin, non-superconducting barrier), Cooper pairs can tunnel from one superconductor through the barrier into the other superconductor. In the static form of the effect (applying a DC voltage), a high-frequency alternating current occurs whose frequency is proportional to the voltage. The dynamic form of the effect (the effect of high-frequency electromagnetic waves), on the other hand, leads to precise frequency-voltage relationships that can be described by equations and allow for an exact method of defining voltage.

In quantum research, the Josephson effect allows for the precise control and measurement of quantum systems by generating quantized voltages and frequencies. This enables (at low temperatures in superconducting quantum circuits) reliable data acquisition and signal processing. So-called Josephson junctions, which are based on this effect, are suitable as quantum bits (qubits) for superconducting quantum computers and serve as the basis for logic operations.

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