Josephson received the 1973 Nobel Prize in Physics for discovery
of the Josephson effect, which occurs in two superconducting
layers separated by an insulating oxide. Under certain
conditions current can pass through the insulator through
tunneling of Cooper pairs of electrons. The effect has been used
to design superconducting quantum interference devices (SQUID)
because switching is very fast, in the order of picoseconds.
Tunneling in the Josephson junctions is very sensitive to
magnetic fields and can therefore be used to measure extremely
small magnetic fields with thresholds as low as Tesla. Josephson
junctions are also used for other precision measurements. The
standard volt is now defined as the voltage required to produce
a frequency of 483,597.9 GHz in a Josephson junction oscillator.
A schematic diagram of a circuit with a Josephson junction is
shown below. The quantum effects can be modeled by the
Schrodinger equation, but it turns out that the circuit can also
be modeled as a system with lumped pa