  In a standard Josephson junction the current is zero when the phase
difference between the superconducting leads is zero. This condition is
protected by parity and time-reversal symmetries. However, the combined
presence of spin-orbit coupling and magnetic field breaks these symmetries and
can lead to a finite supercurrent even when the phase difference is zero. This
is the so called anomalous Josephson effect -- the hallmark effect of
superconducting spintronics --and can be characterized by the corresponding
anomalous phase shift ($\phi_0$). We report the observation of a tunable
anomalous Josephson effect in InAs/Al Josephson junctions measured via a
superconducting quantum interference device (SQUID). By gate controlling the
density of InAs we are able to tune the spin-orbit coupling of the Josephson
junction by more than one order of magnitude. This gives us the ability to tune
$\phi_0$, and opens several new opportunities for superconducting spintronics,
and new possibilities for realizing and characterizing topological
superconductivity.
