  Back-action refers to a response that retro-acts on a system to tailor its
properties with respect to an external stimulus. This self-induced effect
generally belongs to both the natural and technological realm, ranging from
neural networks to optics and electronic circuitry. In electronics, back-action
mechanisms are at the heart of many classes of devices such as amplifiers,
oscillators, and sensors. Here, we demonstrate that back-action can be
successfully exploited to achieve $\textit{non-reciprocal}$ transport in
superconducting circuits. Our device realizes a supercurrent diode, since the
dissipationless current flows in one direction whereas dissipative transport
occurs in the opposite direction. Supercurrent diodes presented so far rely on
magnetic elements or vortices to mediate charge transport or external magnetic
fields to break time-reversal symmetry. In our implementation, back-action
solely turns a conventional reciprocal superconducting weak link with no
asymmetry between the current bias directions into a diode, where the critical
current amplitude depends on the bias sign. The self-interaction of the
supercurrent with the device stems from the gate tunability of the critical
current, which uniquely promotes up to $\sim$88% of magnetic field-free signal
rectification and diode functionality with selectable polarity. The concept we
introduce is very general and can be applied directly to a large variety of
devices, thereby opening novel functionalities in superconducting electronics.
