  The field of metamaterial research revolves around the idea of creating
artificial media that interact with light in a way unknown from naturally
occurring materials. This is commonly achieved by creating sub-wavelength
lattices of electronic or plasmonic structures, so-called meta-atoms, that
determine the interaction between light and metamaterial. One of the ultimate
goals for these tailored media is the ability to control their properties
in-situ which has led to a whole new branch of tunable and switchable
metamaterials. Many of the present realizations rely on introducing
microelectromechanical actuators or semiconductor elements into their meta-atom
structures. Here we show that superconducting quantum interference devices
(SQUIDs) can be used as fast, intrinsically switchable meta-atoms. We found
that their intrinsic nonlinearity leads to simultaneously stable dynamic
states, each of which is associated with a different value and sign of the
magnetic susceptibility in the microwave domain. Moreover, we demonstrate that
it is possible to switch between these states by applying a nanosecond long
pulse in addition to the microwave probe signal. Apart from potential
applications such as, for example, an all-optical metamaterial switch, these
results suggest that multi-stability, which is a common feature in many
nonlinear systems, can be utilized to create new types of meta-atoms.
