Experimental test of environment-assisted invariance

Symmetries play a central role in physics with widereaching implications in fields as diverse as spectroscopy and particle physics. It is therefore of fundamental importance to identify and understand new symmetries of nature. One of these more recently identified symmetries in quantum mechanics has been named environment-assisted invariance, orenvariance[1].Itapplies in certain cases where acomposite quantum object consists of a system part, labeled S, and an environment part, labeled E. If some action is applied to the system part only, described by some unitary transformation US, then the state is said to be envariant under US if another unitary applied to the environment UE can restore the initial state. This can be expressed,