You may be thinking of the quantum "observer effect." But that doesn't say observers don't exist - on the contrary, it assumes the existence of observers. It is about how the act of observing has an effect on the system being observed - e.g. to see, your eye absorbs photons which are transformed during that process.
There's also the somewhat related "measurement problem." This one calls into question what it means to be an observer, so that may be what you're really thinking of.
The measurement problem is about how a quantum system changes from being in a state of superposition with no single defined state, to having a single state. In some quantum interpretations, this is considered to be a consequence of "observation" or "measurement," but that only raises the question of what it means to measure or observe something.
This does not, in and of itself, mean "there is no you." In fact it's the opposite in some interpretations, the existence of observers is assumed. The conclusion that "there is no you" requires imposing an additional philosophical perspective.
There's also the somewhat related "measurement problem." This one calls into question what it means to be an observer, so that may be what you're really thinking of.
The measurement problem is about how a quantum system changes from being in a state of superposition with no single defined state, to having a single state. In some quantum interpretations, this is considered to be a consequence of "observation" or "measurement," but that only raises the question of what it means to measure or observe something.
This does not, in and of itself, mean "there is no you." In fact it's the opposite in some interpretations, the existence of observers is assumed. The conclusion that "there is no you" requires imposing an additional philosophical perspective.