“While physicists have debated about the nature of the quantum state since the early days of quantum theory (with, most famously, Bohr being in favor of the ontic interpretation and Einstein arguing for the epistemic one), most modern evidence has supported the view that the quantum state does indeed represent reality.
Philosophically, this interpretation can be hard to swallow, as it means that the many counterintuitive features of quantum theory are properties of reality, and not due to limitations of theory. One of the most notable of these features is superposition. Before a quantum object is measured, quantum theory says that the object simultaneously exists in more than one state, each with a particular probability. If these states are ontic, it means that a particle really does occupy two states at once, not merely that it appears that way due to our limited ability to prepare particles, as in the epistemic view…”