Albert Einstein's point of view on Quantum Electrodynamics (QED) evolved over time, and he had several concerns and criticisms about the theory. However, it's important to note that Einstein was not directly involved in the development of QED, which primarily took place in the mid-20th century with contributions from Richard Feynman, Julian Schwinger, and Sin-Itiro Tomonaga.
Einstein's main objection to QED stemmed from its probabilistic nature. He famously remarked, "God does not play dice with the universe," expressing his discomfort with the inherent randomness and uncertainty in quantum theory. This sentiment reflected his preference for a deterministic view of physics, where precise predictions could be made without relying on probabilities.
Another aspect of QED that troubled Einstein was the notion of action-at-a-distance. Quantum mechanics, including QED, allows for the possibility of entanglement, where particles can instantaneously influence each other's states regardless of the distance between them. Einstein was skeptical of this concept and referred to it as "spooky action at a distance." He sought a more local and deterministic explanation for physical phenomena.
Despite his reservations about QED, it is worth noting that Einstein recognized the theory's remarkable success in explaining and predicting phenomena at the microscopic scale. QED has been highly successful in describing the behavior of electromagnetic interactions, and its predictions have been extensively confirmed by experiments.
In summary, Einstein had concerns about the probabilistic nature of QED and its reliance on action-at-a-distance phenomena. However, his objections did not undermine the validity and success of the theory in describing the behavior of electromagnetic interactions.