Final answer:
Einstein's most quoted remark on quantum mechanics is "God does not play dice with the universe," reflecting his discomfort with its non-deterministic nature.
Step-by-step explanation:
Albert Einstein's most quoted quote about quantum mechanics is likely his expression of discomfort with the theory's inherent randomness: "God does not play dice with the universe." While Einstein contributed significantly to the foundations of quantum mechanics, winning the Nobel Prize in 1921 for his explanation of the photoelectric effect, which was one of the seminal pieces of evidence for quantum theory, he struggled with some of its implications. Einstein's work proposed photons as quanta of electromagnetic radiation and explained the photoelectric effect, but the nondeterministic nature of quantum mechanics later uncovered by Werner Heisenberg's uncertainty principle and Erwin Schrödinger's wave function portrayed a universe far less predictable than Einstein was willing to accept.
Einstein's discomfort with quantum mechanics peaked with the concept that it is impossible to know both the position and velocity of a particle, such as an electron, at the same time - a stark contrast to the deterministic predictions of classical mechanics. Despite his reservations, the work of Einstein and his contemporaries laid essential groundwork for the theory of quantum mechanics, which remains a central pillar of modern physics.