Albert Einstein's views on quantum theory were complex and evolved over time. In the early development of quantum theory, Einstein made significant contributions, particularly with his work on the photoelectric effect, which earned him the Nobel Prize in Physics in 1921. However, he was skeptical of certain aspects of quantum mechanics, especially its probabilistic nature and the concept of wave-particle duality.
Einstein's famous quote, "God does not play dice with the universe," reflects his discomfort with the probabilistic interpretation of quantum mechanics. He believed that there must be underlying deterministic laws governing physical phenomena, as opposed to the inherent randomness of quantum theory. This led to his ongoing debate with physicist Niels Bohr and others, known as the Einstein-Bohr debates, where they discussed the philosophical implications of quantum mechanics.
Regarding the reconciliation of quantum theory with his own work in relativity theory, Einstein struggled to find a unified theory that could incorporate both quantum mechanics and general relativity. He dedicated a significant portion of his later years to this pursuit, searching for a theory of everything, also known as a unified field theory, that would encompass both quantum mechanics and gravity.
However, Einstein was unsuccessful in his attempts to develop a unified theory before his death in 1955. It was only later, through the work of other physicists like Richard Feynman, Murray Gell-Mann, and Steven Weinberg, that progress was made in reconciling quantum mechanics and relativity in the framework of quantum field theory and the standard model of particle physics.
In summary, while Einstein made crucial contributions to the development of quantum theory, he remained skeptical of certain aspects of it and sought a unified theory that would encompass both quantum mechanics and his theory of relativity. However, he did not succeed in reconciling the two during his lifetime.