After the First World War Einstein made contributions to the development of quantum theory, including Bose-Einstein statistics and the basics of stimulated emission of radiation from atoms (which was later used to develop lasers). He gave the nod of approval that led to the rapid acceptance of Louis de Broglie’s ideas about matter waves but he never came to terms with the Copenhagen interpretation of quantum mechanics. The Copenhagen has become the more popular and standard interpretation.
According to the Heisenberg Principle, the moment at which a measurement takes place is the moment at which the randomness lying at the heart of quantum reality expresses itself. Up to that point, everything is fine. Amplitudes change in a completely predictable, and more importantly, calculable way. The observer changes the state of what is being observed. Outcomes can be predicted according to governing probabilities, but the actual outcome cannot be known in advance.
This was something Einstein could not live with. Einstein, as a determinist, felt that the world is a structured and rigid web where effects follows cause and all things should be predictable, given the right information. Einstein acknowledged that quantum theory works but he did not like the philosophy behind it. If whether or not, for example, Niels Bohr, Einstein’s quantum physics counterpart, were to throw a book across the room Einstein would be able to predict the outcome of Bohr’s “choice.” Einstein would of course say that choice is the wrong word to use; rather, the brain is a complex machine with cogs whirring round to produce a predictable action. The basis of Einstein’s view was a philosophical conviction that the world did not include random events: an objection summed up in Einstein’s widely quoted saying, “God does not play dice.” Bohr is reported to have responded to Einstein with the witty reply, “Don’t tell God what to do.”
Strict [or hard] determinism may be the only way to avoid the implication from quantum mechanics and experiments such as the delayed choice experiment. This experiment suggests that quantum communications occur instantaneously across any distance, or even travel backwards in time. The determinist is not yet defeated, quantum mechanics comes with a state of collapse and that seems to be linked to measurement. Whatever measurements are, they are very specific situations and probably linked to what happens when a particle bumps into a measuring device.
Einstein played a prominent role in the early development of quantum mechanics, particular in his philosophical approach to it. How one interprets quantum mechanics will shape the answer to the question of determinism and free will. Empirical testing does not seem to be enough to provide a satisfactory answer; rather, it how the data is interpreted. Einstein’s approach to the rejection of genuine random events has been an influence of the contemporary debate. It has been argued that Einstein’s determinism is correct, but it may be a mistake for him to base it on random events. Randomness is not sufficient for determinism to be true; a lack of causality would be sufficient. Even with the delayed choice experiment there seems to be a lack of causality, if anything it would be backwards causality. The free will proponent must be careful not to appeal to any ignorance for a lack of explanation of such quantum events. Einstein’s reason for determinism (randomness) does nothing to advance his case. If anything, quantum experiments such as the delayed choice experiment only show that there is randomness in the world, not that there is purposeful, free agency. All quantum mechanics entails is that there are random events in the brain (or whatever) that yield unpredictable behavior, which the agent is not responsible. Thus, it seems to be the case that Einstein’s philosophy of determinism has persevered.
 Kenneth William Ford, The Quantum World: Quantum Physics for Everyone (Cambridge, MA: Harvard University Press, 2004), 117.
 At this time there are at least ten regularly cited interpretations of quantum physics varying in interpretation of wave collapse, determinacy/indeterminacy, superpositions, and Schrödinger’s equations.
 The equation: (change in x multiplied by the change in px is greater than or equal to half of Planck’s constant). For a given state, the smaller the range of probable x values involved in a position expansion, the larger the range of probable px values involved in a momentum expansion, and vice versa. The key to the expression is the greater than or equal to because it places a limit on how precise the two measurements can be. The principle is relating and for the same state ( signifies change, h, h-bar, is the Planck constant). Heisenberg’s target was causality. The Copenhagen interpretation adopted this principle. Jonathan Allday, Quantum Reality: Theory and Philosophy (Boca Raton, FL: CRC Press, 2009), 247-248.
 Jonathan Allday, Quantum Reality: Theory and Philosophy (Boca Raton, FL: CRC Press, 2009), 100-101.
 If photons are fired through the experiment one at a time (firing photons at a wall with two holes and a photon detector on the other side of the holes), they will build up an interference patter on the other side, as if they had gone through both holes at once and interfered with themselves. If the experiment is set up so that detectors monitor which hole the photo goes through, the photon is indeed observed to be going through only one hole, and there is no interference pattern. If a detector is set up not at the holes but intermediate between the two holes and the back wall detector screen then it may be possible to see which route a particular photon took after it had passed the two holes before it arrived at the screen. Quantum theory says that if we choose to turn this new detector off and not look at the photons, they will form an interference pattern. But if we look at the photons to see which hole they went through, even if we look after they have gone through the hole, there will be no interference pattern. The delayed choice comes into the story because we can make the decision whether or not too look at the photon after the photon has already passed through the hole[s]. The decision made seems to determine how the photon behaved at the time it was passing though the hole a tiny fraction of a second in the past. It seems as though the photons have some precognition about how the set-up of the experiment will be before it sets out on its journey. This has also provided credence to the metaphysical concept of backwards causation. John R. Gribbin, Mary Gribbin, and Jonathan Gribbin (Q Is for Quantum: Particle Physics from A-Z. London: Weidenfeld & Nicolson, 1998), 102-103.
 This is most notably accepted by the transactional interpretation of quantum mechanics. Gribbin, 104.
 Predictability may be equivalent to randomness, not a lack of causality. Louis Pojman, Philosophy: The Pursuit of Wisdom (Boston, MA: Wadsworth, 2006), 229-230.
 Recalling Einstein’s epistemic method, he based all of his philosophy and work on the ontological status of the universe. He did not seem to indicate an immateriality to the mind. Einstein’s influence is limited only to the physical aspect for the substance dualist. Here is where the substance dualist and the scientific theologian must resume the dialogue.