Two of the best known concepts in quantum mechanics are the Heisenberg uncertainty principle and Schrodinger's cat. In new age hippy pop culture, these are the two clichés you can expect to see in any discussion about quantum mechanics and Buddhism. These concepts are sometimes invoked to suggest that the universe can be magically manipulated by the mind of an observer.
It's important to know, though, that the degree of uncertainty for everyday particles and objects is very small, leaving us with a universe that behaves classically on a macroscopic, human level. Even the very practical concept of electron delocalization is not going to register with our senses (except, maybe, for the sense of smell). Sure, an electron has a non-zero probability of "appearing" very far away from its home nucleus, but the odds are so low, and the electron so tiny, and the distances constituting "very far" are still so small, that it's not going to make a difference in your everyday life (beyond the noteworthy application of certain electronics, which make important use of this phenomenon). It's definitely not going to help you levitate or walk through a wall. So for the most part we're stuck with the plain old reality we already knew we had, and our desire for scientifically-grounded telepathy remains wishful thinking.
However, the definition of an observer has been clarified since Schrodinger's time. An observer is no longer defined as a human being, who, granted the magic power of consciousness, has an exclusive ability to collapse wavefunctions everywhere he looks. Instead, an "observer" is any classical system that interacts with a quantum system, whether or not a measurement is made or a human ever sees it. In other words, when a large object interacts with a tiny, quantized system like an atom or a photon, the quantum system shows its classical side and acts like it has only one state instead of a superposition of many. This means we can safely forget about Schrodinger's cat because (someone should have thought of this a long time ago) the paradox is resolved by recognizing that the cat is the observer that collapses the wavefunction. (Actually it's the apparatus that releases the poison, since that's the first classical system to interact with the radioactive, quantized particles, but the cat deserves some recognition.)
It would seem, then, that the new age hippies have botched the spiritual interpretation of quantum mechanics by exaggerating or misinterpreting early concepts of the science. Does that mean the field is totally irrelevant to the quest for enlightenment? Assuming that you already know that enlightenment is to be found within and that any outside information is merely icing on the cake, I'll say no--quantum mechanics is not irrelevant because it encompasses some of the most precise observations ever made about physical reality. It is thus a tool for helping one better look at and understand reality, which in turn helps one act more fully in accordance with reality.
So where are we now?
A major breakthrough in this field came in the mid-20th Century with the development of quantum electrodynamics (QED), one of the most successful scientific theories in history. It is successful because it has stood up to extremely rigorous testing, it has been confirmed to match observation to the 12th decimal place in the case of some predictions, and it has provided a framework for explaining much of real chemistry and optics. It has not received much popular attention though, probably because it is newer, more advanced, and more complicated than the initial incarnations of quantum mechanics, which new age hippies are still, futilely, trying to wrap their minds around.
|... culminating in one reality.|
A related theory, quantum chromodynamics (QCD), explains the behavior of atomic nuclei. With QED and QCD together, atoms and their interactions are thoroughly modeled using this crazy sum over histories approach, which means that all the matter we care about on a daily basis (the matter making up our bodies and environment), and all the energy we care about (the energy of light and chemical bonds), takes form through the interactions of possibilities. Thus, the philosophical implication that emerges from modern physics is that, in a certain sense,
Reality is the sum of all possibilities.
That blows my mind. We're sitting at a crossroad of infinite possibility, not just in space and time, but in every particle and every event and every thing. Thinking about that for a bit, I realize that pop culture depictions of alternate universes and many-world interpretations of quantum mechanics are far, far too narrow to be accurate. There's a lot more out there in the realm of possibility. Moreover, the possibilities are not separate from one another; they're all interfering together: If there are parallel universes in which 9/11 didn't happen (and there certainly are in the "realm" of possibility), they are not separate from our own. Rather, all the microstates of every quantum system that would comprise those possible universes are interfering with the microstates of every other quantum system that comprise possible universes in which 9/11 did happen, and the net result, the grand summation, is the reality we know in which 9/11 happened.
The really crazy implication of this theory is that reality has an intrinsic way of combining all these possibilities into one history, just on its own. Wherever and however these possibilities exist, reality is mashing all of them together and letting them add up through some process that must be fundamental to the nature of reality itself. Wow! Several months ago I explored this idea, in my second post. It reminds me of a statement in the Lankavatara Sutra in which Buddha says, "When this entire universe is regarded as concatenation and as nothing else but concatenation, then the mind, by its patient acceptance of the truth that all things are un-born, gains tranquility."
On that note, I suggest that you don't try to figure out what this "really means," because it's too big to figure out. Instead, the next time you have a moment to yourself, just look around, notice what it feels like to be you, and consider that This Is It. This is, in one sense, everything trying to happen at once. You might find some tranquility by considering that, maybe, it absolutely has to be this way.