Quantum Mysticism: A Disconnected Connectedness
Can we understand reality by separating it out into little pieces? Conventional wisdom has always pushed back against that notion, for instance in the proverb “No man is an island.” Mystics in all religious traditions push back in a more subtle way, intuiting that the separateness we experience is in large part an illusion. Interestingly, quantum physics reveals a completely new angle on the question. There is such a rich web of quantum connections underlying reality that, were these not hidden, any experience of personal identity and history would not be possible at all.
We normally picture the physical world as a collection of objects which, although interacting with one another, each have their own individual past, present, and future. A central feature of quantum physics, picturesquely called “entanglement,” upends this common-sense picture. Entanglement is not just an idea or an alternate way of seeing the world. For small objects such as atoms, entanglement is both observable and of practical significance, for example serving as an essential resource in quantum computing. However, a sort of dualism emerges from the same quantum laws. Big objects such as people accumulate entanglements so quickly that they always appear to be completely unentangled.
Consider an atom on a collision course with a sharp corner of a wall. We know from the Heisenberg uncertainty principle that the atom cannot have a perfectly well-defined trajectory. So, it will bounce off the corner both to the left and the right — as opposed to picking one direction or the other. We might say that quantum objects surprise us by existing in “both/and” states, in contrast to the “either/or” behavior we normally experience. Although it is strange that a single atom acts this way, we can still describe its state at any moment without reference to anything else. The atom might be taking both paths equally, as in the example above. Or we could have aimed the atom well to the right of the corner, in which case it will take primarily the right path. In either case, there exists an answer to the question: “What is the atom doing at this moment?”
What happens if the atom interacts with another quantum object? Suppose we insert a second atom along the left path such that it is jostled if atom 1 goes that direction. The atoms do not form a molecule or change in any fundamental way — atom 1 just bumps atom 2 if it passes by. After the interaction, the quantum description of the two atoms is a both/and of (A) atom 1 going left with atom 2 jostled, and (B) atom 1 going right with atom 2 unjostled. Does it still make sense to ask the seemingly innocuous question, “What is atom 1 doing after the interaction?” We would have two possible answers: either atom 1 is traveling both paths, or it is traveling only one. It turns out neither of these answers is correct, because how we experience atom 1 depends on how we observe atom 2.
If we perform an either/or measurement of atom 2 — checking to find whether or not it is jostled — then atom 1 will appear to have taken the corresponding single path. If we could only do this type of experiment, it would be easy to mistakenly conclude that atom 1 was now behaving “normally” because the collision obliterated its quantum ability to travel both paths at once. However, if we perform a much more challenging both/and measurement of atom 2 — checking to see if it is in a contradictory state of being simultaneously jostled and unjostled — then atom 1 will show clear evidence of having traveled both paths. This second type of measurement is very difficult, but it has been demonstrated, for example in quantum eraser experiments. We see that any attempt to describe atom 1 by itself can be proven wrong. The atoms have become entangled, and if we are to discuss their status, we must now speak of them in the same breath.
Being yourself composed of atoms, you are also subject to entanglements, and lots of them. Is this entanglement important for your life? Yes, but for a paradoxical reason. Quantum mechanics first presents a serious challenge to the notion of your “normal” existence in a quantum universe. Then entanglement solves that problem, by very effectively suppressing our ability to experience it or other quantum phenomena. This intrinsic feature of quantum mechanics, the self-hiding of entanglement, is called “decoherence”. There are two important effects of decoherence on your everyday life. First, it allows you to experience your own history composed of well-defined facts. As seen in our entangled atom example, facts about individual things would not exist in a quantum universe without decoherence. Second, as I described in a previous essay, your life plays out on one of many branches of quantum reality, a.k.a. “Worlds”. And the storyline on each branch contains only “normal” behavior — never any of the stranger things which would be allowed without decoherence, such as you walking both left and right at the same time.
So how does quantum entanglement hide itself? Recall from our example that the second type of measurement, required to demonstrate that atom 1 still has a both-path aspect to its character even after the collision, is in practice very difficult to perform. In fact, if we simply do nothing for a few moments, we will miss our chance. Gas molecules and photons in the room are constantly bouncing off the atoms, and when the first of these new collisions occurs we get a 3-particle entangled system. Confirming entanglement of two particles was already challenging, and doing so for three is exponentially harder. The underlying entangled nature of reality still always exists, but after just a more objects join the entanglement party, all hope of confirming its existence is lost. At this point decoherence is complete and the illusion of an either/or reality is overwhelming. In other words, rapid decoherence enforces the appearance of “normal”-looking behavior. How rapid are we talking about for big objects? Extremely rapid. Even a tiny 1-micron dust particle is decohered by sunlight in a nanosecond.
If we think of “you” in terms of the underlying reality masked by decoherence, it is impossible to speak of your current status without also speaking of the countless other people and things with which you are entangled. On this branch of reality you might currently be sitting next to a good friend, who on another branch was never born. However, the decohered “you” on each branch experiences the overwhelming illusion of being able to claim an unentangled corner of reality all to yourself. There is something of a paradoxical dualism here. Because of your size, you are more entangled than any single atom can ever hope to be. But precisely because you accumulate entanglements so quickly, you never seem to be entangled at all.
Why would God set up the universe this way? Why make everything part of a bigger story with unbelievably rich entangled connections, only to hide them? First, we should remind ourselves what Job, Moses, and others found when trying to question the mind of God; although welcome to ask, they got answers of a different sort than expected. Nonetheless, it is worth noting the difficulty of imagining a conscious existence in a universe where entanglement was not hidden. If decoherence did not occur, we would be unable to experience a sense of individual identity or a factual history. Thanks to decoherence, we can have self-awareness, complete with a well-defined storyline. The self-hiding nature of entanglement seems to be necessary for our rational experience. Quantum mechanics has both created for us an existential conundrum, and then solved it in a remarkable way.
It is interesting to note parallel threads in this picture of physical reality and those of various spiritual traditions, including the Christian picture of God as Trinity. Trinitarian doctrine is sometimes seen as an assertion that we cannot even begin to discuss God in our normal rational framework which insists on separating things one from another. Even when conceiving of God in multiple parts, each part is ill-defined by itself. Likewise, mystics from all spiritual traditions suggest that each of us is not as separate from the rest of the universe as we tend to think. And any Trinitarian or mystical aspect to reality is normally not easy to see, as with the quantum connections beneath physical reality. I want to be careful to not trivialize quantum physics, Trinitarian doctrine, or mysticism by implying that they are somehow equivalent or even necessarily interrelated. But I find it noteworthy that they all paint pictures of hidden connections foundational to reality.
Quantum physics unavoidably leads us to a narrative of a disconnected connectedness in the physical universe. You are entangled with starlight which passed by the Earth a million years ago, and you are entangled with people you will never meet. That is the fundamental picture, the God’s-eye view. However, the human view looks very different. You can only affect and be affected by your normal relationships in this single decohered world of our experience. And entanglement and decoherence are always acting behind the scenes, providing some of the glue necessary for our sane existence in this quantum universe.
