Last December, the physics Nobel Prize was awarded for the experimental confirmation of a quantum phenomenon known for more than 80 years: entanglement. As Albert Einstein and his collaborators envisioned in 1935, quantum objects can be mysteriously related even if they are separated by great distances. But no matter how strange the phenomenon may seem, why is such an old idea still worthy of the most prestigious award in physics?
Coincidentally, just weeks before the new Nobel laureates were honored in Stockholm, a different team of distinguished scientists from Harvard, MIT, Caltech, Fermilab and Google reported that they ran a process in Google’s quantum computer that could be interpreted as a wormhole. . Wormholes are tunnels through the universe that can work as a shortcut through space and time and are loved by sci-fi fans, and although the tunnel realized in this latest experiment only exists in a 2D toy universe, it could be a breakthrough for the universe. future research at the forefront of physics.
But why is entanglement related to space and time? And how could it be important for future physics discoveries? When properly understood, entanglement implies that the universe is “monistic,” as philosophers call it, that at its most basic level, everything in the universe is part of a single, unified whole. A defining feature of quantum mechanics is the description of the underlying reality in terms of waves, and a monistic universe would require a universal function. Already decades ago, researchers like Hugh Everett and Dieter Zeh showed how our everyday reality could emerge from such a universal description of quantum mechanics. But researchers like Leonard Susskind or Sean Carroll are only now developing ideas on how this hidden quantum reality might explain not only matter but also the fabric of space and time.
Entanglement is much more than just another weird quantum phenomenon. It is the principle of action behind both how quantum mechanics brings the world together and how we experience this fundamental unity as many separate objects. At the same time, entanglement is why we seem to live in a classical reality. It is literally the glue and creator of worlds. Entanglement applies to objects containing two or more components and explains what happens when the quantum principle of “anything that can happen really happens” is applied to such combined objects. Accordingly, an entangled state is when all possible combinations that the components of a constructed object might be in are superimposed to produce the same overall result. It is again the undulating nature of the quantum field that can help show how entanglement actually works.
Imagine a completely calm, glassy sea on a windless day. Now ask yourself, how can such a plane be produced by superimposing two separate wave patterns? One possibility is that overlapping two perfectly flat surfaces will still produce a perfectly flat result. But another possibility that could create a flat surface is to superimpose two identical wave patterns shifted by half an oscillation cycle, so that the wave crests of one pattern cancel out the wave troughs of the other and vice versa. If we only considered the glassy ocean as the merging of two waves, we would have no way of knowing the patterns of individual waves. What sounds perfectly ordinary when speaking of waves has the most bizarre consequences when applied to competing realities. If your neighbor told you that he has two cats, a live and a dead cat, that means either the first cat or the second is dead and the remaining cat is alive respectively – that would be a strange and sickly situation. and you may not know which one is lucky, but you get the neighbor drift. Not so in the quantum world. In quantum mechanics, the same phrase implies that two cats are combined in a superposition of cases, including the first cat alive, the second dead, and the first cat dead and the second alive; half alive and half dead, or the first cat is one-third alive, the second cat adds the missing two-thirds of life. In a quantum cat couple, the fate and circumstances of individual animals are completely resolved in the case of the whole. Likewise, there are no individual objects in a quantum universe. All that exists is combined into a single “One”.
“I’m almost certain that space and time are illusions. These are primitive concepts that will be replaced by something more sophisticated.“
— Nathan Seiberg, Princeton University
Quantum entanglement shows us a vast and entirely new region to explore. It defines a new foundation of science and subverts our search for a theory of everything to build on quantum cosmology rather than particle physics or string theory. But how realistic is it for physicists to follow such an approach? Surprisingly, this is not only unrealistic, in fact, they are already doing this. Researchers at the forefront of quantum gravity have begun to rethink space-time as a result of entanglement. An increasing number of scientists began to base their research on the inseparability of the universe. By following this approach, hopes are high that they will finally be able to grasp what space and time really are in the depths of the foundation.
Whether space is stitched together by entanglement, abstract objects from physics, space and time beyond, or the field of possibilities represented by Everett’s universal wave function, or everything in the universe can be traced back to a single quantum object – all these ideas can be traced back to a different commonality. shares the point. monistic flavor. Currently, it is difficult to judge which of these ideas will determine the future of physics and which will eventually disappear. Interestingly, although initially the ideas were often developed in the context of string theory, they seem to have surpassed string theory and strings no longer play any role in the latest research. A common thread now seems to be that space and time are no longer considered fundamental. Contemporary physics does not begin with space and time to continue with this pre-existing background set. Instead, space and time themselves are considered products of a more fundamental reality projector. “I’m almost certain that space and time are illusions,” said Nathan Seiberg, a leading string theorist at the Princeton Institute for Advanced Study. These are primitive concepts that will be replaced by something more sophisticated.” Moreover, in most scenarios that propose emerging spacetimes, entanglement plays a fundamental role. As philosopher of science Rasmus Jaksland has pointed out, this ultimately means that there are no longer individual objects in the universe; “To adopt entanglement as the world-forming relationship comes at the expense of separability. But those who are ready to take this step should look to entanglement for the fundamental relationship that will perhaps constitute this world (and perhaps all other possible ones).” Thus, when space and time disappear, a unified One emerges.
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Conversely, from the perspective of quantum monism, such mind-blowing consequences of quantum gravity are not far off. Already in Einstein’s general theory of relativity, space is no longer a static phase; rather due to the masses and energy of matter. It defines the relative order of things, much like the view of the German philosopher Gottfried W. Leibniz. If now, according to quantum monism, there is only one thing left, there is nothing to be organized or organized, and finally the concept of space is no longer needed at this most basic level of definition. It is the “One”, a single quantum universe that makes up space, time, and matter.
Leonard Susskind boldly argued in an open letter to quantum information science researchers: General relativity is nothing more than quantum mechanics; completely understood. As Sean Carroll points out, “Maybe quantifying gravity was a mistake and space-time was lurking in quantum mechanics all along.” For the future, “rather than quantifying gravity, perhaps we should try to attract quantum mechanics. Or, more accurately, but less evocatively, “find gravity within quantum mechanics,” suggests Carroll on his blog. Indeed, it seems that quantum mechanics has been serious all along. Many of the deadlocks in the discovery of quantum mechanics could have been avoided if it were taken, understood as a theory realized not in space and time but in a more fundamental projector reality. Quantum gravity could have been avoided. If we had validated the monistic results of quantum mechanics as early as Everett, the legacy of a three-thousand-year-old philosophy that has been the legacy of a three-thousand-year-old philosophy, and Zeh had drawn attention to the influential quantum pioneer Niels Bohr’s pragmatic interpretation of quantum mechanics as a tool, rather than clinging to them, he was on the way to uncovering the foundations of reality. We would have progressed further.
Adapted from One: How an Ancient Idea Holds the Future of Physics By Heinrich Päs. Copyright © 2023. Available from Basic Books, an imprint of Hachette Book Group, Inc.
