Last December, the Nobel Prize in physics was awarded for the experimental confirmation of a quantum phenomenon known for more than 80 years: entanglement. As envisioned by Albert Einstein and his collaborators in 1935, quantum objects can be mysteriously connected even if they are separated by great distances. But as strange as this phenomenon may seem, why does such an old idea still deserve the most prestigious prize in physics?
Coincidentally, a few weeks before the new Nobel laureates were awarded in Stockholm, a group of distinguished scientists from Harvard, MIT, Caltech, Fermilab and Google announced that they had carried out a process that could be interpreted as a wormhole in Google’s quantum computer. . Wormholes are tunnels in the universe that can act as a shortcut through space and time and are beloved by science fiction fans, and the tunnel realized in this latest experiment, although it only exists in a 2D toy universe, may represent a leap into the future. research is at the forefront of physics.
But why is entanglement related to space and time? And how could it be important for future physics breakthroughs? Entanglement, properly understood, implies that the universe is, as philosophers say, “monistic,” that at its most fundamental level, everything in the universe is part of a single, unified whole. A defining feature of quantum mechanics is that its underlying reality is described 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 the reality of our everyday life can emerge from such a universal quantum-mechanical description. But only now are researchers like Leonard Susskind or Sean Carroll developing insights into how this hidden quantum reality can explain not only matter, but also the structure of space and time.
Entanglement is more than just another strange quantum phenomenon. This is the operating principle behind both why quantum mechanics holds the world together and why we perceive this underlying unity as many separate objects. At the same time, entanglement is the reason we live in classical reality. It is literally the glue and creator of worlds. Entanglement refers to objects made up of two or more components and describes what happens when the quantum principle “whatever can happen does happen” is applied to such entangled objects. Consequently, an entangled state is the superposition of all possible combinations that the components of a composite object can enter to produce the same overall result. Still, the wavelike nature of the quantum domain can help show how entanglement actually works.
Imagine a perfectly 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 superimposing two perfectly flat surfaces again results in a perfectly level result. But another possibility that could produce a flat surface is to superimpose two identical wave patterns shifted by half an oscillation period, so that the wave crests of one pattern cancel out the wave troughs of the other, and vice versa. If we were to observe the glassy ocean, if we considered it as the result of the fusion of two swells, there would be no way for us to learn the patterns of the individual swells. What sounds completely ordinary when talking about waves has the strangest consequences when applied to the realities of competition. If your neighbor told you that he has two cats, one alive and one dead, that means either the first or the second is dead and the other cat is alive – that would be weird and sick. way to describe pets and you won’t know which one is lucky, but you’ll get the neighbor’s drift. Not so in the quantum world. In quantum mechanics, the same expression implies the possibility that two cats are combined in a superposition, including the possibility that the first cat is alive, the second is dead, and that the first cat is dead while the second is alive, and that both cats exist. half alive half dead or the first cat is one third alive and the second cat adds two thirds of life lost. In quantum double cats, the fate and conditions of individual animals are completely resolved as a whole. Similarly, there are no individual objects in the quantum universe. All that exists is united in a single “One”.
“I am almost certain that space and time are illusions. These are rudimentary concepts and will be replaced by something more complex.“
— Nathan Seiberg, Princeton University
Quantum entanglement opens up a vast and entirely new area for us to explore. It defines a new foundation for science and transforms our search for a theory of everything—based not on particle physics or string theory, but on quantum cosmology. But how realistic is it for physicists to take such an approach? Amazingly, it’s just not realistic – they’re already doing it. Researchers at the forefront of quantum gravity have begun to rethink space-time as a consequence of entanglement. An increasing number of scientists began to base their research on the indivisibility of the universe. Hopes are high that with this approach, they can finally understand what space and time are deep within the foundation.
Whether space is entangled, physics is described by abstract objects beyond space and time, or the space of possibilities represented by Everett’s universal wave function, or everything in the universe is traced back to a single quantum object—all these ideas share differences. monistic flavor. At present, it is difficult to judge which of these ideas will inform the future of physics and which will eventually disappear. Interestingly, although the ideas were originally developed often in the context of string theory, they seem to have left string theory behind, and strings no longer play a role in the latest research. A common theme now is that space and time are no longer considered fundamental. Modern physics does not begin with space and time to proceed with things placed in this pre-existing background. Instead, space and time themselves are considered products of a more fundamental projector reality. Nathan Seiberg, a leading string theorist at the Institute for Advanced Study in Princeton, said, “I’m pretty sure that space and time are illusions. These are rudimentary concepts and will be replaced by something more complex.” Moreover, entanglement plays a key role in most scenarios that suggest extraordinary space-times. As the philosopher of science Rasmus Jaxland points out, this ultimately suggests that there are no longer individual bodies in the universe; says that everything is connected to everything else: “Accepting entanglement as connectedness of the world comes at the cost of refusing to separate. But those who are willing to take that step may need to search for the ultimate connection that makes up this world (and perhaps all other possible ones).” Thus, when space and time disappear, a single One emerges.
Courtesy Hachette Book Group
On the contrary, from the point of view of quantum monism, such implausible consequences of quantum gravity are not far off. Space is no longer a static stage in Einstein’s theory of general relativity; rather it is caused by the mass and energy of matter. Like the German philosopher Gottfried W. Leibniz, it describes the relative order of things. If now, according to quantum monism, only one thing remains, there is nothing left to order or to order, and finally, at this most fundamental level of description, there is no need for a concept of space. It is the “One,” the unified quantum universe that makes up space, time, and matter.
“GR=QM” Leonard Susskind boldly asserted in an open letter to researchers in quantum information science: general relativity is nothing more than quantum mechanics—a hundred-year-old theory that has been applied to all sorts of things with great success but never really fully understood. As Sean Carroll points out, “Perhaps quantizing gravity was wrong, and spacetime was hidden in quantum mechanics all along.” For the future, “rather than quantizing gravity, perhaps we should try to gravitate quantum mechanics. Or, more accurately, but less passionately, ‘find gravity in quantum mechanics,'” Carroll suggests on his blog. Indeed, it seems that if quantum mechanics were to be taken seriously in the first place, it is not what happens in time and space. , if understood as a theory that takes place within a more fundamental projector reality, the exploration of many is at a dead end. quantum gravity could be avoided. If we accept the monistic implications of quantum mechanics—accepted in antiquity, persecuted in the Middle Ages, revived in the Renaissance, and in Romanticism— If we were to acknowledge the legacy of three thousand years of falsified philosophy—as Everett did, and Zeh pointed out to them—rather than sticking to the instrumentalist interpretation of quantum mechanics by the influential quantum pioneer Niels Bohr, we would be on the way to elucidating the foundations of reality.
adapted 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.
