In November, physicists using Google’s Sycamore quantum computer in the US performed a calculation that is equivalent to sending matter through a “wormhole”, a shortcut through the fabric of spacetime. What this means for physics is a matter of controversy. But physicists themselves believe they have demonstrated a way to reveal deep connections between two seemingly incompatible theories: quantum theory and Einstein’s theory of gravity.
Both theories reign supreme in their own fields: quantum theory in the ultra-small realm of atoms and their constituents, and Einstein’s theory in the ultra-large world of stars and the Universe. However, during the Big Bang, the ultra-large universe was ultra-small. So if we ever want to understand the origin of everything, we have to unite quantum theory and Einstein’s theory of gravity.
The problem is that they seem fundamentally incompatible: Whereas Einstein’s theory is based on certainty – describing, for example, the exact trajectory of the planet through space; Quantum theory is based on uncertainty and only describes the chance, or “probability”, that an atom will follow one of many possible paths through space.
Surprisingly, however, physicists have found a tantalizing connection between the two theories that hints that, despite their incompatibility, they are just different sides of the same coin.
In 1997, Professor Juan Maldacena of the Institute for Advanced Study at Princeton discovered that Einstein’s theory in the 3D universe is a kind of holographic projection of quantum theory that lives on the 2D frontier of the Universe. The problem is that this duality only works in a bounded Universe while we live in an ever-expanding Universe.
Basically, for the current work, physicists have discovered that there is also a duality between a wormhole and a particular computation on a quantum computer. It is a device that can outperform a normal computer because, instead of manipulating bits, which can represent a 0 or a 1, it manipulates quantum bits, or qubits, which can be a 0 and a 1 in same time. In 2016, Professor Daniel Jafferis, Dr Ping Gao and Dr Aron Wall of Harvard University discovered a theoretical wormhole that is the duplicate of a particular computation on a quantum computer.
What makes all this remarkable is that in 1935 Einstein published two papers, not considered his greatest and which seemed unrelated even to Einstein. The first, with Nathan Rosen, and known as ER, showed that his theory of gravity allows for the existence of wormholes.
The second paper, with Rosen and Boris Podolsky, and known as EPR, showed that subatomic particles born together are then bound forever by a “spooky action at a distance”, or “entanglement”: when one is disturbed, the other reacts instantly, even if on the other side of the Universe. In 2013, Maldacena and Professor Leonard Susskind of Stanford University assumed that ER = EPR. In other words, subatomic particles can instantly influence each other because they are connected by a wormhole.
Now, Jafferis and his colleagues have implemented a quantum computation that is equivalent to sending matter through a wormhole. Achieving this was something of a tour de force because the Sycamore computer, housed at Google Quantum AI in Santa Barbara, California, has terribly limited capacity – it can only handle 54 qubits – and has a high error rate . However, they trained a neural network to drastically reduce the number of steps needed to compute them while preserving its essential nature.
The calculation produced exactly the signal they expected if it perfectly mimicked the passage of matter through a wormhole. Team member Professor Maria Spiropulu, who worked at the Large Hadron Collider at CERN, near Geneva, says it was as exciting a moment as seeing the signal from the Higgs boson in 2012.
“It is important to understand that experiments of this type are not simulations, but actually involve real phenomena. The wormhole in the laboratory experiment is as real as it would be if it connected two holes astronomical blacks,” says Susskind.
“The experimental attention to the new paradigm that quantum theory and Einstein’s theory of gravity, when interpreted through the holographic principle, are almost the same thing, will accelerate the paradigm shift. “
What all of this means for physics is controversial. Some say this tells us little since the experiment is about a Universe that is not ours and is just a 1D “toy model” anyway. Others say it demonstrates that experiments like this can reveal the connections between quantum theory and Einstein’s theory of gravity and help us find the elusive theory of quantum gravity that will tell us how the Universe has begun.
More like this
Learn more about cosmology: