A 10 rarely happens for a master’s degree, but Frank Sumhurst got it. “This project deserves the highest score possible,” says his supervisor Gilmer Renema, who has never before been awarded a 10. The other examiners thought so, too.
Somhurst completed his studies in applied physics at the University of Twente last year. His research has now been published in a journal Nature Communications. It’s an experimental breakthrough in a paradox that has plagued physics since the 1930s.
Then quantum physics was developed, which is the physics of the youngest. Quantum theory has been hugely successful in explaining the nature and behavior of elementary particles. But the theory contained phenomena that physics had not known before, and that we do not experience in our great universe. For example, time in our world cannot be reversed. In quantum theory, yes. Rinema says time must be reversible there, or else the theory would fail.
Glass that shatters on the floor is irreversible; Shards never automatically turn back into glass. Classical physics says that disorder, the ‘entropy’, increases. There is no other way, says classical physics. By definition, disorder increases. This gives time its direction.
But it is different in quantum physics. At this time, time has no direction, and there is no arrow pointing in the direction of increasing chaos. In the world of elementary particles, order is preserved, says quantum theory.
Now you can say: there is a good theory for the smallest, the quantum theory, in which order is preserved, and a good theory for the macrocosm, thermodynamics, in which disorder increases and we see glasses littering the Earth every day. What are you worried about? Why should these two physicists be combined?
Somehurst: “You could say that. But if you start with the elementary particles, the quantum world, and you expand, you end up in the world we’re observing. Two different theories for these two worlds mean there must be a transition somewhere in that expansion. That would It interrupts reality. That’s not possible.”
The solution exists in theory
So that paradox that has existed for nearly a century must be resolved. And in theory, this has been done for some time. The solution lies in a phenomenon all too common in the quantum world: entanglement, which is the phenomenon that two particles that are in contact with each other in a certain way remain connected, no matter how far apart they are.
Renema: “After entanglement you have a system that has two parts. You can look at the perturbation of the whole system, but also the two subsystems. Then you see that the perturbation of the subsystems can increase, while they continue to align themselves. Entanglement is the link between quantum theory of elementary particles and dynamics thermodynamics of our world.
Although abstract, this still seems rather simple. And according to physicists who have mastered the complex mathematics of quantum theory, it can work this way. But physics also wants to see experimental evidence. And that’s very difficult, says Renema, who worried six years ago about the experiment that Sumhurst has now come to a successful conclusion. “It feels very good that we have succeeded now.”
This beautiful feeling is due to the technology developed on the Enschede campus. Renema leads a research group at the university, but also leads a company (Quix Quantum) that builds optical quantum processors. These are chips that work with light, that is, with the quantum properties of light particles. This technology provides unprecedented control over elementary particles, Renema says: “We are the only ones in the world who can do this.”
Because particles are just like people. As soon as you start working with it, noise and friction arise, information leaks away, you get empty phrases and echoes. You have to get all of that under control.
Dining table with mirrors and lenses
Somhorst shows the setup in the lab. A plateau the size of a dining table, with a laser source, a large set of mirrors, lenses and other devices, and in the center a small chip with double-sided fiber optic connections.
The foil is a kind of organizing arena for the light particles entering the front. The entire initial process of mirrors, lenses and more was done to bring light particles with finely tuned quantum properties onto the chip.
It should happen right there, in the conversion yard. There are light nodes and switches that must be programmed in such a way that entanglement is created between the light particles. Upon exiting the wafer, light travels through the glass fibers to detectors that measure the state of the light particles.
For Somhorst, this major project was a tour de force. “What did I start with, I thought. The problem was known, but every post about it was a mystery to me. And how do you translate this into an experiment?” That means putting a lot of ideas down on paper, breaking them down and throwing them away, says Sumhurst. “And then, it’s a lot of work to properly program those points on the chip.”
Naivety can help
Renema says Somhorst makes his role smaller than it was. “We were able to make progress because Frank looked at the problem with different eyes. This photonic processor is a quantum system. And in it you must prove thermodynamic states that obey the laws of those other physics. Theoretical physicists can ponder this endlessly, but Frank , an applied physicist, says, “If it’s a thermodynamic system, we should be able to see this and that. There was no theory about it. He invented it.”
“I was standing at the herring cart when he called me and dropped a penny,” Renema says. “It can help in physics to be silly and to take things literally.”
This is the first experimental demonstration that macro-world physics, thermodynamics and increasing turbulence, can be brought into the quantum realm without violating the laws of quantum theory. Indeed, it has been shown here that even in the quantum world, elementary particles can shatter glass on the ground. And the great thing is that the pieces here can turn into glass again.
The quantum computer from Twente conquers Europe
While people in Delft were searching in vain for an exotic particle to build a quantum computer, a light-powered quantum computer was being developed on the other side of the country, in Twente. The Twente account miracle is now the norm in Europe.
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