Before Einstein, time travel was just a story, but his calculations led us into the quantum world and gave us a more complicated picture of time. Kurt Godel found that Einstein’s equations made it possible to go back in time. What’s up? None of the ideas about how to go back in time were ever physically possible.
Before sending a particle back in time, scientists from ETH Zurich, Argonne National Laboratory, and Moscow Institute of Physics and Technology asked, “Why stick to physical grounds?
Many laws of physics treat the future and the past as if they are one thing. The second rule of thermodynamics says that in a closed system, order gives way to chaos (or entropy). When you scramble an egg to make an omelet, you add a lot of chaos to the egg, which was a closed system before.
The arrow of time is a result of the second law that can’t be changed. A process that creates entropy, like beating an egg, can’t be turned back on itself. An omelet won’t turn back into an egg, and pool balls won’t put themselves back together into a triangle on their own. Entropy moves in one direction, like an arrow, and we see this as time.
We are trapped by the second rule of thermodynamics, but a group of scientists from all over the world wanted to test it in the quantum world. Scientists used an IBM quantum computer to do this test because nature can’t do it.
Bits of data are what computers, like the one you’re using to read this, work with. A bit can be either 1 or 0. A quantum computer’s basic unit of information is called a “qubit.” A qubit can be both a 1 and a 0, which makes it much faster for the system to process data.
In a four-step experiment, the researchers used qubits to simulate subatomic particles. First, they mixed up the qubits so that what happened to one affected the others. Then, they used microwave radio pulses to change the first order of the quantum computer into a more complex one.
The quantum computer is changed by a certain algorithm to bring order out of chaos. They get hit with another microwave pulse, but this time they go back to being who they used to be. That is, they lose a millionth of a second of their age.
Valerii M. Vinokur, a scientist at the Argonne National Laboratory, says it’s like pushing against the waves of a pond to send them back to where they came from.
Since quantum mechanics is about chances, success was not a given. On the other hand, 85 percent of the time, the algorithm could make a time jump in a quantum computer with two qubits. With three qubits, the success rate dropped to about 50%. Scientists said this was because current quantum computers have flaws.
The results were just written up in a journal called Scientific Reports.
Even though the results are exciting, you shouldn’t go out and buy a flux capacitor just yet. This experiment also shows how hard it is to control even a simulated particle in time. We can’t make this kind of outside force strong enough to change even one quantum wave.
Even ONE quantum particle can’t go back in time on its own, says Vinokur, who did the research. “The system with two particles is even more irreversible than the eggs we break to make an omelette, which have billions of particles.”
In a press release from the Department of Energy, it is said that the “timeline required for [an external force] to spontaneously appear and properly manipulate the quantum waves” would be longer than the age of the universe itself. In other words, this technology is tied to quantum computing in a very specific way.
But the study isn’t just an exercise in using technology. Even though this method won’t help us make real-world time machines, it will make quantum computing better.
Kurt Godel showed that Einstein’s equations don’t make time travel impossible, but they do make it hard.