Can scientists reverse time with a quantum computer?

The universe becomes messy. Like a glass breaking in pieces or a single wave crashing on the shore, the mess of the universe can only go in one direction – towards more chaos and disorder. But scientists think that, at least for a single electron or the simplest computer, they could possibly go back in time and restore order in chaos. This does not mean that we will soon be visiting dinosaurs or Napoleon, but for physicists, the idea that time can flow is always a big deal.

Normally, the tendency of the universe to disorder is a fundamental law: the second law of thermodynamics. He says more formally that any system can only pass more and more unordered, and that the chaos or disorder of a system – its entropy – can never diminish. But an international team of scientists led by researchers from the Moscow Institute of Physics and Technology thinks they have discovered a loophole.

Computing power

For their experiment, scientists used IBM's simple public quantum computer program, which uses two qubits – two units that, like a regular computer bit, can be one or zero. But unlike conventional computer bits, qubits can also take a form called superposition, where they are both one and zero at the same time. In this way, they follow the laws of quantum mechanics, which are less pronounced than the classical world.

Scientists have configured the computer so that the two qubits are zeros. According to quantum laws, the mere passage of time will bring the computer down in that order, so that qubits will soon find themselves in a random assortment of ones, zeros, or both. But scientists can also do this by running a program on their simple 2-qubit computer.

The scientists then ran a different program, which tells the computer to run "backwards". They then ran the first program again and were able to recover their initial zero zero state about 85% of the time. They published their results on March 13 in Scientific reports.

The trickiest part of the program is asking the computer to work backwards, so that time goes back. Scientists have studied this "in nature" by isolating a single electron and calculating the time it would take for random perturbations of the universe to produce such an effect. They discovered that even if they studied 10 billion electrons every second, it would take the whole life of the universe for such a phenomenon to happen once.

This is why you will never drop a handful of glass fragments and will see them approaching each other to form an uninterrupted mirror, while a fallen mirror will almost always split into several pieces. The system will always tend to mess.

But by forcing the order out of the mess with a quantum computer program, scientists may have found a way around this fundamental physical law.