How scientists made time flow backwards (with a quantum computer)

How scientists made time flow backwards (with a quantum computer)

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Scientists designed an ingenious experiment for a quantum computer to revert to the state it had a fraction of a second in the past.

For a fraction of a second, they achieved something that seemed impossible.

Researchers at the Institute of Physics and Technology of Moscow (IFTM) along with scientists in the United States and Switzerland managed to get a quantum computer to revert to the state that had a fraction of a second in the past.

In other words, they managed to get time back in that quantum domain.

The experiment seems to contradict a basic law of physics, the second law of thermodynamics.

“This law is closely related to the notion of time as an arrow that moves only in one direction, from the past to the future,” said Gordey Lesovik, IFTM scientist and lead author of the study published in the journal Scientific Reports.

” We have artificially created a state that evolves in a direction opposite to that of the time arrow of thermodynamics,” he added.

Why do not we see an upside-down eruption?

What differentiates the future from the past?

Most laws in physics do not distinguish between the future and the past.

We can understand this, the researchers point out, considering an equation that describes the collision and rebound of two billiard balls.

Illustration of a clock and time flowing in one direction
Copyright of the GETTY IMAGES imageImage caption “The second law of thermodynamics is closely related to the notion of time as an arrow that moves only in one direction, from the past to the future,” Lesovik said.

 

If we recorded the shock with a camera and then saw the tape in reverse, the movement in both directions could be represented by the same equation.

However, if we imagine a recording in which the balls are seen to disperse in all directions when hit by a billiard stick, and we see the film upside down, what we see will seem unlikely.

And that is due to our intuitive understanding of the second law of thermodynamics , which states that an isolated system either remains closed or evolves into a more chaotic state, but never into a more orderly one.

Most other laws of physics do not prevent the balls from settling themselves alone in a triangle, or that tea diffused in an infusion may flow back into the tea bag, or that the lava will return to a volcano in a rash in reverse, the scientists point out.

We do not see any of that happening in the world around us, because that would require an isolated system to assume a higher order state without any intervention, something that goes against the second law of thermodynamics, a law “whose intimate nature it has not yet been explained in detail. “

Quantum bits

If we do not see that time flows back into the observable world, how did the scientists make that happen?

The “time machine” used by researchers is a quantum computer.

Illustration of a 1 and 0
Copyright of the GETTY IMAGES imageImage caption Unlike the traditional bits of digital computing, a cube can take the value 0, 1 or 0 and 1 at a time.

 

In traditional digital computing, a bit or unit of information can only take two values: 0 or 1.

In contrast, in quantum computing, cubes or quantum bits are used, which use the incredible properties of subatomic particles.

Electrons or photons, for example, can present two states at once, a phenomenon called superposition.

As a result, a computer based on cubits can do many more calculations at a higher speed than a conventional machine.

“A kick to a pool table”

Lesovik and his colleagues designed an ingenious experiment .

They used a program that converts the initial state of the cubits into an IBM quantum computer into a changing and increasingly complex pattern of zeros and ones.

In this process the order is lost, in the same way that the billiard balls formed in a triangle disperse when they are hit by another ball driven by a billiard stick.

Pool balls
Copyright of the GETTY IMAGES imageImage caption The experiment is equivalent to “kicking a pool table so that the balls rearrange themselves again in their triangle formation”.

 

Another program then modified the state of the quantum computer in such a way that it evolved backwards, from chaos to order.

In other words, the state of the cubits returned to its initial position.

The experiment is equivalent to “kicking a pool table so that the balls rearrange themselves again in their triangle formation,” according to the researchers.

Applications

The scientists found that the quantum computer of two cubits returned to its initial state in 85% of cases. But when three cubits were used, the error rate was 50%.

This is due to imperfections in the design of quantum computers that could be overcome in the future, according to scientists.

IBM researchers with a quantum computer
Copyright of the IBM imageImage caption The IBM quantum computer stores superconducting cubes at extremely low temperatures.

 

The experiment is far from suggesting that we can travel in time in the future.

But it could have practical applications.

“Our algorithm could be updated and used to test and undermining errors in programs written for quantum computers,” Lesovik said.

Scientists could verify that the software of a quantum computer is working correctly by causing it to go back in time.

And any advance in the development of quantum computers, the “holy grail” of computer science, could have consequences for all.

Computer scientists say that quantum computers could accelerate the discovery of new drugs, decipher the most complex cryptographic security systems, help design new materials and model climate change more accurately.

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