Fans of “The Rocky Horror Picture Show” know one thing about time — it’s fleeting. We also know that time only goes one direction — forward. That concept is called the “arrow of time,” and it basically just states that time moves from the past to the future. The second law of thermodynamics — that “total entropy of an isolated system can never decrease over time” — is very closely related to this concept. It would seem all this rules out the possibility of time travel, since going backward in time is, quite literally impossible.
Or is it?
Researchers at the Moscow Institute for Physics and Technology just published a study in conjunction with teams in Switzerland and the United States in which they took a quantum computer and got it to reverse itself by an entire second. Let’s just make sure we say from the outset that this will need to be repeated a few dozen times, but there’s no denying that this is a major breakthrough. In fact, the study is published in Nature, which is a fairly major institution that probably wouldn’t want to risk its reputation printing junk.
This particular team has been studying quantum physics in this regard for some time, and this study is just the latest that they’ve published. Lead author Gordey Lesovik explained the studies.
“We began by describing a so-called local perpetual motion machine of the second kind. Then, in December, we published a paper that discusses the violation of the second law via a device called a Maxwell’s demon,” Lesovik said. “The most recent paper approaches the same problem from a third angle: We have artificially created a state that evolves in a direction opposite to that of the thermodynamic arrow of time.” (Phys.Org)
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In order to better understand the study, Phys.Org explained the difference between the past and the future, because that observation is key to whether time can be reversed. They described a scenario in which you’d record two identical billiard balls colliding. If you played the footage in reverse, the quantum equation would stay the same for the results, both forward and backwards. But if you change the setup, and make it so that one ball is crashing into a bunch of them, then you get to observe what makes the past and the future different. Namely, it’s our own basic understanding of how our universe works.
However, imagine recording a cue ball breaking the pyramid, the billiard balls scattering in all directions. In that case, it is easy to distinguish the real-life scenario from reverse playback. What makes the latter look so absurd is our intuitive understanding of the second law of thermodynamics—an isolated system either remains static or evolves toward a state of chaos rather than order.
Most other laws of physics do not prevent rolling billiard balls from assembling into a pyramid, infused tea from flowing back into the tea bag, or a volcano from “erupting” in reverse. But these phenomena are not observed, because they would require an isolated system to assume a more ordered state without any outside intervention, which runs contrary to the second law.
So basically, Dr. Lesovik’s team decided to repeat the billiard ball exercise in their own experiments. Except, instead of billiard balls, they used isolated electrons in an empty space.
“Suppose the electron is localized when we begin observing it. This means that we’re pretty sure about its position in space. The laws of quantum mechanics prevent us from knowing it with absolute precision, but we can outline a small region where the electron is localized,” says study co-author Andrey Lebedev from MIPT and ETH Zurich.
What they observed is that thanks to Schrödinger’s equation, even though there is no observable difference between the past and present, there is a spreading of the space around an electron. This leads to a chaotic bit of entropy being introduced, and it has a parallel to the billiard ball experiment.
The physicist explains that the evolution of the electron state is governed by Schrödinger’s equation. Although it makes no distinction between the future and the past, the region of space containing the electron will spread out very quickly. That is, the system tends to become more chaotic. The uncertainty of the electron’s position is growing. This is analogous to the increasing disorder in a large-scale system—such as a billiard table—due to the second law of thermodynamics.
Here’s a representation of the four stages Lesovik’s researchers undertook in their experiment, and how it relates tot he billiard table analogy.
As a result of the chaos, it’s possible for “complex conjugation” to take place, which in turn “smears” an electron. That smearing sends the electron back into “small region of space over the same time period.”
“Mathematically, it means that under a certain transformation called complex conjugation, the equation will describe a ‘smeared’ electron localizing back into a small region of space over the same time period.” Although this phenomenon is not observed in nature, it could theoretically happen due to a random fluctuation in the cosmic microwave background permeating the universe.
Essentially, what they found is that in a natural state, an electron can theoretically go back in time all on its own. Next, it was time for the team to figure out if they could “reverse time” on demand. But this time, instead of using a single electron, the built a quantum computer from two and three quibits, which Phys.org describes as “basic elements.” Then, they attempted to replicate the billiard ball/electron experiment in four unique stages.
Stage 1: Order. Each qubit is initialized in the ground state, denoted as zero. This highly ordered configuration corresponds to an electron localized in a small region, or a rack of billiard balls before the break.
Stage 2: Degradation. The order is lost. Just like the electron is smeared out over an increasingly large region of space, or the rack is broken on the pool table, the state of the qubits becomes an ever more complex changing pattern of zeros and ones. This is achieved by briefly launching the evolution program on the quantum computer. Actually, a similar degradation would occur by itself due to interactions with the environment. However, the controlled program of autonomous evolution will enable the last stage of the experiment.
Stage 3: Time reversal. A special program modifies the state of the quantum computer in such a way that it would then evolve “backwards,” from chaos toward order. This operation is akin to the random microwave background fluctuation in the case of the electron, but this time, it is deliberately induced. An obviously far-fetched analogy for the billiards example would be someone giving the table a perfectly calculated kick.
Stage 4: Regeneration. The evolution program from the second stage is launched again. Provided that the “kick” has been delivered successfully, the program does not result in more chaos but rather rewinds the state of the qubits back into the past, the way a smeared electron would be localized or the billiard balls would retrace their trajectories in reverse playback, eventually forming a triangle.
What Lesovik and his team discovered was that in in the computer built with two quibits, there was a pretty consistent reversal of time. In the computer with three of the quibits, more errors were discovered.
The researchers found that in 85 percent of the cases, the two-qubit quantum computer returned back into the initial state. When three qubits were involved, more errors happened, resulting in a roughly 50 percent success rate. According to the authors, these errors are due to imperfections in the actual quantum computer. As more sophisticated devices are designed, the error rate is expected to drop.
Lesovik believes these experiments could even be used to calibrate quantum computers in the future. Again, it can’t be stated enough that while they were able to “reverse time” in a very specific way using a very complex equation run on a quantum computer, these tests have to be repeated quite a bit before we start looking for ways to put a Mr. Fusion on top of our electrical DeLoreans.
Writer/comedian James Schlarmann is the founder of The Political Garbage Chute and his work has been featured on The Huffington Post. You can follow James on Facebook and Instagram, but not Twitter because he has a potty mouth.
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