Through the years, people have collected a
whole dictionary of phrases about wasting time and how it can never be turned back. It would be a shame to lose them all if some
scientist were to prove that time is reversible. Actually, it seems like that already happened! Well kinda… Time travel might just be real. No one could call you a slacker or a procrastinator. Time is always on your side; you can beat
the clock 10 times out of 10, and even unscramble all the metaphorical eggs you want. If you’re a single quantum in highly improbable
circumstances, simulated inside a quantum computer, of course. And even then, it probably wouldn’t be as
simple as it sounds. Did anybody understand what I just said? Me neither. Let’s continue, shall we? A team of Russian scientists from the Moscow
Institute of Physics and Technology stated in a press release that they were able to
reverse the state of quantum in time for a minuscule fraction of time. For this purpose, they used an IBM quantum
computer and innumerable attempts, 85% of which were successful in a simple system,
and only 45% in a system that’s a bit more complicated. But simple isn’t exactly the right word
here. Nothing can be simple if you’re talking
about quantum computers and quantum physics in general. The easiest way to imagine what really happened
during these experiments is to take a ball and throw it at the wall. It’ll bounce right back into your hands. Under the right circumstances, like the force
you apply to the ball, and the angle at which it strikes the wall, it’ll return to you
while flying the same path at the same speed as when it went to the wall in the first place. Now let’s try another example. This time, you’re throwing a marble; it
strikes the wall and breaks as expected, then falls down. But look, now it’s going back on the same
trajectory, flies up, bounces off the wall, and finally lands back in your hand while
reassembling into one piece. Did you notice the difference between those
two examples? In the first case, the ball returned to its
default position without violating the natural flow of time. It just copied its own trajectory. Even if you decide to watch it on rewind,
nothing will visibly change here. Looks convincing, but it has nothing to do
with reversing time. It’s just that circumstances allow the ball
to return to its exact previous state and position. But the situation with the glass marble is
much more interesting because if we put what happened on rewind, we can clearly see how
the marble changes its state, which can’t be reversed in a linear flow of time from
past to future. Now it’s cracked, but a moment later it’s
whole again. Or a moment before? How do you even explain it with words when
time suddenly starts to go south like this? Unfortunately, it’s not entirely clear from
the publication of the Russian physicists what their finding is closer to: a simple
rewind that only visibly reverses time, or the complete time reversal of a quantum. Either way, it was supposed to be completely
impossible to bring a quantum into its previous state. The concept of the arrow of time is an integral
part of nature’s laws, like the laws of thermodynamics for example. The second law of thermodynamics dictates
that every closed system, whether it consists of just one elementary particle or of everything
there is in the Universe, is constantly moving towards disorder, and this process is both
unstoppable and irreversible. Basically, it means that time always goes
in only one way: from past to future as everything is constantly, irreversibly changing its state
and condition. Nothing ever stays the same – that’s a
simple truth we all know, even without special expertise in physics. But the quantum world is kind of used to breaking
all of our expectations at this point. Quantum can be in two states simultaneously. Quantum teleportation was proved to be real,
and now it seems like even time itself isn’t truly safe. But among those miracles, the last one is
particularly improbable, because it can only happen in the simplest systems, and only in
circumstances simulated in quantum computers. A quantum computer is a real miracle of science,
with vast processing power that comes with one main difference from the classic computers:
classic silicon-based computers use bits to store information. A bit is a basic unit of measurement that
serves to contain data in a sequence of bits, with each one giving only one of two possible
outputs: 0 or 1. Every single bit of memory is useless outside
the sequence, but many bits combined can become a code that could mean anything – from a
singular digit to a picture of a cat. Zeros in this sequence are bits that don’t
get to be electrically charged, and ones are those that are powered. This is how memory works in your computer
or smartphone. Quantum computers use quantum bits or qubits
instead of bits. These are also the most basic units of information
for a quantum computer. The difference is that computers using qubits
have much more potential processing power than a classic computer. When bits can only be in one of the two possible
states, qubits use quantum particles, which can be not only in one of two states, but
also in both at the same time. This can be explained by the fact that elemental
particles like photons and electrons, which are used in qubits, can be in a state known
as a superposition. It’s easy to represent as both 0 and 1,
and anything in between. This can give many more possible meanings
to one qubit, so it’ll have more potential for computing. The only problem is that the superposition
of particles is quite unstable and can be disrupted even by looking at them and trying
to read the output in any other direct way. When disturbed, particles will immediately
go from a superposition to one of the two main states. The difficulty of coming up with indirect
methods of reading qubits’ output led to the slow growth of quantum computing. More than half of the ideas related to it
are still highly theoretical, and the most complex quantum computer still has only 16
qubits. For a time-reversal experiment, only two qubits
were used, and even if it wasn’t true time-reversal, it’s a giant breakthrough for quantum computing
itself. The result of these experiments shows that
by applying a special equation to qubit particles, they can effectively step back in their state
like after a good sip from the Fountain of Youth. This may allow quantum computers to backtrack
the progress of processing information. This way it’ll be possible to better test
quantum programs. It’s basically an undo button for quantum
processes! Another borderline impossible feat of the
quantum world is quantum teleportation. A group of computer scientists was able to
basically transport a particle through space in an instant. One moment it was there, and then it blinked
in another place! But once again, it’s not science fiction;
not everything is what it seems at first glance. To be fair, there were initially two particles
linked to each other by a special kind of relation in quantum physics called entanglement. Then they were separated from one another
and one of them was thoroughly scanned. As we already know, scanning a particle applies
stress on it, and therefore disrupts its state almost completely. Basically, after the scan, one of the particles
became something completely different from what was scanned. Information about the properties of this particle
was then sent to the second particle and it inherited them all, effectively becoming the
first particle. I bet you can spot the problem here. None of the particles were really transported
anywhere, but the information about them was teleported. And in basic terms, teleportation means scanning
and disrupting something in one place and reassembling it in another with the use of
information from the scan. Therefore, what scientists saw there was still
teleportation. Quantum teleportation, just like quantum time-reversal,
can’t be used on anything except particles, like electrons and photons, so it’s actually
too soon to get your hopes up for getting to work in the blink of an eye, or to turn
back time and wake up earlier to be on time. But who knows what could be possible if all
this new knowledge could be used to build the first practical quantum computers. With their processing powers, we’ll be able
to take chances even on teleportation and time machines. What? A person can dream! Hey, if you learned something new today, then
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