There’s a Secret Way to Get to Absolute Zero. Scientists Just Found It.
Researchers just found a new way to get an object to absolute zero.
We’ve known that it could be done with infinite time or infinite energy, but the team just discovered that it can also be done if you have infinite control over an infinitely complex system.
Because hitting absolute zero is the same as fully deleting information from a quantum system, this highlights a known limitation of quantum computing.
We’re not getting to absolute zero anytime soon. The temperature at which all energy in an object drops to zero, our inability to reach it is enshrined in the third law of thermodynamics.
One version of the law states that in order to reach absolute zero, we’d have to either have infinite time or infinite energy. That’s not happening any time soon, so out the window go our hopes of achieving a total lack of energy.
Or do they?
A team from the Vienna University of Technology in Austria wanted to see if there was alternate route to absolute zero. And they found one in an interesting place—quantum computing.
The researchers entered into their research with the intent of trying to generate a version of the third law of thermodynamics that jived cleanly with quantum physics. Because the regular version that so many physicists know and love doesn’t quite fit nicely into the quantum world.
Disagreements between classical and quantum physics happen all the time—it’s why so much time and effort goes into trying to find a unified theory of physics that encompasses both sets of rules. That doesn’t mean classical physics is wrong, it just means it’s limited in ways that we didn’t expect when we first were figuring out how the universe works.
The third law of thermodynamics, despite how fundamental it is, is one of those surprisingly limited aspects of classical physics. In saying that we can’t reach absolute zero without infinite time or infinite energy, it doesn’t fully take a fundamental aspect quantum physics—information theory—into account.
A principle of information theory called the Landauer principle states that there is a minimum, and finite, amount of energy that it takes to delete a piece of information. The catch here is that deleting information from a particle is the exact same thing as taking that particle to absolute zero. So, how is it possible that it takes a finite amount of energy to delete information and an infinite amount of energy to reach absolute zero, if those two things are the same?
It's not a total paradox—you could take an infinitely long time. But that doesn’t tell the whole story. The team discovered a key parameter that would get it done a whole lot faster—complexity. It turns out that if you have complete, infinite control over an infinitely complex system, you can bring fully delete information from a quantum particle without the need for infinite energy or infinite time.
Now, is infinite complexity with infinite control more achievable than infinite time or infinite energy? No. We’re still dealing with infinities here.
But this discovery does emphasize known limitations in the functionality of quantum computers. Namely, once we start saving information on those things, we’re never going to be able to fully scrub the information from the quantum bits (known as qubits) making up our information storage centers.
According to experts, that’s not going to present a practical issue. Machines that operate absolutely perfectly already don’t exist, so there’s no reason to hold quantum computers to an unreachable standard. But it does teach us a bit more about exactly what building and operating these futuristic machines is going to take.
When it comes to quantum, we’re just getting started.
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