— Alexandr Gnezdilov Light Painting/Moment/Getty Images

We’ve searched the skies for alien signals in the form of radio waves and reflected light from massive orbiting structures. But physicists Gia Dvali (of the Max Planck Institute for Physics) and Zara Osmanov (of the Free University of Tblisi) say we should also be looking for neutrinos and bursts of radiation from tiny black holes spawned as alien supercomputers.

Dvali and Osmanov suggest, in a recent paper, that technologically-advanced aliens (if they’re out there) might use small black holes as hardware for their quantum computers. And with telescopes like IceCube, we might be able to detect the output of those alien computer programs.

They published their work in the International Journal of Astrobiology.

The Most Out-There Way to Look for Aliens Yet?

At the edge of a black hole, called the event horizon, physics can become extremely weird. No matter or light that falls into the event horizon can escape the black hole’s powerful gravity, and yet strange quantum physics along the event horizon cause the black hole to emit a faint glow, called Hawking radiation. If late physicist Stephen Hawking was correct, Hawking radiation is actually the black hole’s mass slowly evaporating.

What’s important about that, if you want to build a super-powerful quantum computer in space (and who doesn’t, right?), is that physicists are still arguing about whether Hawking radiation contains any information about the matter and light that fell into the black hole. If you toss a planet into the burning surface of a star, the light and heat that’s emitted afterward will carry some information about the planet’s mass and chemical makeup. But Hawking’s original idea about Hawking radiation suggested that it was more like burning up a dictionary: all the original information is technically there in the pile of ashes, but it’s so badly garbled that it may as well not be.

On the other hand, some physicists now argue that actually, Hawking radiation isn’t randomly garbled, irretrievable data. The properties of the Hawking radiation a black hole emits are actually related to the properties of the original matter or light that fell in – we just don’t know how to reverse the process. In other words, black holes are performing complicated computations on everything that falls in, and spitting out Hawking radiation as the processed output.

And Dvali and Osmanov, in their recent paper, suggest that hypothetical alien civilizations might use black holes as the basis of quantum computer hardware. In a line right out of a sci-fi version of Jane Austen, the authors write, “It is thereby expected that all sufficiently advanced civilizations ultimately employ black holes in their quantum computers.”

More importantly, Dvali and Osmanov suggest we might be able to spot the data output from those black hole hard-drives – or the light of the high-powered particle accelerators used to manufacture them. We just need to look.

How It Works – As Far as We Know

A typical computer codes information in ones and zeroes, which represent one of two possible states for a magnet, a switch, or an electrical charge. Each bit of information is written in one of these states. But a quantum computer stores information in a more complicated format, in units called qubits (short for “quantum bits”). A qubit represents the physical state of a subatomic particle, and it could be something like the polarization of a photon, the angular momentum (the speed and direction of spin) of an atom, or several other properties.

A qubit’s data can be one state or the other, but it can also be both at once, at least until you actually measure it (this is called quantum superposition, and it’s the principle behind the infamous Schrodinger’s Cat). That means quantum computers present information in the probability of a quantum state at a given moment.

Subatomic particles can be entangled with each other, so the quantum state of one particle depends on the state of another particle (which may or may not actually be nearby). That complicates the possible states of any one qubit. And all of that adds up to qubits being able to store more data, and do more calculations with it, than regular bits.

In other words, quantum computers can do more complicated calculations much more quickly than regular computers – in theory. Computer scientists here on Earth are still working out the best way to design and use quantum computers so they’re as useful as theory says they should be. But Dvali and Osmanov say the odds are good that more advanced civilizations, on older planets around older stars, would have it figured out.

“Since our Solar System is relatively young, it is reasonable to assume that more highly evolved inhabitants of older star systems are already using sophisticated quantum technologies,” they write.

Black Holes as Computer Hardware

According to Dvali and Osmanov, a black hole would be an even faster quantum computer than one made of normal matter. That’s because all the matter in a black hole is squished into a single point, or singularity. Because the black hole is so dense, it takes almost no time for light – and information about qubits – to cross from one side of the black hole to the other.

In other words, a black hole should a super fast, super efficient piece of computer hardware, as long as the operator avoids falling in.

But how would you program one? The details are still very fuzzy, but coding for a black hole quantum computer would probably involve some version of manipulating the quantum states of matter – or maybe light photons – and then tossing them into a black hole. What emerges as Hawking radiation will be the output of those calculations.

“We shall not attempt to make any assumptions about the software used by the advanced extraterrestrial intelligence,” write Dvali and Osmanov. “The power of programming and the sophistication of their algorithms are most likely way beyond our imagination.”

In other words, we have no idea how to program a black hole quantum computer, but advanced enough alien civilizations might – and the idea that a black hole could make good hardware for one is worth considering, according to Dvali and Osmanov.

How to Spot Quantum-Computing Aliens

Smaller black holes should have faster processing speeds, so these hypothetical advanced aliens may want to create tiny black holes to do their computing. And small black holes (ones with less mass packed into them) emit more Hawking radiation. That also means we could, potentially, detect the final bursts of high-energy radiation from a vanishing black hole – or one finishing its computations.

To create those tiny black holes, they’d need to smash matter together in high-energy particle accelerators. Black holes small enough to be useful computers would have masses of a few hundred billion kilograms, at most (that’s a very tiny fraction of Earth’s mass, never mind the mass of a star), and physicists don’t know of any way for such a small black hole to form in nature. So finding one would mean discovering either new physics or quantum-computing aliens, according to Dvali and Osmanov.

If Dvali and Osmanov are right, the possibility gives us two things to look for: the last bright burst of Hawking radiation from a small black hole evaporating at the end of its life, or radiation and high-energy particles from the accelerators used to produce this cosmic computing hardware.

Detectors like IceCube should be sensitive enough to spot some of signatures, say Dvali and Osmanov. We probably won’t be able to make heads or tails out of the aliens’ data, but at least we’ll have some indication that they’re out there. And that they’re giant computer nerds.

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