For years, scientists believed that adding even one qubit (a unit of quantum information) to a black hole needed energy. This was based on the idea that a black hole’s entropy must increase with more information, which means it must gain energy. But a new study by Jonah Kudler-Flam and Geoff Penington changes that thinking. They found that quantum information can be teleported into a black hole without adding energy or increasing entropy. This works through a process called black hole decoherence, where “soft” radiation — very low-energy signals — carry information into the black hole. In their method, the qubit enters the black hole while a new pair of entangled particles (like Hawking radiation) is created. This keeps the total information balanced, so there's no violation of the laws of physics. The energy cost only shows up when information is erased from the outside — these are called zerobits. According to Landauer’s principle, erasing information always needs energy. But teleporting it, like in this case, does not. This discovery reshapes how we think about black holes — not as destroyers of information, but as part of a quantum communication system.
For years, physicists believed that putting new quantum information into a black hole — even just one qubit (the smallest unit of quantum information) — must come with an energy price. This idea was based on the famous Bekenstein-Hawking entropy theory, which says that black holes have entropy (a measure of information) and temperature (Hawking temperature). The common belief was that increasing a black hole’s information must also increase its entropy and therefore its energy.
However, a groundbreaking paper by Jonah Kudler-Flam and Geoff Penington challenges this old idea. They explain how quantum information can be teleported into a black hole with almost no energy cost at all. Their work is based on a recent discovery called black hole decoherence.
Let’s explore what this means — and why it’s such a big deal in our understanding of black holes and the universe.
The Old Belief: Information Costs Energy
According to traditional theories, if you try to add a qubit into a black hole, you must add enough energy to increase the black hole’s entropy. A basic explanation goes like this:
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Imagine a black hole is already maximally entangled with a reference system (call it R).
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You now send in a qubit that is entangled with another reference system (call it X).
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The total entanglement must still be preserved, because quantum mechanics says information can’t be lost (this is called unitarity).
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For the black hole to hold all this entanglement, it needs to increase its entropy by one unit.
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That means it needs to gain a certain amount of energy, specifically:
ΔE ≥ TH × log(2)
where TH is the black hole’s Hawking temperature.
This reasoning is closely tied to the generalized second law of thermodynamics (GSL), which says the total entropy of the black hole plus the outside world can never decrease.
Why This Assumption Is Flawed
Although this logic seems solid, it isn’t airtight. It overlooks some subtleties in how quantum information and black holes interact.
In particular, Kudler-Flam and Penington show that while the laws like the GSL and Bekenstein bound are still valid, they don’t actually force a black hole to increase its energy every time new information is added.
Here’s the twist: it turns out that we can teleport information into a black hole without changing its energy or entropy — if we do it the right way.
The Key Idea: Black Hole Decoherence
To understand this, we need to introduce the idea of decoherence near black holes, explored in a thought experiment by Danielson, Satishchandran, and Wald (DSW).
Imagine an experiment:
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A scientist named Alice sends a particle through a Stern-Gerlach device, which separates the particle's quantum paths based on its spin.
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This creates a quantum state that looks like:
|Ψ⟩ = 1/√2 (|↑⟩ |ψ↑⟩ + |↓⟩ |ψ↓⟩)
Here, the particle is in a superposition of two paths, and each path creates a different electromagnetic field (ψ↑ and ψ↓).
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Normally, in flat space (with no black hole), these paths can be recombined after some time, and the quantum coherence is preserved.
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But near a black hole, something strange happens.
Due to the presence of a black hole’s event horizon, the soft, low-energy radiation from these paths carries away “which-path” information into the black hole. This process leads to decoherence — the loss of quantum coherence — because the black hole now holds some of the information about the particle's path.
And here’s the crucial point: this decoherence does not require any hard radiation or significant energy. In the adiabatic (gentle and slow) limit, the energy added to the black hole is essentially zero.
How Does This Allow Teleportation?
Kudler-Flam and Penington took this insight further.
They designed a protocol using this decoherence effect to teleport a qubit into a black hole, without adding energy. Here's how it works:
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A qubit is entangled with a system outside the black hole.
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By using a gentle interaction (like Alice’s experiment), soft radiation carries this quantum information into the black hole.
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At the same time, a Bell pair of entangled particles is created — one inside and one outside the black hole. This Bell pair acts like a synthetic Hawking radiation.
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This process maintains the unitarity of quantum mechanics and does not violate the generalized second law.
The qubit effectively disappears from the outside world and reappears inside the black hole — with no net energy cost.
But Wait — Doesn’t That Violate Physics?
No, it doesn’t.
The key idea is that the cost of sending information into a black hole is not about the information itself, but about the erasure of information from the outside world.
This idea comes from Landauer’s principle, which says that erasing information always has an energy cost. If you don’t erase information — if you just move it — you don’t have to pay energy.
In this protocol:
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The qubit is teleported (not erased).
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The entanglement it had outside is replaced with a new entanglement (the Bell pair).
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So, the total entropy and energy remain balanced.
The only time an energy cost appears is when you intentionally erase the information from the outside — these are called "zerobits."
In other words:
Energy is required to destroy information, not to move it.
What Are Zerobits?
“Zerobits” is a term coined in this context to mean the coherent erasure of information. When you send zerobits into a black hole, you’re cleaning up or deleting quantum data from the outside.
This is where the real energy cost shows up. According to Landauer's principle, deleting one bit of information requires at least kT × log(2) amount of energy (in thermodynamics). In black holes, the same rule applies in a quantum gravity version.
So, if you try to remove noise or erase knowledge from the outside world, the black hole must pay the energy cost. But if you're simply moving a qubit in — with its correlations preserved — you can get away with zero energy.
A New View of Quantum Communication
This work shifts how we think about communication with black holes. It suggests that black holes can be part of a quantum communication channel, where information flows without needing massive energy input — as long as we respect the rules of entanglement and coherence.
Think of it like whispering a secret into a cosmic void — and if you do it carefully, the void hears you without needing to shout or burn energy.
This also provides a sharper understanding of how Hawking radiation might preserve information — something that has puzzled physicists for decades (known as the black hole information paradox).
Why This Matters
This research has deep implications for physics and our understanding of the universe:
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Solves a Key Puzzle: It helps resolve the conflict between quantum mechanics and black hole thermodynamics.
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Supports Unitarity: It shows how quantum information can be preserved even when falling into a black hole.
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Introduces New Physics Tools: It connects ideas from quantum computing (like entanglement and resource theories) with gravitational physics.
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Opens New Research Avenues: It could influence how we think about quantum gravity, spacetime structure, and even future technologies based on black holes.
Conclusion: Rethinking the Black Hole’s Role
Black holes were once seen as ultimate destroyers — anything that enters is lost forever. But modern physics, especially with insights like these, shows that black holes might be more like cosmic data hubs, handling information in subtle and surprising ways.
Thanks to the work of Kudler-Flam, Penington, and others, we now see that information doesn’t always need to burn its way into a black hole. With the right quantum tricks, it can simply slip in — quietly, cleanly, and without costing the universe extra energy.
It’s a remarkable reminder that in the quantum world, even the darkest objects in the universe have secrets to share — if we learn how to listen.
Reference: Jonah Kudler-Flam, Geoff Penington, "It costs nothing to teleport information into a black hole", Arxiv, 2025. https://arxiv.org/abs/2504.01058
Technical Terms
1. Qubit
The smallest unit of quantum information (like a "bit" in classical computing, but can be in multiple states at once).
2. Black Hole
A region in space where gravity is so strong that nothing, not even light, can escape from it.
3. Entropy
A measure of information or disorder in a system. More entropy = more information or randomness.
4. Hawking Temperature (TH)
The temperature of a black hole due to quantum effects, named after Stephen Hawking. It shows black holes can slowly give off heat (Hawking radiation).
5. Bekenstein-Hawking Entropy
The amount of information (entropy) stored in a black hole, which is related to the surface area of its event horizon.
6. Generalized Second Law (GSL)
The total entropy of the black hole plus the outside world should never decrease — it's like a rule to protect information.
7. Unitarity
A rule in quantum mechanics that says information cannot be lost; it must always be preserved.
8. Teleportation (in quantum physics)
Sending information from one place to another using entanglement, without moving the physical particle itself.
9. Decoherence
When a quantum system loses its "quantum-ness" (like superposition or entanglement) and starts behaving like a normal classical system.
10. Stern-Gerlach Experiment
A classic experiment that splits particles based on their spin, showing how quantum states can be separated.
11. Wavefunction
A math description of a quantum system — it tells you everything you can know about a particle.
12. Soft Radiation
Very low-energy radiation (like a gentle whisper of energy) that carries subtle information.
13. Bell Pair
Two particles that are perfectly entangled — if you know one, you instantly know the other, no matter the distance.
14. Landauer’s Principle
A principle that says erasing information always needs a minimum amount of energy.
15. Zerobits
A term used here to mean bits of information that are erased from the outside world. Erasing them costs energy.
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