April 19, 2026
This week, Google presented a paper outlining how a quantum computer could theoretically within nine minutes bitcoin could derive private key. This has consequences not only for Bitcoin, but also for Ethereum, other tokens, private couches and possibly even the entire world.
Quantum computing cannot be compared to a faster version of a regular computer. It is not about a more powerful chip or a larger server farm; it concerns a fundamentally different type of machine that differs at the atomic level.
A quantum computer starts with a very cold, small loop of metal, where particles behave in ways unknown under normal conditions on Earth, and which slightly distort our interpretation of the basic rules of physics. Fate-reading what this means physically is the difference between reading about the quantum threat and actually understanding it.
Regular computers store information as bits, in which each bit is either 0 or 1. A bit acts as an extremely small switch, which is physically a transistor on a chip — microscopic gates that either let electricity through (1) or not (0). Every photo, every bitcoin transaction, every letter you have ever typed is stored as patterns of these switches being on or off. There is nothing mysterious about a bit; it is a physical object in one of two clear states.
Every calculation simply consists of rearranging these 0s and 1s at lightning speed. A modern chip can perform billions of calculations per second, but this still happens one by one, in sequence.
Quantum computers use so-called qubits instead of bits. A qubit can be 0, 1, or — and this is the bizarre part — both at the same time!
This is possible because a qubit is a completely different type of physical object. The most common version, which is also used by Google, is a small loop of superconducting metal cooled to about 0,015 degrees above absolute zero; colder than space, but on Earth.
At that temperature, electricity flows through the loop without any resistance, and the current is in a quantum state. In the superconducting loop, the current can flow clockwise (let's call 0) or counterclockwise (let's call 1). But on a quantum scale, the current does not have to choose one direction; it flows in both directions simultaneously.
Remember that this is not a matter of quickly switching between the two; the current is measurable, experimental, and verifiable in both states simultaneously.
Clear so far? Great, because now it gets really weird, as the physics behind how it works isn't immediately intuitive and isn't meant to be.
Everything one encounters in daily life obeys classical physics, which assumes that things are in one place at one time. But particles do not behave that way at the subatomic level.
An electron has no definite position until you look at it. A photon has no definite polarization until you measure it. A current in a superconducting loop does not appear to flow in one particular direction until you force it to do so.
The reason we do not experience this in our daily lives is decoherence. When a quantum system interacts with its environment—air molecules, heat, vibrations, and light—the superposition falls apart almost immediately.
A football cannot be in two places at the same time because, in every nanosecond, it interacts with trillions of air molecules, dust, sound, heat, gravity, and so on. But when you isolate a small current in a near-absolute zero vacuum and protect it from any possible disturbance, the quantum behavior persists long enough to perform calculations.
That is why quantum computers are so difficult to build. People design physical environments in which the laws of nature that normally prevent the occurrence of these kinds of phenomena are held back for exactly long enough to perform a calculation.
Google's machines operate in diluted refrigerators the size of enormous rooms, colder than anything in the natural universe, surrounded by layers of shielding against electromagnetic noise, vibrations, and thermal radiation.
And even then, the qubits are vulnerable. They constantly lose their quantum state, which is why 'error recovery' is a dominant topic in discussions about scaling up.
Quantum computing is therefore not a faster version of classical computing. It uses a different set of laws of nature that apply only to extremely small scales, extremely low temperatures, and extremely short timeframes.
If we explore further: two regular bits can be in one of four states (00, 01, 10, 11), but only one at a time (since the current can flow in only one direction). Two qubits can represent all four of these states simultaneously, because the current flows in all directions at the same time.
Three qubits represent eight states. Ten qubits represent 1.024. Fifty qubits represent more than a quadrillion. The number of possible states doubles with each added qubit. This explains the exponential scalability of quantum computers.
A second important concept is what we call quantum entanglement. When two qubits are entangled, an observer immediately knows something about the other the moment the first is measured, regardless of the distance between them. This allows a quantum computer to coordinate between all those simultaneous states in a way that ordinary parallel computers cannot.
These quantum computers are designed so that incorrect answers cancel each other out (like overlapping waves that flatten each other) and correct answers reinforce each other (like waves that build up higher). At the end of the calculation, the probability of measuring the correct answer is highest.
It is therefore not merely brute force; it is a fundamentally different approach to calculations — one that enables nature to explore an exponentially large space of possibilities and that ultimately brings forward the correct answer through physics rather than logic.
This mind-boggling physics makes it a solid ninety for encryption.
The mathematics that protects Bitcoin is based on the assumption that verifying every possible key would take longer than the age of the universe.
But a quantum computer does not check every key; it explores them all simultaneously and uses interference to bring the right one to the surface.
This has everything to do with Bitcoin. From private color key to public key is a matter of milliseconds, but the reverse – from public key back to private color – would take a classical computer a million years, or even longer than the age of the universe. That asymmetry is the only proof that a person owns their bitcoins.
A quantum computer running an algorithm called Shor's can break that trap in the reverse direction. Google's paper this week showed that this can be done with far fewer resources than previously estimated, and within a timeframe racing against Bitcoin's own block confirmations.
This is the reason why the threat of quantum computers capable of breaking blockchain encryption raises genuine concern.
How this attack works step by step, what the specific changes in Google's paper are, and what it means for the 6,9 million bitcoins that have already been exposed, is the subject of the next piece in this series.
What are the main differences between classical computers and quantum computers?
Classical computers use bits, which are either 0 or 1, while quantum computers use qubits, which can be both 0 and 1 simultaneously. This enables quantum computers to process exponentially more information at the same time.
Why do quantum computers pose a threat to blockchain technologies?
Quantum computers can break the encryption that secures blockchain technologies like Bitcoin by simultaneously exploring all possible keys, rather than having to verify them one by one. This can undermine the entire system of ownership and security.
What is the significance of Google's recent paper on quantum computers?
The paper reveals that existing estimates regarding the resources required for quantum computers to break blockchain encryption are too optimistic. It demonstrates that these computers can effectively operate faster and with fewer resources, which increases the urgency of the problem.
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