### Qubit-land is a short trip away.

"Is it heads or tails?" I ask after spinning a coin on a table. "What?" you'd probably ask, because my query isn't very clear. Before settling on a side, the coin is essentially both alternatives at the same time. Consider this perplexing coin to be "superposed."

You can't restore the exact state of limbo if you interrupt its superposition to investigate its fate — that is, stop the coin spinning. Superposition is irreversibly broken once it is broken.

Let's change the scenario so that two coins spin adjacent to each other. I've added a condition this time: If coin A lands on heads, so will coin B. In a sense, these coins have become intertwined. Each

Let's change the scenario so that two coins are spinning adjacent to each other. I've added a condition this time: if coin A lands on heads, so will coin B. These coins are now, in a sense, interconnected. The superposition of each coin is "entangled" with the superposition of the other.

Changes to coin A's superposition have an immediate impact on coin B's. Even if only coin A stops spinning, you acquire information about coin B, breaking its superposition as well. Even if the coins are on opposite sides of the universe, this holds true.

Okay, you're probably thinking: These analogies are somewhat dependent on the observer's thoughts. You are correct. That is, however, due to the fact that we are discussing currencies. These things happen physically with quantum particles like electrons and photons.

Superposition determines the state of a bit in the quantum computing universe. Classical bits are either 0 or 1, while qubits, which are made up of quantum particles, can be in superposition — that is, they can be both 0 and 1. The most crucial thing is that they retrieve data while in that state.

Qubits, as you might expect, race through calculations at unfathomable speeds, testing multiple iterations at once and entangling with other qubits to relay data instantly. That's the gist of it.

For perspective, Google and IBM quantum computers use superconducting quantum technology to equally distribute qubits on a grid. Qubits that are close together can entangle and exchange information. Webber's startup focuses on trapped ion circuitry, which allows qubits to freely travel about a grid and interact. More qubits, in any case, equals exponentially more processing power.

But, in order to take advantage of bitcoin's vulnerability window, how many of these qubits must be in sync?

### The challenge has been accepted: hack bitcoin.

So far, here's what we know: Bitcoin transactions are vulnerable to quantum computers for a limited period of time, but not to conventional computers or people. This is because quantum systems are densely packed with qubits, which fire at speeds that the human brain can hardly fathom.

Webber used external research to figure out how many qubits are required to get through that window, and he came up with some accurate estimates. But keep in mind the delicate nature of qubits. If something goes wrong in a quantum computer, superposition is disrupted, and all of the valuable quantum data is lost for good. And then things start to go wrong.

Quantum programmers do something fairly simple to avoid this calamity. They simply employ more qubits. Quantum error correction is the term for it.

To increase the probability of right data, they throw an army of qubits at every computation for the sake of simplification. It'd be reasonable to say that if 9/10 qubits supplied the same solution, it's correct.

"It's something like 1,000 physical qubits for one relatively high-quality, logical qubit — it's not perfect, but it's good," Webber said. To achieve a final answer, he increased his initial estimate by 1,000.

To hack bitcoin in one hour, you'd need around 317 million qubits. "It would just be a greater number" if you're looking at a 10-minute span, he said. "I'm guessing six times more."

"It requires less qubits overall if you want to break it more slowly," Webber explained, "so something like 13 million to break it in one day."

"Look at the movement of classical computing from vacuum tubes of 10 bits, or however many they had early on, to the extremes that we have now," Webber encourages, despite the fact that we're still a long way from a 13-million-qubit processor.

"Quantum computing will undoubtedly undergo a similar transformation."

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