Quantum computing company PsiQuantum has begun building a supersized quantum computing facility, reigniting debate that Bitcoin's cryptographic security could be threatened.

On March 6, blockchain media outlet Cointelegraph reported that PsiQuantum co-founder Terry Rudolph said at the 'Quantum Bitcoin Summit' held last July that there were no plans to use a quantum computer to break Bitcoin's cryptography. "In a company where hundreds of people work, it is impossible to hide doing something like this," he said.

But the scale of the project PsiQuantum is pursuing is heightening tensions in the industry. The company is building a 1 million-qubit quantum computer facility in Chicago, far larger than quantum computers developed so far.

PsiQuantum co-founder Peter Shadbolt on March 5 posted photos of the construction site on X, formerly Twitter, and said about 500 tons of steel structures were installed in six days. The facility is designed to house an "error-corrected quantum computer" that can operate even when errors occur.

Earlier, PsiQuantum announced in September last year that it raised about $1 billion in funding to build the facility in cooperation with chipmaker Nvidia. The company said the completed facility will have the computing power of 1 million qubits, equivalent to billions of conventional computers, and explained there is commercial potential to support next-generation artificial intelligence supercomputers.

But the Bitcoin community has long raised concerns that quantum computing could threaten Bitcoin's cryptographic system in the long term. Some argue the entire Bitcoin network, worth about $1.4 trillion, could be at risk.

In contrast, Adam Back (아담 백), chief executive of Blockstream, countered that quantum computers will not pose a practical threat to Bitcoin for at least 10 years.

Bitcoin developers are reported to be discussing the need for a hard fork to respond to quantum attacks in preparation for such possibilities.

In particular, what is seen as most vulnerable to a quantum attack is unspent transaction output (UTXO) wallets, meaning early bitcoins stored in addresses that have never been used. Many of these are linked to wallets created when Bitcoin was first generated.

Views differ on the computing power needed for a quantum computer to break cryptography. A recently published scientific paper claimed about 100,000 qubits would be needed to decrypt a 2,048-bit encryption key. For reference, Bitcoin uses a 256-bit encryption key.

The largest quantum computer disclosed so far is a 6,100-qubit system developed by the California Institute of Technology, showing a substantial gap still exists between the theoretical threat and reality.

There is also analysis that the amount of Bitcoin actually vulnerable to a quantum attack is limited. Crypto asset manager CoinShares in a February report assessed that about 10,230 bitcoins, worth about $728 million, have quantum vulnerability and said this is "only at the level of everyday transactions."

As quantum computing technology advances rapidly, whether Bitcoin's security will actually come under threat remains a matter of debate.

Time to build really big quantum computers. Five hundred tons of steel up in six days. Cryoplant delivery date breathing down our neck. Grateful to the many hundreds of people locked in to this mission pic.twitter.com/eqSwsESusK