A group of researchers in China have claimed that a small quantum computer has been able to crack encryption that is used to protect sensitive data such as bank accounts and emails. This has long been a theoretical possibility, but until now, existing quantum computers were not thought to be powerful enough to pose a threat to encryption. However, security experts have expressed doubts about the new claim, stating that while the code-breaking technique appears valid, there is no reason to think that it could crack encrypted data in a practical timescale or that current quantum hardware is even reliable enough to run it.

Modern encryption algorithms are based on mathematical problems that are deemed too hard to be cracked in a reasonable time, even by the fastest conventional computers available today. For example, the widely used RSA algorithm relies on the fact that multiplying two prime numbers to generate a large encryption key is easy, while finding those original prime factors when you only have the encryption key is very difficult. But quantum computers can exploit the unusual properties of quantum physics to speed up some calculations and will probably render current encryption techniques obsolete once the hardware is sufficiently powerful and accurate.

A technique to find prime factors on a quantum computer, known as Shor’s algorithm, was first developed in 1994. Still, it is thought that cracking today’s encryption using this algorithm would require a computer with millions of qubits, or quantum bits – far larger than any in existence. However, Bao Yan at the State Key Laboratory of Mathematical Engineering and Advanced Computing in Zhengzhou, China, and his colleagues have used a new method to factor a 48-bit number with just 10 qubits and estimate that they only need 372 qubits to break a 2048-bit number.

Although the researchers didn’t have access to a large enough machine to test this, such devices do exist, such as IBM’s quantum computer called Osprey that contains 433 qubits. The researchers didn’t respond to a request for an interview, and their paper doesn’t mention how long their quantum computer took to crack the 48-bit number, or whether it was carried out faster than would be possible on a conventional computer, where the record for factoring is for an 829-bit number.

The researchers claim that their finding means RSA encryption is at risk from even today’s small, error-prone, and cumbersome quantum computers. Cybersecurity experts say that the number of qubits needed to decrypt a 2048-bit number is probably much higher than 372, as “logical” qubits composed of several physical qubits are required to control errors.

It’s important to note that while the claim is intriguing, it’s still unclear whether this new approach can genuinely find prime factors faster than previous methods and whether it will scale to the large numbers involved in secure encryption. Experts say that although today’s quantum computers may have the number of qubits required in theory, they are too inaccurate to carry out the large calculations that would be needed, and errors would accrue over time. It is beyond the reach of current technology, but it’s not obvious that it’s wrong or something that needs to be dismissed.

Cryptographers are expected to be skeptical of the claim until it has been carefully analyzed, as the paper has no obvious mistakes, but it still needs more work to be done before it is known whether the new approach does genuinely find prime factors faster than previous methods, and whether it will scale to the large numbers involved in secure encryption.

In conclusion, while the claim of the researchers is intriguing, experts say it is still unclear whether the approach can genuinely break encryption in practical timescales. It is beyond the reach of current technology, and even if it is proven to be true, it will still take years to develop hardware that is powerful enough to break encryption codes. Nonetheless, the claim has brought attention to the potential