(I-HLS) Scientists Craig Gidney at Google and Martin Ekerå at the KTH Royal Institute of Technology in Stockholm have found a more efficient way for quantum computers to perform the code-breaking calculations, reducing the resources they require by orders of magnitude. Their findings will concern governments, military and security organizations, banks, and anyone else who needs to secure data for 25 years or longer.
Yet quantum factoring is much harder in practice than might otherwise be expected. The reason is that noise becomes a significant problem for large quantum computers. And the best way currently to tackle noise is to use error-correcting codes that require significant extra qubits themselves.
Now Gidney and Ekerå have shown how a quantum computer could do the calculation with just 20 million qubits. Indeed, they show that such a device would take just eight hours to complete the calculation. “[As a result], the worst case estimate of how many qubits will be needed to factor 2048 bit RSA integers has dropped nearly two orders of magnitude,” they say. Their method focuses on a more efficient way to perform a mathematical process called modular exponentiation.

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