As of 2026-03-02, the state of the art in quantum decryption has cracked a:

  • 22-bit RSA key
  • 6-bit elliptic curve key

https://forklog.com/en/quantum-computer-cracks-tiny-cryptographic-key

The IBM QC that cracked the 6-bit key uses 133 qubits.

Some new research suggests that RSA-2048 could be cracked with as "few" as 100,000 qubits.

https://www.newscientist.com/article/2516404-breaking-encryption-with-a-quantum-computer-just-got-10-times-easier/

(Paywall-free)

Such a machine...is not feasible to build any time soon.

So when your CISO or a vendor starts going off about "post-quantum" security, feel free to use this to remind them that we still have SMB1 in some places and Telnet in others. Plenty of work to do around the house.

Quantum Computer Cracks ‘Tiny’ Cryptographic Key | ForkLog

forklog.media

@mttaggart A followup on this one. Turns out that Shor needs so many qubits because it needs to compute x^r mod n for all r in range 1..n-1. Shor does this with quantum magic and lots of qubits.

The giant reduction in qubits for the claimed breakthrough is that they compute these classically and then load them up into the quantum computer. Of course that saves on qubits, but only at the expense of exponential running time. So, not actually a breakthrough, just more trickery.

@sten @mttaggart Trickery can be a breakthrough, too.