Quantum theory is over 100 years old, but the arrival of fault-tolerant quantum computers (FTQC) seems far from near. Current quantum computers belong to the so-called NISQ-era which means "noisy intermediate scale quantum," a term coined by theoretical physicist John Preskill.
Preskill explains: "We now have quantum machines such that brute force simulation of what the quantum machine does is well beyond the reach of our most powerful existing conventional computers. But these machines are not error-corrected, and noise severely limits their computational power."
Detecting and correcting noise in quantum computers is a complicated matter. Qubits are delicate. Vibrations, temperature changes, electromagnetic waves, and unintentional interactions between qubits can cause errors in calculations.
Plus, there are many types of qubits being used today, ranging from the transmon qubit, (typically used) to fluxonium qubits, which includes a superinductor to help shield the qubit from environmental noise.
Has progress been made? Definitely. This year Google's Willow processor reduced the frequency of error bursts from happening once every ten seconds to once per hour.
However, Preskill explains:
"Whether suppression of error bursts via gap engineering will suffice for running deep quantum circuits in the future is not certain, but this progress is encouraging. And by the way, the origin of the error bursts seen every hour or so is not yet clearly understood, which reminds us that not only in superconducting processors, but in other modalities as well, we are likely to encounter mysterious and highly deleterious rare events that will need to be understood and mitigated."
As the world waits for highly advanced quantum computers capable of performing millions or billions or trillions of operations—or what Preskill describes as megaquop, gigaquop and teraquop machines—the race to achieve economic value from merging classical and quantum systems is steadily moving forward.
Note: Renowned physicist Michio Kaku says if a quantum computer ever gets hacked—to "shut the things down"—which sounds strikingly similar to Eric Schmidt's solution "unplug them immediately" —if AI agents ever start talking to each other in language we don't understand. [see article: "Probably Safe AI"]
"The only thing that can defeat a quantum computer is another quantum computer. So for example, polarization vector... If somebody tampers with that light beam, the polarization vector changes. Put all your secrets on one laser beam and watch that polarization vector! Once that polarization vector starts to tilt, then boom—shut the things down."
All Sources:
https://www.youtube.com/watch?v=3T0NaEj6wiE
https://www.nature.com/articles/s41586-024-07998-6
https://quantumfrontiers.com/2024/12/14/beyond-nisq-the-megaquop-machine/
https://preskill.caltech.edu/talks/Preskill-Q2B-2024.pdf
https://blog.google/technology/research/google-willow-quantum-chip
https://www.bnl.gov/quantumcenter/
https://www.ibm.com/quantum/technology
https://ece.princeton.edu/people/claire-gmachl
https://www.youtube.com/watch?v=3T0NaEj6wiE