Everyone quotes qubit counts. Almost nobody quotes the one that matters.
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Hardware
Everyone quotes qubit counts. Almost nobody quotes the one that matters.
Around 300 physical qubits per logical qubit. That was the working estimate not long ago, and this year Microsoft and Quantinuum cut it roughly tenfold, reaching four logical qubits from 30 physical.
Key Takeaways
- Headline qubit counts are physical qubits, which are noisy. Logical qubits are the error-corrected ones that can do useful work.
- Microsoft and Quantinuum cut an estimate of 300 physical qubits per logical qubit roughly tenfold, reaching four logical from 30 physical.
- Google Willow showed logical error rates falling about 2.14 times for each increase in surface code lattice size, the first hardware evidence that fault tolerance scales as theory predicted.
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