Independent notes on quantum hardware, error correction, software, and the gap between a demo and a machine.

Four questions that decide whether this field has actually arrived. Most answers are still no, and saying so plainly is the point of the board. Last reviewed 24 September 2026.

• Early Stable, repeated error correction below threshold
• Early Logical qubits with useful operations
• Not yet Advantage on a scientific or industrial problem someone actually has
• Not yet Fault-tolerant machine at useful scale

1. A physical qubit is not a computer

   Qubit count is the number a manufacturer can most easily make go up, and the number that tells you least. Here is what the other numbers are, and why errors compound faster than registers grow.

2. What a logical qubit actually is

   The word “logical qubit” is now used for at least four different things, only one of which is the thing that matters. This is how to tell which one an announcement means.

3. How to read a quantum claim

   A procedure for taking any quantum announcement apart: find the number, find the comparison, find the conditions, and find out who checked. Most claims fail before the third step.