Ahead of Singapore's Milestone Demo, the Real Advance Is Boringly Reliable Qubits

SINGAPORE — In the days before the Singapore Institute is expected to run a million-qubit processor over the Q-Net backbone, the physicists closest to the work keep redirecting attention from the number to the noise. "A million qubits that constantly make errors is a very expensive space heater," said Dr. Wei-Lin Tan, the Institute's quantum communicator, ahead of the forthcoming demonstration. The advance she wants credited is error correction: binding thousands of fragile physical qubits into a handful of stable logical ones that survive long enough to compute. Two years ago it took roughly three thousand physical qubits to hold a single logical qubit steady through a full calculation, Tan said; her group is now near a thousand. The near-term payoff is unglamorous: materials chemistry, protein folding, climate models that resolve a coastline instead of a smudge. The Institute plans to report that physical-to-logical ratio beside the headline count, and to publish the run's full error log the same week.