IBM Breaks Ground in Quantum Computing with Verifiable Correctness

IBM has made significant strides in quantum computing by demonstrating a 'quantum advantage' with verifiable correctness for the first time. The concept of quantum advantage refers to the ability of a quantum computer to solve a problem faster than a classical supercomputer.

In 2019, Google announced that its quantum computer had performed a calculation in just 200 seconds that would take a classical supercomputer 10,000 years to complete. However, IBM countered by arguing that an existing classical machine could solve the exact same problem in 2.5 days with optimized algorithms and storage.

The ambiguity surrounding the concept of quantum advantage was resolved when a team from IBM and the University of Chicago announced an experiment that successfully combined verifiable correctness with surpassing the limits of classical computation. They used a 'spacetime code' to construct a circuit using only Clifford gates, which are easy to simulate classically, and then carefully grafted T gates into specific positions.

The team executed 2,415 logical two-qubit operations on a Heron processor, confirming that more than 28% of the results had faithfully completed the computation. The lower bound of fidelity was calculated to be 0.284 with a 95% confidence level.

While this method comes with a significant cost, requiring an 860-fold increase in runs due to error detection, it marks a crucial step towards practical quantum computation and verifiable correctness.