Quantum supremacy still not a given

Nature published Google’s groundbreaking results on a 54-qubit quantum computer in October, effectively declaring that quantum supremacy had been achieved. A few weeks later, however, a team of researchers from Irig and the US-based Flatiron Institute produced very similar calculations on a common laptop computer.

Google did reach an impressive milestone when it successfully operated a “real” quantum machine with 54 physical qubits. The tech giant’s researchers performed a calculation that even the best conventional machine would have taken 10,000 years to do, in just 200 seconds. One thing the research did not factor in, however, is this: Because of the quantum computer’s inherent precision and decoherence problems, the error rate  of each operation is 1%.

Multiplying the number of qubits should not be the end goal

The Irig-Flatiron Instituteresearchers posited that Google’s machine did not even come close to utilizing the full power of quantum. They then used quantum-state compression algorithms to simulate the Google machine’s actual operation…on a regular consumer-grade computer! In just a few hours they completed the same calculations that the Google researchers said would take decades.

Their findings refocus attention on the real issue, which is not necessarily to build machines with more qubits, but rather to improve reliability—something that still raises serious theoretical and practical challenges. Another added bonus of the research is that Irig developed a tool unlike any other for evaluating the performance of current and future quantum computers. Irig has obtained several grants for further research on this topic.

Contact: xavier.waintal@cea.fr