October 23, 2019

Google says it has reached quantum supremacy, but not everyone agrees

By Ellen Daniel

Google has shed light on its claims that it has reached quantum supremacy, but not everyone is in agreement.

The scientific paper, in which Google gives details of how it has developed and tested its quantum computer chip, was leaked last month on a Nasa website. It has now been officially published by Google in the journal Nature.

Named the Sycamore processor, the 54-qubit computer was built by Google and is the result of over a decade of work, representing a key milestone in the quest to make a fully-fledged quantum computer a reality.

Quantum computers are based on quantum bits, also known as qubits, which can be made from a single electron. Unlike ordinary transistors, used in other computers, which can be either “0” or “1,” qubits can be both “0” and “1” at the same time, meaning they can be in different states at the same time. This means that they can perform multiple calculations simultaneously, and so complete them far faster than even supercomputers.

Quantum supremacy refers to a task that a conventional computer would not be able to perform. According to the report, the computer takes 200 seconds to “sample one instance of a quantum circuit a million times” when performing a calculation to determine the randomness of a sequence of numbers, which would take the most powerful supercomputer 10,000 years. Google has described this as “a milestone on the path to full-scale quantum computing”, achieving quantum supremacy.

Google quantum supremacy challenged by IBM

Since they emerged last month, the scientific community has paid close attention to Google’s quantum computing claims. In a blog post written by Edwin Pednault, John Gunnels, and Jay Gambetta, IBM has said that the task performed by the quantum computer could, in fact, be done by a supercomputer in 2.5 days, meaning that quantum supremacy has not been achieved.

The blog post said that “the term ‘quantum supremacy’ is being broadly misinterpreted and causing ever-growing amounts of confusion, we urge the community to treat claims that, for the first time, a quantum computer did something that a classical computer cannot with a large dose of scepticism due to the complicated nature of benchmarking an appropriate metric”.

Nonetheless, the ability to perform calculations at this speed has important implications for numerous fields such as medicine, physics and chemistry. IBM has also invested heavily in this area, announcing that it plans to launch its own 53-qbit quantum computer soon.

Read More: Preparing for quantum computing’s devastating impact on cybersecurity.