Quantum supremacy refers to the point at which a quantum computer can perform a calculation that is practically impossible for any classical computer to achieve within a reasonable amount of time. This concept highlights the unique capabilities of quantum systems, which harness the principles of quantum mechanics, such as superposition and entanglement, to solve complex problems more efficiently. In simpler terms, once quantum computers can outperform classical computers on specific tasks, this milestone is considered reached.
As of now, claims of achieving quantum supremacy have been made, notably by Google in 2019. In their experiment, Google’s quantum processor, named Sycamore, reportedly completed a specific task in about 200 seconds that would take the most advanced classical supercomputers thousands of years to finish. This experiment was designed to demonstrate quantum advantage by solving a problem that doesn't have significant practical applications but showcases the potential of quantum computing. However, this claim did attract skepticism within the scientific community, as some researchers argued that the specific task Google chose could be executed differently on classical systems, albeit less efficiently.
The ongoing discussions about quantum supremacy indicate that the field is still in its early stages. While some companies and research institutions are making progress toward scalable quantum computers, the practical applications of quantum supremacy remain limited. The focus is now shifting towards creating more robust quantum systems that can solve real-world problems, such as optimization and drug discovery. Thus, while quantum supremacy may have been achieved in a controlled setting, the broader capability and reliability of quantum computing for significant tasks are still under active research and development.