Quantum supremacy is a significant milestone in the field of quantum computing. It refers to the point at which a quantum computer can solve a computational problem that is infeasible for classical computers to solve within a reasonable amount of time. In other words, a quantum computer demonstrates its superiority by performing a computation that is beyond the capabilities of the most powerful classical computers.
The concept of quantum supremacy was first introduced by John Preskill in 2012. Achieving quantum supremacy is a key step towards demonstrating the potential of quantum computers and their ability to outperform classical computers in specific tasks.
To achieve quantum supremacy, a quantum computer must be able to perform a computation that exhibits a quantum advantage over classical computation. This is typically demonstrated through the execution of a carefully designed quantum algorithm, known as a quantum supremacy experiment.
In a quantum supremacy experiment, a quantum computer is tasked with solving a specific problem or executing a random quantum circuit that is designed to be challenging for classical computers. The key aspect is that the problem or circuit is carefully constructed to leverage the quantum computer's strengths while making it difficult for classical algorithms to efficiently simulate or solve.
The main goal of a quantum supremacy experiment is to demonstrate that the quantum computer can solve the problem or execute the circuit with a level of efficiency or computational speed that surpasses what classical computers can achieve. This serves as evidence of the quantum computer's computational superiority and establishes the achievement of quantum supremacy.
In 2019, Google's research team claimed to have achieved quantum supremacy by performing a computation that would take classical supercomputers an impractical amount of time to complete. They used a 53-qubit quantum computer called Sycamore to perform a specific random circuit sampling task.
It's worth noting that quantum supremacy is a specific milestone and does not imply that quantum computers can solve all computational problems more efficiently than classical computers. There are still significant challenges in scaling up quantum computers, improving qubit coherence and error rates, and developing quantum algorithms that can solve practical problems with real-world impact.