Quantum Supremacy
Quantum supremacy refers to the potential of quantum computers to solve problems that classical computers practically cannot, within a reasonable timeframe. This concept was first formally proposed in a 2011 paper by John Preskill, a professor at the California Institute of Technology (Caltech).
History
- In 2011, John Preskill coined the term "quantum supremacy" to describe the point where quantum computers could outperform classical computers on specific tasks.
- The term gained significant attention in 2019 when Google announced that its Sycamore processor had achieved quantum supremacy by performing a specific computational task in 200 seconds that would take the world's most powerful supercomputer approximately 10,000 years to complete. This claim was published in the journal Nature.
- Following Google's claim, IBM contested the assertion, suggesting that with better algorithms and hardware, the classical computer could perform the same task in less time, although still significantly longer than the quantum computer.
Context
Quantum supremacy is not about a quantum computer being universally faster than a classical computer for all tasks, but rather demonstrating a computational advantage in at least one specific, well-defined problem. Here are some key points:
- Random Circuit Sampling: The task Google used to demonstrate quantum supremacy involved generating random quantum circuits and measuring the output distribution. This task is believed to be hard for classical computers due to the exponential growth in the number of variables involved.
- Verification: One of the challenges in claiming quantum supremacy is verifying the results. Since the task is beyond the reach of classical computers, direct verification is not feasible. Instead, techniques like cross-entropy benchmarking or using a less powerful quantum circuit to check the results of a more complex one are used.
- Implications: Achieving quantum supremacy could have profound implications for fields like cryptography, material simulation, drug discovery, and optimization problems. However, it does not mean that quantum computers will replace classical computers for all tasks; rather, they would complement them.
- Controversy: The term "supremacy" has drawn criticism for its connotations, leading to discussions about alternative terms like "quantum advantage" which might be less controversial and more accurately describe the phenomenon.
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