在统计中,主成分分析(PCA)是一种通过最大化每个维度的方差来将较高维度空间中的数据投影到较低维度空间中的方法。给定二维,三维或更高维空间中的点集合,可以将“最佳拟合”线定义为最小化从点到线的平均平方距离的线。可以从垂直于第一条直线的方向类似地选择下一条最佳拟合线。重复此过程会产生一个正交的基础,其中数据的不同单个维度是不相关的。 这些基向量称为主成分。

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Quantum technology has the potential to revolutionize how we acquire and process experimental data to learn about the physical world. An experimental setup that transduces data from a physical system to a stable quantum memory, and processes that data using a quantum computer, could have significant advantages over conventional experiments in which the physical system is measured and the outcomes are processed using a classical computer. We prove that, in various tasks, quantum machines can learn from exponentially fewer experiments than those required in conventional experiments. The exponential advantage holds in predicting properties of physical systems, performing quantum principal component analysis on noisy states, and learning approximate models of physical dynamics. In some tasks, the quantum processing needed to achieve the exponential advantage can be modest; for example, one can simultaneously learn about many noncommuting observables by processing only two copies of the system. Conducting experiments with up to 40 superconducting qubits and 1300 quantum gates, we demonstrate that a substantial quantum advantage can be realized using today's relatively noisy quantum processors. Our results highlight how quantum technology can enable powerful new strategies to learn about nature.

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