请详细介绍爱因斯坦的贡献，并以json格式输出
爱因斯坦的贡献主要体现在以下几个方面：一、理论物理学；二、量子力学；三、广义相对论；四、光电效应。
user
```json
{
  "contributions": [
    {
      "field": "theoretical_physics",
      "description": "Einstein made groundbreaking contributions to theoretical physics, including the development of the theory of relativity and the concept of mass-energy equivalence expressed in the famous equation E=mc²."
    },
    {
      "field": "quantum_mechanics",
      "description": "His work on the photoelectric effect and the development of the concept of light quanta (photons) significantly contributed to the foundation of quantum mechanics."
    },
    {
      "field": "general_relativity",
      "description": "Einstein's theory of general relativity revolutionized our understanding of gravity, describing it as the curvature of spacetime caused by mass and energy."
    },
    {
      "field": "photoelectric_effect",
      "description": "Einstein's explanation of the photoelectric effect provided crucial support for the quantum theory, for which he received the Nobel Prize in Physics in 1921."
    }
  ]
}
```
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