请您简要说明量子计算和经典计算的主要区别和它们可能带来的影响，请使用json格式回答，并包含"quantum_advantage", "qubit"和"classical_bit"三个关键词。
user
```json
{
  "quantum_computing": {
    "main_differences": [
      {"aspect": "basic_unit", "quantum": "qubit", "classical": "classical_bit"},
      {"aspect": "parallelism", "quantum": "exponential", "classical": "linear"}
    ],
    "potential_impacts": {
      "areas_affected": ["cryptography", "drug_discovery", "optimization_problems"],
      "quantum_advantage": "Significant speedups in solving certain problems"
    }
  }
}
```
assistant