In a quantum harmonic oscillator problem, \(\hat{a}\) and \(\widehat{N}\) are the annihilation operator and the number operator, respectively. The operator \(e^{\hat{N}} \hat{a} e^{-\hat{N}}\) is
(where \(\hat{I}\) is the identity operator)
1
\(\hat{a}\)
2
\(e^{-1} \hat{a}\)
3
\(e^{-(\hat{i}+\hat{a})}\)
4
\(e^{\hat{a}}\)