# Magnetic Field from quantized vector potential

1. Apr 11, 2010

### vaibhavtewari

1. The problem statement, all variables and given/known data

Please help me find curl of A(vector potential) to find the magnetic field in the case of quantizes EnM fields.

2. Relevant equations

$$\vec{A}=\sum_{k,\lambda } e^{ikr}\sqrt{2\hbar / \omega_k}}\sqrt{\pi c^2/V}}(b_{\lambda,k} \hat{\epsilon}_{\lambda}(k)+b^{\dagger}_{\lambda,-k} \hat{\epsilon}_{\lambda}^{*}(-k))$$

V is the volume which is quantized. Time dependence is in the $$b, b^{\dagger}$$ itself.