(a) Define the Heisenberg picture of quantum mechanics in relation to the Schrödinger picture. Explain how the two pictures provide equivalent descriptions of physical results.

(b) Derive the equation of motion for an operator in the Heisenberg picture.

For a particle of mass $m$ moving in one dimension, the Hamiltonian is

$$\hat{H}=\frac{\hat{p}^{2}}{2 m}+V(\hat{x})$$

where $\hat{x}$ and $\hat{p}$ are the position and momentum operators, and the state vector is $|\Psi\rangle$. The eigenstates of $\hat{x}$ and $\hat{p}$ satisfy

$$\langle x \mid p\rangle=\frac{1}{\sqrt{2 \pi \hbar}} e^{i p x / \hbar}, \quad\left\langle x \mid x^{\prime}\right\rangle=\delta\left(x-x^{\prime}\right), \quad\left\langle p \mid p^{\prime}\right\rangle=\delta\left(p-p^{\prime}\right) .$$

Use standard methods in the Dirac formalism to show that

$$\begin{gathered} \left\langle x|\hat{p}| x^{\prime}\right\rangle=-i \hbar \frac{\partial}{\partial x} \delta\left(x-x^{\prime}\right) \\ \left\langle p|\hat{x}| p^{\prime}\right\rangle=i \hbar \frac{\partial}{\partial p} \delta\left(p-p^{\prime}\right) \end{gathered}$$

Calculate $\left\langle x|\hat{H}| x^{\prime}\right\rangle$ and express $\langle x|\hat{p}| \Psi\rangle,\langle x|\hat{H}| \Psi\rangle$ in terms of the position space wavefunction $\Psi(x)$.

Write down the momentum space Hamiltonian for the potential

$$V(\hat{x})=m \omega^{2} \hat{x}^{4} / 2$$