= Solution
The <canonical quantization of a real scalar field> promotes the classical equal-time brackets to the <canonical commutation relations>, in units $\hbar=1$:
$$
\boxed{\begin{aligned}
[\phi_1(t,\mathbf x),\phi_1(t,\mathbf y)]&=0,\\
[\pi_1(t,\mathbf x),\pi_1(t,\mathbf y)]&=0,\\
[\phi_1(t,\mathbf x),\pi_1(t,\mathbf y)]&=i\delta^{(3)}(\mathbf x-\mathbf y).
\end{aligned}}
$$
The <Dirac delta distribution> expresses locality of the conjugate variables. These are identities of operator-valued distributions, interpreted after spatial smearing where necessary.
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