The problem of using qcircuit package in Sringer Nature journal latex template

Question

I cannot use qcircuit package in Springer Nature journal template, the latex template for Springer journal papers. It makes an error when I use that package in that template. Could anybody please help me?

Answer 1

The sn-jnl class loads the package program. From CTAN:

its main offering is a program environment; a programbox environment is available for fragments that must not break with the pages.

Unfortunately, it defines a command \push that conflicts with the qcircuit package. If you don't need such "programbox environment", you can avoid loading the package program.

Using the solution from disable loading the package program

% !TeX TS-program = pdflatex

\makeatletter% added <<<<<<<<<<<<<<<<
\disable@package@load{program}{}
\makeatother

\documentclass[pdflatex,sn-mathphys]{sn-jnl}

\usepackage{braket}
\usepackage{qcircuit}

\begin{document}

\centerline{%
        \Qcircuit @C=1em @!R {
            \lstick{\ket{x}}   &   \qw   &   \ctrl{1}   &   \qw   &   \rstick{\ket{x}}   \qw                     \\
            \lstick{\ket{y}}   &   \qw   &   \ctrl{1}   &   \qw   &   \rstick{\ket{y}}   \qw                     \\
            \lstick{\ket{z}}   &   \qw   &   \targ      &   \qw   &   \rstick{\ket{x \oplus (y \wedge z})} \qw
        }
}

\end{document}