3

The program I'm currently using aims to generate a cyclic representation similar to the image provided. However, upon running the code, I encounter several errors, and the output does not match the expected image. Any assistance in resolving these issues would be greatly appreciated. Image i want look like= enter image description here

"code"

 \documentclass[border=0.1cm]{revtex4-2}
%
\usepackage[dvipsnames]{xcolor}
\usepackage{tikz}
\usepackage{circuitikz}
\usepackage{qcircuit}
\usetikzlibrary{positioning, arrows.meta}
% Create style for node rectangles
\tikzstyle{state}=[
    rectangle,
    minimum width=1.5cm,
    minimum height=1cm,
    draw=white,
    thick,
    text=black,
    font=\bfseries,
    align=center,
    fill=Orange!70,
    rounded corners=5pt % Adjust the radius as needed
]

\begin{document}
% \begin{tikzpicture}[>=Stealth, thick, text=black, font=\sffamily]
%%%%
\tikzset{meter/.append style={draw, inner sep=10, rectangle, font=\vphantom{A}, minimum width=30, minimum height=10 line width=.5, path picture={\draw[black] ([shift={(.1,.3)}]path picture bounding box.south west) to[bend left=50] ([shift={(-.1,.3)}]path picture bounding box.south east);\draw[black,-latex] ([shift={(0,.1)}]path picture bounding box.south) -- ([shift={(.3,-.1)}]path picture bounding box.north);}}}
%
%
% \begin{tikzpicture}[-stealth, thick, text=black]
\begin{tikzpicture}[>=Stealth, thick, text=black, font=\sffamily]
% State q0
\node[state, minimum width=2.cm, minimum height=0.5cm] (A) at (90:2) {\rm {Optimizer}};

% State q1
\node[state, fill=NavyBlue, minimum width=2.cm, minimum height=0.5cm, left=-1 cm] (B) at (18:2) {\rm R({$\Theta$},{$X$})};
\node[above] at (B.north) {{$\Theta$}};

% Box on the side of q1
\node[state, fill=NavyBlue, minimum width=1.cm, minimum height=0.5cm] (B_side) at (3.8,0.6) {$|0\rangle$};
\node[below=0.7 cm,left=-0.4 cm] at (B_side.east) {Quantum};
\node[below=0.9cm,left=-0.4 cm] at (B_side.east) {pre-processing};
\draw[-stealth] (B_side) -- (B);
% \node[below=0.3cm, align=center, font=\footnotesize] at (B_side.east) {Quantum\\pre-processing};
% Box on top of q1
\node[state, fill=Orange, minimum width=1.5cm, minimum height=0.8cm] (B_top) at (2.2,2.1) {Data: {x}};
\node[above] at (B_top.east) {};
\draw[-stealth] (B_top) -- (B);

% State q2
\node[state, fill=NavyBlue, minimum width=1.cm, minimum height=.5cm, left=-2.2 cm] (C) at (-32:2) { 
    ~\Qcircuit @C=.4em @R=.3em{
      \gate{R_y}&\gate{R_z} &\qw & 
     \gate{R_y}&\gate{R_z}
    \protect\gategroup{1}{1}{1}{2}{0.25em}{--}
    \protect\gategroup{1}{4}{1}{5}{0.25em}{--}
    }};
\node[above=0.4cm, right=-0.0 cm] at (C.north west) {Quantum circuit};
% State q3
\node[meter, state, fill=NavyBlue, minimum width=2.cm, minimum height=0.2cm] (D) at (-147:2) {M};
% \node[meter, state, fill=NavyBlue, minimum width=2.cm, minimum height=0.5cm] (meter) at (-138:2) {M};
\node[above=0.01cm] at (D.north west) {State measurement};

% State q4
\node[state, minimum width=2.cm, minimum height=0.5cm] (E) at (162:2) {$f(|\langle y | \phi \rangle |^2 )$};
\node[above=-0.5] at (E.north) {post-processing};
% Transition q0 to q1
\draw[-stealth] (A) to[bend left=30] node[above]{Parameter} (B);

% Transition q1 to q2
\draw[-stealth] (B) to[bend left=15] node[right]{$e_1$} (C);

% Transition q2 to q3
\draw[-stealth] (C) to[bend left=15] node[right]{$e_2$} (D);

% Transition q3 to q4
\draw[-stealth] (D) to[bend left=15] node[below=-0.4 cm, right=0.1 cm]{Quantum state$ |\phi\rangle$} (E);

% Transition q4 to q0
\draw[-stealth] (E) to[bend left=30] node[left]{Classical} (A);
\end{tikzpicture}
%
\end{document}

P.S.: See my modification here, with some minor problem left, described there.

3
  • Welcome to TeX.SE!
    – Mensch
    Apr 22 at 7:17
  • Welcome. // Sorry, but ... my goodness ... Though almost all your statements are valid, it is a lot of code noise, hard to follow, hard to refactor ... better restart from scratch with a cleaner approach.
    – MS-SPO
    Apr 22 at 8:38
  • Usually it's best to append an update to your initial question. However, your answer is quite a soultion :) So for future reference I added a P.S. with a link to your answer.
    – MS-SPO
    Apr 29 at 10:36

3 Answers 3

1

In reply to your extra question.

Analysis

My first thing to do was to draw a circle for reference, to see the quite large deviations:

        % ~~~ a circle for reference              ~~~
       \draw (0,0) circle[radius=\rd];

Soon I dropped my first idea to replace each to[bend left] by individual to[bend in=, out=] statements, where each input and output angle could be adjusted manually. But that's a lot of work to do.

So I came up with the idea of

  • putting the circle behind all other paths (i.e. draw as the first one)
  • decorating it with arrows, see ch. 50.6.1 Arrow Tip Markings in the pgfmanual

Solution, from top to bottom

Load the library \usetikzlibrary{decorations.markings}.

Define decoration markings. The pecularity here is that the circle is drawn mathematically, i.e. counter clockwise. That's why the arrows are decorated as reversed arrows. You can adjust their style like with nodes. I put them red to make them more evident. The positions result from trial&error, and may be it's not so bad to have them "in the middle", more or less.

        decoration={% will put arrows along the path (here: a counter clockwise circle)
            markings,
            mark=at position 0   with {\arrowreversed[red]{Stealth}},% (0:\rd) or east, so to say
            mark=at position .15 with {\arrowreversed[red]{Stealth}},
            mark=at position .35 with {\arrowreversed[red]{Stealth}},
            mark=at position .5  with {\arrowreversed[red]{Stealth}},% west
            mark=at position .75 with {\arrowreversed[red]{Stealth}},% south
        },

So, let's decorate the circle:

        % ~~~ a circle for reference, alter with decoration ~~~
%        \draw (0,0) circle[radius=\rd];
        \draw[postaction={decorate}] (0,0) circle[radius=\rd];

Let's remove all Connections no longer needed:

        % Connections
%        \draw[->] (OP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QP.70);
%        \draw[->] (QP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QC.65);
%        \draw[->] (QC) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QM);
    %    \draw[->] (QM) to[bend left] node[arrlbl,anchor=west,pos=.8, black] {Quantum state:\\$|\phi\rangle$} (PP);
%        \draw[->] (PP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (OP);

Preserve the now missing label. There are many ways to place it, just like with any node.

        % ~~~ moved label ~~~~~~~~~~~~~~~~~
        \node[arrlbl,anchor=north west]  at (PP.300) {Quantum state:\\$|\phi\rangle$};

Now, make your adjustments. BTW, you could overwrite the state's style for the Quantum circuit to make it a bit larger e.g. by:

 \node[state,minimum height=12mm] (QC) at ( -30:\rd) {
...

result

%%%%%%%%%%%%%%%%%
%\documentclass{article} % ok to use
\documentclass[10pt,border=3mm,tikz]{standalone} % I find this more useful for development
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
% \usetikzlibrary{quantikz}
\usepackage{qcircuit}
\usepackage[absolute,overlay]{textpos}
\usetikzlibrary{shapes}
\newcommand\rd[0]{32mm} % radius for the circle placement
\usetikzlibrary{decorations.markings}           % <<< new

\begin{document}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Define the measurement symbol style
\tikzset{
    meter/.style={
        draw,
        inner sep=10pt,
        rectangle,
        font=\vphantom{A},
        minimum width=30pt,
        minimum height=10pt,
        line width=.5pt,
        path picture={
            \draw[black] ([shift={(2pt,7pt)}]path picture bounding box.south west) to[bend left=50] ([shift={(-2pt,7pt)}]path picture bounding box.south east);
            \node[anchor=center] at (path picture bounding box.center) {$M$};
            \draw[black,-latex] ([shift={(0pt,3pt)}]path picture bounding box.south) -- ([shift={(10pt,-5pt)}]path picture bounding box.north);
        }
    }
}
%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%
\begin{tikzpicture}[
        geom/.style={
            rounded corners,
            minimum width=25mm,
            minimum height=9mm,
        },
        state/.style={fill=blue!40!teal!40,geom},
        other/.style={fill=orange!40,geom},
        txt/.style={align=center,font={\small\sffamily}},
        arrlbl/.style={blue,align=center}, % < < < replace blue by black if you prefer
        % ~~~ new ~~~~~~~~~
        decoration={% will put arrows along the path (here: a counter clockwise circle)
            markings,
            mark=at position 0   with {\arrowreversed[red]{Stealth}},% (0:\rd) or east, so to say
            mark=at position .15 with {\arrowreversed[red]{Stealth}},
            mark=at position .35 with {\arrowreversed[red]{Stealth}},
            mark=at position .5  with {\arrowreversed[red]{Stealth}},% west
            mark=at position .75 with {\arrowreversed[red]{Stealth}},% south
        },
    ]
        % ~~~ a circle for reference, later with decoration ~~~
%        \draw (0,0) circle[radius=\rd];
        \draw[postaction={decorate}] (0,0) circle[radius=\rd];
        
        % Blocks
        \node[other] (OP) at (  90:\rd) {\large Optimizer};
        \node[state] (QP) at (  20:\rd) {$R(\{\vec{\Theta}\},\{\vec{X}\})$};
        \node[state] (QC) at ( -30:\rd) {
            \resizebox{.45\linewidth}{!}{
            \hspace{-.58cm}~\Qcircuit @C=.8em @R=.5em{
                \push{\cdots} &\gate{R_y} & \gate{R_z} & \gate{R_y} & \gate{R_z}&\cdots\\
                % & & & & \\ 
                % & & & & & \\
                \protect\gategroup{1}{2}{1}{3}{0.3em}{--}
                \protect\gategroup{1}{4}{1}{5}{0.3em}{--}
            }
            }
    };
        \node[meter, state] (QM) at ( 210:\rd)  {M};
        \node[other] (PP) at ( 160:\rd) {$f(|\langle y | \phi \rangle |^2 )$ };
    % ~~~ (1) relative placement of other blocks
%   \node[state] (QX) at ([xshift=\rd]QP) {QX}; % before step (5)
    \node[rounded corners, fill=blue!40!teal!40] (QX) at ([shift=(0:2)]QP)       {$|0\rangle$};
    \node[rounded corners, fill=orange!40] (DT) at ([shift=(75:2)]QP)     {\large Data: $\{\vec{X\}}$};
        % Connections
%        \draw[->] (OP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QP.70);
%        \draw[->] (QP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QC.65);
%        \draw[->] (QC) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QM);
    %    \draw[->] (QM) to[bend left] node[arrlbl,anchor=west,pos=.8, black] {Quantum state:\\$|\phi\rangle$} (PP);
%        \draw[->] (PP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (OP);
        \draw[->] (DT) -- (QP.35);
        \draw[->] (QX) -- (QP);

        % ~~~ moved label ~~~~~~~~~~~~~~~~~
        \node[arrlbl,anchor=north west]  at (PP.300) {Quantum state:\\$|\phi\rangle$};

        % Extra labels
        \node[txt] at ([shift=(-100:-0.8)]QM) {\large Quantum state measurement};
        \node[txt] at ([shift=(90:0.7)]PP) {\large Classical post-processing};
        \node[txt] at ([shift=( -85:1.0)]QX) {\large Quantum\\pre-processing};
        \node[txt] at ([shift=(-100:1.7)]QP) {\large Quantum circuit};
        \node[txt] at ([shift=(30:-1.2)]QC) {Layer i};
        \node[txt] at ([shift=(150:-1.2)]QC) {Layer i+1};
        \node[txt,font = {\large}, red] at ([shift=(128:1.3)]QP) {Parameters:\\$\{\vec\Theta\}$};
        
    \end{tikzpicture}
    \end{document}
2
  • 1
    Thanks! This is what I was looking for. One small thing, i wanted to place "Parameter: \theta" term along the arrow or circle for better visibility. i used "\node[txt,font = {\large},rotate=-60] at ([shift=(102:1.5)]QP) {Parameters:" , this serves the purpose but not properly along the circle bit tilted. any suggestion! Apr 30 at 9:13
  • Fine :) // Check for option sloped: tikz.dev/library-circuits#pgf./tikz/info:sloped . If you put the node into the circle path, probably right before the semicolon, you can reposition it via pos=.4 or so. (Untested) // Or move the Data-blcok more to the right to create some space there for theta.
    – MS-SPO
    Apr 30 at 11:03
5

Here's a starting point for you. It's unfinished, because:

  • I can't retrieve everything from your code
  • it tries to show you the stepwise iterative refinement
  • so it stops at something that could be a new starting point for you.

result

Let's look at some details:

  • I lined out the process as comments
  • (1) places unstyled nodes on a circle, where you can change its radius at \newcommand\rd[0]{35mm}
  • (2), straight connections, now shows the initial lines with a first bend introduced; don't bend too early, focus on more relevant parts first
  • for the connections label I showed a style, anchor, and for demo a position
  • the preliminary styles (3) are fine enough for now, and would be refined more to the end of creating all this
  • change-in-one-place-only are their paradigms; see e.g. the role of style geom

UNDONE so fare are the meter (couldn't find the code) and what's inside "Quantum Circuit". These are places, where you could call tikz inside tikz, which is highly discouraged.

As an alternative I suggest creating these drawings separately using the standalone class, like done here, AND \includegraphics (i.e. those .pdfs) via package graphicx. See e.g. here (PI controller) for this approach.

Now you start into a mixing phase, where you both:

  • introduce more content
  • want or have to adjust placements, styles etc.

But it should be more doable now, I hope.

% ~~~ Procedure of stepwise iterative refinement ~~~~~~~~~
% (1)   place nodes with dummy content, to check general placement
% (2)   draw straight connections; bends can be done later
% (3)   introduce preliminary styles for the blocks
% (4)   introducing extra labels for block descriptions; 
%       add+adjust styles as minimalistic as possible+needed
% (5)   start refining nodes text contents
% (6)   let's have nicer arrow tips
% (7)   first labels at connections


\documentclass[10pt,border=3mm,tikz]{standalone}
\usetikzlibrary{arrows.meta}

\newcommand\rd[0]{35mm} % radius for the circle placement

\begin{document}
 \begin{tikzpicture}[% (3)
    geom/.style={
                    rounded corners,
                    minimum width=25mm,
                    minimum height=8mm,
                },
    state/.style={fill=blue!40!teal!40,geom},
    other/.style={fill=orange!40,geom},
    txt/.style={align=center,font={\small\sffamily}},
    >={Stealth},    % (6)
    arrlbl/.style={blue,align=center},
 ]
 
    % ~~~ (1) placing your "blocks" on circle ~~~~~~~~~~ 
    %\node (OP) at (  90:\rd) {Optimizer};  % for reference: from step (1)
    \node[other] (OP) at (  90:\rd) {Optimizer};
%   \node[state] (QP) at (  20:\rd) {PreProc};
    \node[state] (QP) at (  20:\rd) {$R(\{\vec{\Theta}\},\{\vec{X}\})$};
    \node[state] (QC) at ( -30:\rd) {Quantum Circuit};
    \node[state] (QM) at ( 210:\rd) {Quantum Meas};
%   \node[other] (PP) at ( 160:\rd) {PostProc};
    \node[other] (PP) at ( 160:\rd) {$f(|\langle y | \phi \rangle |^2 )$ };
    
    % ~~~ (1) relative placement of other blocks
%   \node[state] (QX) at ([xshift=\rd]QP) {QX}; % before step (5)
    \node[state] (QX) at ([xshift=\rd]QP)       {$|0\rangle$};
    \node[other] (DT) at ([shift=(60:4)]QP)     {Data: $\{\vec{X\}}$};
    
    % ~~~ (2) draw connections ~~~~~~~~~~
    \draw[->] (OP) -- (QP);
    \draw[->] (QP) -- (QC);
    \draw[->] (QC) -- (QM);
    \draw[->] (QM) to[bend left]
                        node[arrlbl,anchor=east,pos=.3]
                            {Quantum\\state:$|\phi\rangle$}
                        (PP);
    \draw[->] (PP) -- (OP);
    

    \draw[->] (DT) -- (QP.30);  % polar: x deg at node QP's shape
    \draw[->] (QX) -- (QP);
    
    % ~~~ (4) (first) extra labels for block desciptions ~~~~
    \node[txt] at ([shift=(130:1.5)]PP) {Classical\\post-processing};
    \node[txt] at ([shift=( 60:1.0)]QX) {Quantum\\pre-processing};
    \node[txt] at ([shift=(-40:1.5)]QP) {Pre-\\processor};
    
 \end{tikzpicture}
\end{document}

For reference, kindly see my attempt to work with your code and refactor it for more read-ability. At this point it was evident to me, it should be redone from scratch with a different approach. You might be able to beautify it even more (which also reduces problems), but ... things simply were too intermixed for that.

%\documentclass[border=0.1cm]{revtex4-2}
\documentclass[10pt,border=3mm,tikz]{standalone}
%
\usepackage[dvipsnames]{xcolor}
%\usepackage{tikz}
\usepackage{circuitikz}
\usepackage{qcircuit}
\usetikzlibrary{positioning, arrows.meta}

% Create style for node rectangles
\tikzstyle{state}=[
    rectangle,
    minimum width=1.5cm,
    minimum height=1cm,
    draw=white,
    thick,
    text=black,
    font=\bfseries,
    align=center,
    fill=Orange!70,
    rounded corners=5pt % Adjust the radius as needed
]

\begin{document}
% \begin{tikzpicture}[>=Stealth, thick, text=black, font=\sffamily]
%%%%
\tikzset{
    meter/.append style={draw, inner sep=10, rectangle, font=\vphantom{A}, 
    minimum width=30, minimum height=10 line width=.5, 
    path picture={\draw[black] ([shift={(.1,.3)}]path picture bounding box.south west) to[bend left=50] ([shift={(-.1,.3)}]path picture bounding box.south east);\draw[black,-latex] ([shift={(0,.1)}]path picture bounding box.south) -- ([shift={(.3,-.1)}]path picture bounding box.north);}}
}
%
%
% \begin{tikzpicture}[-stealth, thick, text=black]
\begin{tikzpicture}[
    >=Stealth, thick, 
    text=black, 
    font=\sffamily,
    w2h/.style={minimum width=2.cm, minimum height=0.5cm},
    wh/.style={minimum width=1.cm, minimum height=0.5cm},
    fNB/.style={fill=NavyBlue},
    lbl/.style={align=center,font=\small},
]
% ~~~ placing nodes ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    % State q0
    \node[state, w2h] (A)                   at (90:2) {\rm {Optimizer}};
    
    % State q1
    \node[state,fNB,w2h, left=-1 cm] (B)    at (18:2) {\rm R({$\Theta$},{$X$})};
%   \node[above]                            at (B.north) {{$\Theta$}};
    
    % Box on the side of q1
    \node[state,fNB,wh] (B_side)            at (3.8,0.6) {$|0\rangle$};

%   % \node[below=0.3cm, align=center, font=\footnotesize] at (B_side.east) {Quantum\\pre-processing};
    % Box on top of q1
    \node[state, fill=Orange, minimum width=1.5cm, minimum height=0.8cm] (B_top) at (2.2,2.1) {Data: {x}};
%   \node[above]                            at (B_top.east) {}; % ???
    
    % State q2
    \node[state,fNB,wh, left=-2.2 cm] (C)   at (-32:2) 
    { 
%       ~\Qcircuit @C=.4em @R=.3em{
%%        \gate{R_y}&\gate{R_z} &\qw & 
%%       \gate{R_y}&\gate{R_z}
%%      \protect\gategroup{1}{1}{1}{2}{0.25em}{--}
%%      \protect\gategroup{1}{4}{1}{5}{0.25em}{--}
%       }
        ???};
%   {xyz};
%   \node[above=0.4cm, right=-0.0 cm]       at (C.north west) {Quantum circuit};
    % State q3
    \node[meter, state,fNB, minimum width=2.cm, minimum height=0.2cm] (D) at (-147:2) {M};
    % \node[meter, state, fill=NavyBlue, minimum width=2.cm, minimum height=0.5cm] (meter) at (-138:2) {M};
%   \node[above=0.01cm]                     at (D.north west) {State measurement};
    
    % State q4
    \node[state, w2h] (E)                   at (162:2) {$f(|\langle y | \phi \rangle |^2 )$};
%   \node[above=-0.5]                       at (E.north) {post-processing};

% ~~~ extra labels ~~~~~~~~~~~~~~~~~~~~
    \node[lbl,anchor=west]      at (B_side.east) {Quantum\\pre-processing};


% ~~~ drawing connections ~~~~~~~~~~~~~~~~~~~~~~~~~
\draw[-stealth] (B_side) -- (B);
\draw[-stealth] (B_top) -- (B);

    % Transition q0 to q1
    \draw[-stealth] (A) to[bend left=30] node[red,above]{Parameter} (B);
    
    % Transition q1 to q2
    \draw[-stealth] (B) to[bend left=15] node[red,right]{$e_1$} (C);
    
    % Transition q2 to q3
    \draw[-stealth] (C) to[bend left=15] node[red,right]{$e_2$} (D);
    
    % Transition q3 to q4
    \draw[-stealth] (D) to[bend left=15] node[red,below=-0.4 cm, right=0.1 cm]{Quantum state$ |\phi\rangle$} (E);
    
    % Transition q4 to q0
    \draw[-stealth] (E) to[bend left=30] node[red,left]{Classical} (A);
\end{tikzpicture}
%
\end{document}
1
  • 1
    Thank you @MS-SPO for showing on the proper development of the presentation. I followed your instructions, and now it's nearly complete, resembling the figure shown before. However, I'm encountering difficulty with arranging the arrows effectively. I'm unable to position them in a way that enhances the overall appearance of the figure, similar to the previous one – below I am sharing the modified version of the code Apr 29 at 3:41
1

This is what I modified.

%%%%%%%%%%%%%%%%%
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}
% \usetikzlibrary{quantikz}
\usepackage{qcircuit}
\usepackage[absolute,overlay]{textpos}
\usetikzlibrary{shapes}
\newcommand\rd[0]{32mm} % radius for the circle placement

\begin{document}

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Define the measurement symbol style
\tikzset{
    meter/.style={
        draw,
        inner sep=10pt,
        rectangle,
        font=\vphantom{A},
        minimum width=30pt,
        minimum height=10pt,
        line width=.5pt,
        path picture={
            \draw[black] ([shift={(2pt,7pt)}]path picture bounding box.south west) to[bend left=50] ([shift={(-2pt,7pt)}]path picture bounding box.south east);
            \node[anchor=center] at (path picture bounding box.center) {$M$};
            \draw[black,-latex] ([shift={(0pt,3pt)}]path picture bounding box.south) -- ([shift={(10pt,-5pt)}]path picture bounding box.north);
        }
    }
}
%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%
\begin{tikzpicture}[
        geom/.style={
            rounded corners,
            minimum width=25mm,
            minimum height=9mm,
        },
        state/.style={fill=blue!40!teal!40,geom},
        other/.style={fill=orange!40,geom},
        txt/.style={align=center,font={\small\sffamily}},
        arrlbl/.style={blue,align=center},
    ]
        % Blocks
        \node[other] (OP) at (  90:\rd) {\large Optimizer};
        \node[state] (QP) at (  20:\rd) {$R(\{\vec{\Theta}\},\{\vec{X}\})$};
        \node[state] (QC) at ( -30:\rd) {
    \resizebox{.45\linewidth}{!}{
    \hspace{-.58cm}~\Qcircuit @C=.8em @R=.5em{
    \push{\cdots} &\gate{R_y} & \gate{R_z} & \gate{R_y} & \gate{R_z}&\cdots\\
    % & & & & \\ 
    % & & & & & \\
    \protect\gategroup{1}{2}{1}{3}{0.3em}{--}
    \protect\gategroup{1}{4}{1}{5}{0.3em}{--}
    }
    }
    };
        \node[meter, state] (QM) at ( 210:\rd)  {M};
        \node[other] (PP) at ( 160:\rd) {$f(|\langle y | \phi \rangle |^2 )$ };
    % ~~~ (1) relative placement of other blocks
%   \node[state] (QX) at ([xshift=\rd]QP) {QX}; % before step (5)
    \node[rounded corners, fill=blue!40!teal!40] (QX) at ([shift=(0:2)]QP)       {$|0\rangle$};
    \node[rounded corners, fill=orange!40] (DT) at ([shift=(75:2)]QP)     {\large Data: $\{\vec{X\}}$};
        % Connections
        \draw[->] (OP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QP.70);
        \draw[->] (QP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QC.65);
        \draw[->] (QC) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (QM);
        \draw[->] (QM) to[bend left] node[arrlbl,anchor=west,pos=.8, black] {Quantum state:\\$|\phi\rangle$} (PP);
        \draw[->] (PP) to[bend left] node[arrlbl,anchor=west,pos=.8]{} (OP);
        \draw[->] (DT) -- (QP.35);
        \draw[->] (QX) -- (QP);

        % Extra labels
        \node[txt] at ([shift=(-100:-0.8)]QM) {\large Quantum state measurement};
        \node[txt] at ([shift=(90:0.7)]PP) {\large Classical post-processing};
        \node[txt] at ([shift=( -85:1.0)]QX) {\large Quantum\\pre-processing};
        \node[txt] at ([shift=(-100:1.7)]QP) {\large Quantum circuit};
        \node[txt] at ([shift=(30:-1.2)]QC) {Layer i};
        \node[txt] at ([shift=(150:-1.2)]QC) {Layer i+1};
        \node[txt,font = {\large}, red] at ([shift=(128:1.3)]QP) {Parameters:\\$\{\vec\Theta\}$};
    \end{tikzpicture}
    \end{document}

enter image description here

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