\documentclass[12pt]{amsart}

\usepackage{curves}
\usepackage{epic}\setlength{\unitlength}{1pt}

\begin{document}

\begin{picture}(400,400)(0,0) % max size of picture
% followed by what the lower-left corner is
% (to put the origin at the center replace (0,0) by (-200,-200))
\thicklines % optional command
% drawline: give endpoints of a sequence of 
% connected line segments
\drawline(125,350)(125,100) % left side
\drawline(175,350)(175,300)(225,350) % v at top
\drawline(225,325)(175,275)(175,225)(225,275) % upper u
\drawline(225,250)(175,200)(175,150)(225,200) % lower u
\drawline(225,175)(175,125)(175,100) % bottom right L
\drawline(125,275)(175,275) % top line of gates
\drawline(125,200)(175,200)
\drawline(125,125)(175,125)
\drawline(125,270)(175,270) % bottom line of gates
\drawline(125,195)(175,195)
\drawline(125,120)(175,120)
% curve: smoothly connects points given
\curve(175,100, 190,50, 150,20, 110,50, 125,100)
% note: curve used because the circle-arc-drawing
% command is inflexible; mostly-circular shape
% achieved by trial and error
\put(225,335){\makebox(0,0)[l]{hole $P_2$}} % right side labels
\put(225,260){\makebox(0,0)[l]{hole $P_1$}}
\put(225,185){\makebox(0,0)[l]{hole $P_0$}}
\put(147,350){\makebox(0,0)[l]{\large$\vdots$}} % ... at top
\put(80,270){\makebox(0,0)[l]{gate $N_2$}} % left side labels
\put(80,195){\makebox(0,0)[l]{gate $N_1$}}
\put(80,120){\makebox(0,0)[l]{gate $N_0$}}
\put(150, 60){\makebox(0,0)[c]{\Large$B$}} % bulb label
\end{picture}


\end{document}