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1 files changed, 15 insertions, 1 deletions

diff --git a/content/know/concept/quantum-gate/index.pdc b/content/know/concept/quantum-gate/index.pdc
index cd09094..189145f 100644
--- a/content/know/concept/quantum-gate/index.pdc
+++ b/content/know/concept/quantum-gate/index.pdc
@@ -208,6 +208,10 @@ but not always in the basis of $\ket{0}_1$, $\ket{1}_1$, $\ket{0}_2$ and $\ket{1
 With that said, the first two-qubit gate is $\mathrm{SWAP}$,
 which simply swaps $\ket{\psi_1}$ and $\ket{\psi_2}$:
 
+<a href="swap.png">
+<img src="swap.png" style="width:22%;display:block;margin:auto;">
+</a>
+
 $$\begin{aligned}
     \boxed{
         \mathrm{SWAP} =
@@ -233,6 +237,10 @@ $$\begin{aligned}
 Next, there is the **controlled NOT gate** $\mathrm{CNOT}$,
 which "flips" (applies $X$ to) $\ket{\psi_2}$ if $\ket{\psi_1}$ is true:
 
+<a href="cnot.png">
+<img src="cnot.png" style="width:22%;display:block;margin:auto;">
+</a>
+
 $$\begin{aligned}
     \boxed{
         \mathrm{CNOT} =
@@ -252,7 +260,13 @@ $$\begin{aligned}
     &= c_{00} \ket{00} + c_{01} \ket{01} + c_{11} \ket{10} + c_{10} \ket{11}
 \end{aligned}$$
 
-More generally, each one-qubit gate $U$ can be turned into a **controlled** $U$ **gate**:
+More generally, from every one-qubit gate $U$,
+we can define a two-qubit **controlled U gate** $\mathrm{CU}$,
+which applies $U$ to $\ket{\psi_2}$ if $\ket{\psi_1}$ is true:
+
+<a href="cu.png">
+<img src="cu.png" style="width:22%;display:block;margin:auto;">
+</a>
 
 $$\begin{aligned}
     \boxed{