Add section on circuit depth to construct circuits pg (Qiskit#2553)

Related to Qiskit/qiskit#13616. It was noted that we do not have explanatory material on the concept of circuit depth; adding it here. --------- Co-authored-by: Kaelyn Ferris <[email protected]>
arnaucasau · Jan 9, 2025 · 2550860 · 2550860
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commit 2550860
Showing 1 changed file with 11 additions and 1 deletion.
diff --git a/docs/guides/construct-circuits.ipynb b/docs/guides/construct-circuits.ipynb
@@ -187,7 +187,17 @@
     "Instructions and circuits are similar in that they both describe operations on bits and qubits, but they have different purposes:\n",
     "\n",
     "- Instructions are treated as fixed, and their methods will usually return new instructions (without mutating the original object).\n",
-    "- Circuits are designed to be built over many lines of code, and [`QuantumCircuit`](/api/qiskit/qiskit.circuit.QuantumCircuit) methods often mutate the existing object.\n",
+    "- Circuits are designed to be built over many lines of code, and [`QuantumCircuit`](/api/qiskit/qiskit.circuit.QuantumCircuit) methods often mutate the existing object."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "2e451022",
+   "metadata": {},
+   "source": [
+    "### What is circuit depth?\n",
+    "\n",
+    "The [depth()](/api/qiskit/qiskit.circuit.QuantumCircuit#qiskit.circuit.QuantumCircuit.depth) of a quantum circuit is a measure of the number of “layers” of quantum gates, executed in parallel, it takes to complete the computation defined by the circuit. Because quantum gates take time to implement, the depth of a circuit roughly corresponds to the amount of time it takes the quantum computer to execute the circuit. Thus, the depth of a circuit is one important quantity used to measure if a quantum circuit can be run on a device.\n",
     "\n",
     "The rest of this page illustrates how to manipulate quantum circuits."
    ]