Document mid-circuit measurements (#4029)

closes #3983 
closes #4027 

preview:
https://qiskit.github.io/documentation/pr-4029/docs/guides/measure-qubits

---------

Co-authored-by: abbycross <[email protected]>
Co-authored-by: Kaelyn Ferris <[email protected]>

Author: 3 people

docs/guides/classical-feedforward-and-control-flow.ipynb

@@ -2,15 +2,15 @@
  "cells": [
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    "cell_type": "markdown",
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+   "id": "943cf52c-41c8-4a2b-bf1d-6df8a90a6353",
    "metadata": {},
    "source": [
     "# Classical feedforward and control flow"
    ]
   },
   {
    "cell_type": "markdown",
-   "id": "e64d4278-879b-4319-9fbe-85a64327bcac",
+   "id": "b1d96290-2e64-43aa-bae9-c74b8529894d",
    "metadata": {
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      "version-info"
@@ -31,14 +31,14 @@
   },
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    "cell_type": "markdown",
-   "id": "67b2704d-aa3d-4e39-b417-536093be274e",
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    "source": [
     "<Admonition type=\"note\" title=\"Dynamic circuits now available on all backends\">\n",
     "The new version of dynamic circuits is now available to all users on all backends. You can now run dynamic circuits at utility scale. See [the announcement](/announcements/product-updates/2025-09-25-new-dynamic-circuits) for more details.\n",
     "</Admonition>\n",
     "\n",
-    "Dynamic circuits are powerful tools with which your can measure qubits in the middle of a quantum circuit execution and then perform classical logic operations within the circuit, based on the outcome of those mid-circuit measurements.  This process is also known as _classical feedforward_. While these are early days of understanding how best to take advantage of dynamic circuits, the quantum research community has already identified a number of use cases, such as the following:\n",
+    "Dynamic circuits are powerful tools with which you can measure qubits in the middle of a quantum circuit execution and then perform classical logic operations within the circuit, based on the outcome of those mid-circuit measurements.  This process is also known as _classical feedforward_. While these are early days of understanding how best to take advantage of dynamic circuits, the quantum research community has already identified a number of use cases, such as the following:\n",
     "\n",
     "* Efficient quantum state preparation, such as [GHZ state,](https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.5.030339) [W-state,](https://arxiv.org/abs/2403.07604) (for more information about W-state, also refer to [\"State preparation by shallow circuits using feed forward\"](https://arxiv.org/abs/2307.14840)) and a broad class of [matrix product states](https://arxiv.org/abs/2404.16083)\n",
     "* [Efficient long-range entanglement](https://journals.aps.org/prxquantum/abstract/10.1103/PRXQuantum.5.030339) between qubits on the same chip by using shallow circuits\n",
@@ -51,7 +51,7 @@
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-   "id": "0767b203-ad69-428f-b8c1-50ceab758b35",
+   "id": "5d846edf-fc09-4808-bd62-3a8cfdcc1585",
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    "source": [
     "## `if` statement\n",
@@ -64,13 +64,13 @@
   {
    "cell_type": "code",
    "execution_count": 1,
-   "id": "008f85d9-5b48-4e84-b250-846b07901607",
+   "id": "60924bfa-50ed-4d9d-a17b-9d64f2cc053f",
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     {
      "data": {
       "text/plain": [
-       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/008f85d9-5b48-4e84-b250-846b07901607-0.svg\" alt=\"Output of the previous code cell\" />"
+       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/60924bfa-50ed-4d9d-a17b-9d64f2cc053f-0.avif\" alt=\"Output of the previous code cell\" />"
       ]
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      "execution_count": 1,
@@ -99,7 +99,7 @@
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-   "id": "fdc99e4d-fcd0-4397-b6da-2e36a51f90a8",
+   "id": "bef3f447-7282-4de9-9410-6b671e9902c3",
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    "source": [
     "The `with` statement can be given an assignment target which is itself a context manager that can be stored and subsequently used to create an else block, which is executed whenever the contents of the `if` block are *not* executed.\n",
@@ -110,13 +110,13 @@
   {
    "cell_type": "code",
    "execution_count": 2,
-   "id": "5b22ae93-27d1-4a0c-89e2-9f88383039d6",
+   "id": "20f0640a-a3f7-41b3-aada-b66bc89b0555",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/5b22ae93-27d1-4a0c-89e2-9f88383039d6-0.svg\" alt=\"Output of the previous code cell\" />"
+       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/20f0640a-a3f7-41b3-aada-b66bc89b0555-0.avif\" alt=\"Output of the previous code cell\" />"
       ]
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      "execution_count": 2,
@@ -146,7 +146,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "d70a3dec-33fe-4a2f-942e-592770c4868e",
+   "id": "f0f00f48-a1f2-40cc-b5f5-9a122d8dd24e",
    "metadata": {},
    "source": [
     "In addition to conditioning on a single classical bit, it's also possible to condition on the value of a classical register composed of multiple bits.\n",
@@ -157,13 +157,13 @@
   {
    "cell_type": "code",
    "execution_count": 3,
-   "id": "15ac9465-c61f-4de1-81e8-e4edfafb07b4",
+   "id": "98e8f552-4169-42a3-8182-e14e9ffb59e2",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/15ac9465-c61f-4de1-81e8-e4edfafb07b4-0.svg\" alt=\"Output of the previous code cell\" />"
+       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/98e8f552-4169-42a3-8182-e14e9ffb59e2-0.avif\" alt=\"Output of the previous code cell\" />"
       ]
      },
      "execution_count": 3,
@@ -192,7 +192,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "86219c0c-4b81-405d-8cb9-3fbe00353832",
+   "id": "ef8fd422-6bab-46c9-9455-c79244cf1fb7",
    "metadata": {},
    "source": [
     "## Classical expressions\n",
@@ -208,7 +208,7 @@
   {
    "cell_type": "code",
    "execution_count": 4,
-   "id": "42454b75-8e80-4e22-9d3b-ec85746e0550",
+   "id": "7581ac2f-53e9-43d0-bad0-2c80790172e1",
    "metadata": {},
    "outputs": [],
    "source": [
@@ -267,13 +267,13 @@
   {
    "cell_type": "code",
    "execution_count": 5,
-   "id": "3bdb923d-c466-4743-99b1-d46fda9660ef",
+   "id": "d0f0abdb-50d5-408d-a704-a1a555acdd85",
    "metadata": {},
    "outputs": [
     {
      "data": {
       "text/plain": [
-       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/3bdb923d-c466-4743-99b1-d46fda9660ef-0.svg\" alt=\"Output of the previous code cell\" />"
+       "<Image src=\"/docs/images/guides/classical-feedforward-and-control-flow/extracted-outputs/d0f0abdb-50d5-408d-a704-a1a555acdd85-0.avif\" alt=\"Output of the previous code cell\" />"
       ]
      },
      "execution_count": 5,
@@ -287,7 +287,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "f01b52c8-77d3-4052-bece-75ca998e7bb5",
+   "id": "0152155a-2c6d-4f87-bf29-c306e9f1082c",
    "metadata": {},
    "source": [
     "## Find backends that support dynamic circuits\n",
@@ -301,10 +301,30 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
-   "id": "6b04b732-8143-4d76-bc43-a12ed0790bf6",
+   "execution_count": 6,
+   "id": "555e5491-de0e-49fe-b919-9ab51bed00ef",
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stderr",
+     "output_type": "stream",
+     "text": [
+      "management.get:WARNING:2025-10-28 10:10:23,538: Loading default saved account\n",
+      "qiskit_runtime_service.__init__:WARNING:2025-10-28 10:10:32,937: Instance was not set at service instantiation. Free and trial plan instances will be prioritized. Based on the following filters: (tags: None, region: us-east, eu-de), and available plans: (internal, premium), the available account instances are: Documentation premium fleet, Documentation internal fleet, Documentation premium fleet, Documentation internal fleet. If you need a specific instance set it explicitly either by using a saved account with a saved default instance or passing it in directly to QiskitRuntimeService().\n",
+      "qiskit_runtime_service.backends:WARNING:2025-10-28 10:10:32,939: Loading instance: Documentation premium fleet, plan: premium\n",
+      "qiskit_runtime_service.backends:WARNING:2025-10-28 10:10:34,963: Loading instance: Documentation internal fleet, plan: internal\n",
+      "qiskit_runtime_service.backends:WARNING:2025-10-28 10:10:35,402: Loading instance: Documentation premium fleet, plan: premium\n",
+      "qiskit_runtime_service.backends:WARNING:2025-10-28 10:10:37,875: Loading instance: Documentation internal fleet, plan: internal\n"
+     ]
+    },
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "[<IBMBackend('ibm_brussels')>, <IBMBackend('ibm_aachen')>, <IBMBackend('ibm_strasbourg')>, <IBMBackend('test_eagle_eu-de')>, <IBMBackend('ibm_fez')>, <IBMBackend('ibm_brisbane')>, <IBMBackend('ibm_pittsburgh')>, <IBMBackend('ibm_marrakesh')>, <IBMBackend('ibm_kingston')>, <IBMBackend('ibm_torino')>, <IBMBackend('ibmq_dublin')>, <IBMBackend('test_eagle_us-east')>, <IBMBackend('ibm_pinguino2')>, <IBMBackend('test_heron_pok_1')>, <IBMBackend('ibm_pinguino3')>, <IBMBackend('ibm_pinguino1')>]\n"
+     ]
+    }
+   ],
    "source": [
     "from qiskit_ibm_runtime import QiskitRuntimeService\n",
     "\n",
@@ -315,7 +335,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "0378a45f-7a28-48bc-993d-0e4308d38bfc",
+   "id": "6aca448f-2bc7-46ef-9832-01a14456d774",
    "metadata": {},
    "source": [
     "## Qiskit Runtime limitations\n",
@@ -397,7 +417,7 @@
   },
   {
    "cell_type": "markdown",
-   "id": "6aa76130-acc1-4479-8a54-edab6a133e7c",
+   "id": "7c80c5d0-a447-4590-8426-6eb33ae2d817",
    "metadata": {},
    "source": [
     "## Next steps\n",
@@ -431,5 +451,5 @@
   "title": "Classical feedforward and control flow (dynamic circuits)"
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }