From 807ac6f81b8a05e543822c7df343bdc3f99dab1a Mon Sep 17 00:00:00 2001
From: Jun Doi <doichan@jp.ibm.com>
Date: Thu, 25 Apr 2024 16:00:41 +0900
Subject: [PATCH] Revert "Replace example in README to using primitives"

This reverts commit b536563851cdd51ea1db27176004b3c151ae4cd7.
---
 README.md | 104 +++++++++++++++++-------------------------------------
 1 file changed, 32 insertions(+), 72 deletions(-)

diff --git a/README.md b/README.md
index 001aa87fdd..591a56f17b 100755
--- a/README.md
+++ b/README.md
@@ -46,85 +46,45 @@ the [contributing guide](CONTRIBUTING.md#building-with-gpu-support)
 for instructions on doing this.
 
 ## Simulating your first Qiskit circuit with Aer
-Now that you have Aer installed, you can start simulating quantum circuits using primitives. Here is a basic example:
+Now that you have Aer installed, you can start simulating quantum circuits with noise. Here is a basic example:
 
 ```
 $ python
 ```
 
 ```python
-from qiskit import transpile
-from qiskit.circuit.library import RealAmplitudes
-from qiskit.quantum_info import SparsePauliOp
+import qiskit
 from qiskit_aer import AerSimulator
-
-sim = AerSimulator()
-# --------------------------
-# Simulating using estimator
-#---------------------------
-from qiskit_aer.primitives import EstimatorV2
-
-psi1 = transpile(RealAmplitudes(num_qubits=2, reps=2), sim, optimization_level=0)
-psi2 = transpile(RealAmplitudes(num_qubits=2, reps=3), sim, optimization_level=0)
-
-H1 = SparsePauliOp.from_list([("II", 1), ("IZ", 2), ("XI", 3)])
-H2 = SparsePauliOp.from_list([("IZ", 1)])
-H3 = SparsePauliOp.from_list([("ZI", 1), ("ZZ", 1)])
-
-theta1 = [0, 1, 1, 2, 3, 5]
-theta2 = [0, 1, 1, 2, 3, 5, 8, 13]
-theta3 = [1, 2, 3, 4, 5, 6]
-
-estimator = EstimatorV2()
-
-# calculate [ [<psi1(theta1)|H1|psi1(theta1)>,
-#              <psi1(theta3)|H3|psi1(theta3)>],
-#             [<psi2(theta2)|H2|psi2(theta2)>] ]
-job = estimator.run(
-    [
-        (psi1, [H1, H3], [theta1, theta3]),
-        (psi2, H2, theta2)
-    ],
-    precision=0.01
-)
-result = job.result()
-print(f"expectation values : psi1 = {result[0].data.evs}, psi2 = {result[1].data.evs}")
-
-# --------------------------
-# Simulating using sampler
-# --------------------------
-from qiskit_aer.primitives import SamplerV2
-from qiskit import QuantumCircuit
-
-# create a Bell circuit
-bell = QuantumCircuit(2)
-bell.h(0)
-bell.cx(0, 1)
-bell.measure_all()
-
-# create two parameterized circuits
-pqc = RealAmplitudes(num_qubits=2, reps=2)
-pqc.measure_all()
-pqc = transpile(pqc, sim, optimization_level=0)
-pqc2 = RealAmplitudes(num_qubits=2, reps=3)
-pqc2.measure_all()
-pqc2 = transpile(pqc2, sim, optimization_level=0)
-
-theta1 = [0, 1, 1, 2, 3, 5]
-theta2 = [0, 1, 2, 3, 4, 5, 6, 7]
-
-# initialization of the sampler
-sampler = SamplerV2()
-
-# collect 128 shots from the Bell circuit
-job = sampler.run([bell], shots=128)
-job_result = job.result()
-print(f"counts for Bell circuit : {job_result[0].data.meas.get_counts()}")
- 
-# run a sampler job on the parameterized circuits
-job2 = sampler.run([(pqc, theta1), (pqc2, theta2)])
-job_result = job2.result()
-print(f"counts for parameterized circuit : {job_result[0].data.meas.get_counts()}")
+from qiskit_ibm_runtime import QiskitRuntimeService
+
+# Generate 3-qubit GHZ state
+circ = qiskit.QuantumCircuit(3)
+circ.h(0)
+circ.cx(0, 1)
+circ.cx(1, 2)
+circ.measure_all()
+
+# Construct an ideal simulator
+aersim = AerSimulator()
+
+# Perform an ideal simulation
+result_ideal = aersim.run(circ).result()
+counts_ideal = result_ideal.get_counts(0)
+print('Counts(ideal):', counts_ideal)
+# Counts(ideal): {'000': 493, '111': 531}
+
+# Construct a simulator using a noise model
+# from a real backend.
+provider = QiskitRuntimeService()
+backend = provider.get_backend("ibm_kyoto")
+aersim_backend = AerSimulator.from_backend(backend)
+
+# Perform noisy simulation
+result_noise = aersim_backend.run(circ).result()
+counts_noise = result_noise.get_counts(0)
+
+print('Counts(noise):', counts_noise)
+# Counts(noise): {'101': 16, '110': 48, '100': 7, '001': 31, '010': 7, '000': 464, '011': 15, '111': 436}
 ```
 
 ## Contribution Guidelines