Clean up examples and README (#357)

* removed relative import warning from examples

* Cleaner examples

README.md

@@ -5,15 +5,15 @@
 
 The Quantum Information Software Kit (**QISKit** for short) is a software development kit (SDK) for
 working with [OpenQASM](https://github.com/QISKit/qiskit-openqasm) and the
-[IBM Q experience (QX)](https://quantumexperience.ng.bluemix.net/).
+[IBM Q Experience (QX)](https://quantumexperience.ng.bluemix.net/).
 
 Use **QISKit** to create quantum computing programs, compile them, and execute them on one of
 several backends (online Real quantum processors, online simulators, and local simulators). For
 the online backends, QISKit uses our [python API client](https://github.com/QISKit/qiskit-api-py)
-to connect to the IBM Q experience.
+to connect to the IBM Q Experience.
 
 **We use GitHub issues for tracking requests and bugs. Please see the**
-[IBM Q experience community](https://quantumexperience.ng.bluemix.net/qx/community) **for
+[IBM Q Experience community](https://quantumexperience.ng.bluemix.net/qx/community) **for
 questions and discussion.**
 
 **If you'd like to contribute to QISKit, please take a look at our**
@@ -64,7 +64,7 @@ If during the installation PIP doesn't succeed to build, don't worry, you will h
 
 #### Setup your environment
 
-We recommend using python virtual environments to improve your experience. Refer to our
+We recommend using python virtual environments to improve your Experience. Refer to our
 [Environment Setup documentation](doc/install.rst#3.1-Setup-the-environment) for more information.
 
 ## Creating your first Quantum Program
@@ -76,40 +76,40 @@ We are ready to try out a quantum circuit example, which runs via the local simu
 This is a simple example that makes an entangled state.
 
 ```python
-from qiskit import QuantumProgram, QISKitError, RegisterSizeError
-
-# Create a QuantumProgram object instance.
-q_program = QuantumProgram()
-backend = 'local_qasm_simulator'
-try:
-    # Create a Quantum Register called "qr" with 2 qubits.
-    quantum_reg = q_program.create_quantum_register("qr", 2)
-    # Create a Classical Register called "cr" with 2 bits.
-    classical_reg = q_program.create_classical_register("cr", 2)
-    # Create a Quantum Circuit called "qc" involving the Quantum Register "qr"
-    # and the Classical Register "cr".
-    quantum_circuit = q_program.create_circuit("bell", [quantum_reg],[classical_reg])
-
-    # Add the H gate in the Qubit 0, putting this qubit in superposition.
-    quantum_circuit.h(quantum_reg[0])
-    # Add the CX gate on control qubit 0 and target qubit 1, putting
-    # the qubits in a Bell state
-    quantum_circuit.cx(quantum_reg[0], quantum_reg[1])
-
-    # Add a Measure gate to see the state.
-    quantum_circuit.measure(quantum_reg, classical_reg)
-
-    # Compile and execute the Quantum Program in the local_qasm_simulator.
-    result = q_program.execute(["bell"], backend=backend, shots=1024, seed=1)
-
-    # Show the results.
-    print(result)
-    print(result.get_data("bell"))
-
-except QISKitError as ex:
-    print('There was an error in the circuit!. Error = {}'.format(ex))
-except RegisterSizeError as ex:
-    print('Error in the number of registers!. Error = {}'.format(ex))
+# Import the QISKit SDK
+import qiskit
+
+# Create a Quantum Register called "qr" with 2 qubits
+qr = qiskit.QuantumRegister("qr", 2)
+# Create a Classical Register called "cr" with 2 bits
+cr = qiskit.ClassicalRegister("cr", 2)
+# Create a Quantum Circuit called involving "qr" and "cr"
+qc = qiskit.QuantumCircuit(qr, cr)
+
+# Add a H gate on the 0th qubit in "qr", putting this qubit in superposition.
+qc.h(qr[0])
+# Add a CX (CNOT) gate on control qubit 0 and target qubit 1, putting
+# the qubits in a Bell state.
+qc.cx(qr[0], qr[1])
+# Add a Measure gate to see the state.
+# (Ommiting the index applies an operation on all qubits of the register(s))
+qc.measure(qr, cr)
+
+# Create a Quantum Program for execution 
+qp = qiskit.QuantumProgram()
+# Add the circuit you created to it, and call it the "bell" circuit.
+# (You can add multiple circuits to the same program, for batch execution)
+qp.add_circuit("bell", qc)
+
+# See a list of available local simulators
+print("Local backends: ", qiskit.backends.discover_local_backends())
+
+# Compile and run the Quantum Program on a simulator backend
+sim_result = qp.execute("bell", backend='local_qasm_simulator', shots=1024, seed=1)
+
+# Show the results
+print("simulation: ", sim_result)
+print(sim_result.get_counts("bell"))
 ```
 
 In this case, the output will be:
@@ -119,21 +119,22 @@ COMPLETED
 {'counts': {'00': 512, '11': 512}}
 ```
 
-This script is available [here](examples/python/hello_quantum.py).
+This script is available [here](examples/python/hello_quantum.py), where we also show how to
+run the same program on a real quantum computer.
 
 ### Executing your code on a real Quantum chip
 
 You can also use QISKit to execute your code on a
-[real Quantum Chip](https://github.com/QISKit/ibmqx-backend-information).
-In order to do so, you need to configure the SDK for using the credentials for
+[real quantum chip](https://github.com/QISKit/ibmqx-backend-information).
+In order to do so, you need to configure the SDK for using the credentials in
 your Quantum Experience Account:
 
 
-#### Configure your API token and QE credentials
+#### Configure your API token and QX credentials
 
 
-1. Create an _[IBM Q experience](https://quantumexperience.ng.bluemix.net) > Account_ if you haven't already done so.
-2. Get an API token from the IBM Q experience website under _My Account > Personal Access Token_. This API token allows you to execute your programs with the IBM Q experience backends. See: [Example](doc/example_real_backend.rst).
+1. Create an _[IBM Q Experience](https://quantumexperience.ng.bluemix.net) > Account_ if you haven't already done so.
+2. Get an API token from the IBM Q Experience website under _My Account > Advanced > API Token_. This API token allows you to execute your programs with the IBM Q Experience backends. See: [Example](doc/example_real_backend.rst).
 3. We are going to create a new file called `Qconfig.py` and insert the API token into it. This file must have these contents:
 
   ```python
@@ -150,7 +151,7 @@ your Quantum Experience Account:
 
 4. Substitute `MY_API_TOKEN` with your real API Token extracted in step 2.
 
-5. If you have access to the IBM Q features, you also need to setup the
+5. If you have access to the IBM Q network, you also need to setup the
    values for your hub, group, and project. You can do so by filling the
    `config` variable with the values you can find on your IBM Q account
    page.
@@ -207,7 +208,7 @@ QISKit was originally developed by researchers and developers on the
 [IBM-Q](http://www.research.ibm.com/ibm-q/) Team at [IBM Research](http://www.research.ibm.com/),
 with the aim of offering a high level development kit to work with quantum computers.
 
-Visit the [IBM Q experience community](https://quantumexperience.ng.bluemix.net/qx/community) for
+Visit the [IBM Q Experience community](https://quantumexperience.ng.bluemix.net/qx/community) for
 questions and discussions on QISKit and quantum computing more broadly. If you'd like to
 contribute to QISKit, please take a look at our [contribution guidelines](CONTRIBUTING.rst).
 
@@ -219,8 +220,8 @@ contribute to QISKit, please take a look at our [contribution guidelines](CONTRI
 ## Authors (alphabetical)
 
 Ismail Yunus Akhalwaya, Luciano Bello, Jim Challenger, Andrew Cross, Vincent Dwyer, Mark Everitt, Ismael Faro,
-Jay Gambetta, Juan Gomez, Yunho Maeng, Paco Martin, Antonio Mezzacapo, Diego Moreda, Jesus Perez,
-Russell Rundle, Todd Tilma, John Smolin, Erick Winston, Chris Wood.
+Jay Gambetta, Juan Gomez, Ali Javadi-Abhari, Yunho Maeng, Paco Martin, Antonio Mezzacapo, Diego Moreda,
+Jesus Perez, Russell Rundle, Todd Tilma, John Smolin, Erick Winston, Chris Wood.
 
 In future releases, anyone who contributes with code to this project is welcome to include their
 name here.

examples/python/basic_optimize.py

@@ -16,16 +16,11 @@
 # limitations under the License.
 # =============================================================================
 
-"""Demo basic optimization: Remove Zero Rotations and Remove Double CNOTs."""
+"""Demo basic optimization: Remove Zero Rotations and Remove Double CNOTs.
 
-import os
-import sys
-
-# We don't know from where the user is running the example,
-# so we need a relative position from this file path.
-# TODO: Relative imports for intra-package imports are highly discouraged.
-# http://stackoverflow.com/a/7506006
-sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
+"""
 
 from qiskit import QuantumProgram
 from qiskit import CompositeGate

examples/python/ghz.py

@@ -17,18 +17,12 @@
 
 """
 GHZ state example illustrating mapping onto the backend.
-"""
 
-import sys
-import os
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
+"""
 
-# We don't know from where the user is running the example,
-# so we need a relative position from this file path.
-# TODO: Relative imports for intra-package imports are highly discouraged.
-# http://stackoverflow.com/a/7506006
-sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
 from qiskit import QuantumProgram
-
 import Qconfig
 
 ###############################################################

examples/python/hello_quantum.py

@@ -1,59 +1,78 @@
 """
-Example used in the readme. In this example a Bell state is made
+Example used in the README. In this example a Bell state is made.
+
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
 """
-import sys
-import os
-from pprint import pprint
-# so we need a relative position from this file path.
-# TODO: Relative imports for intra-package imports are highly discouraged.
-# http://stackoverflow.com/a/7506006
-sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
-from qiskit import QuantumProgram, QISKitError, RegisterSizeError
-
-# Create a QuantumProgram object instance.
-Q_program = QuantumProgram()
+
+# Import the QISKit SDK
+import qiskit
+# Import the IBMQ Experience API
+from IBMQuantumExperience import IBMQuantumExperience
+
+# Authenticate for access to remote backends
 try:
     import Qconfig
-    Q_program.set_api(Qconfig.APItoken, Qconfig.config["url"], verify=False,
-                      hub=Qconfig.config["hub"],
-                      group=Qconfig.config["group"],
-                      project=Qconfig.config["project"])
+    api = IBMQuantumExperience(token=Qconfig.APItoken,
+                               config={'url': Qconfig.config['url']})
+    remote_backends = qiskit.backends.discover_remote_backends(api)
 except:
-    offline = True
     print("""WARNING: There's no connection with IBMQuantumExperience servers.
-             cannot test I/O intesive tasks, will only test CPU intensive tasks
-             running the jobs in the local simulator""")
+             Have you initialized a Qconfig.py file with your personal token?
+             For now, there's only access to local simulator backends...""")
+local_backends = qiskit.backends.discover_local_backends()
 
-print("The backends available for use are:")
-pprint(Q_program.available_backends())
-print("\n")
-backend = 'local_qasm_simulator'
 try:
     # Create a Quantum Register called "qr" with 2 qubits.
-    qr = Q_program.create_quantum_register("qr", 2)
+    qr = qiskit.QuantumRegister("qr", 2)
     # Create a Classical Register called "cr" with 2 bits.
-    cr = Q_program.create_classical_register("cr", 2)
-    # Create a Quantum Circuit called "qc". involving the Quantum Register "qr"
-    # and the Classical Register "cr".
-    qc = Q_program.create_circuit("bell", [qr], [cr])
+    cr = qiskit.ClassicalRegister("cr", 2)
+    # Create a Quantum Circuit called involving "qr" and "cr"
+    qc = qiskit.QuantumCircuit(qr, cr)
 
-    # Add the H gate in the Qubit 0, putting this qubit in superposition.
+    # Add a H gate on qubit 0, putting this qubit in superposition.
     qc.h(qr[0])
-    # Add the CX gate on control qubit 0 and target qubit 1, putting 
-    # the qubits in a Bell state
+    # Add a CX (CNOT) gate on control qubit 0 and target qubit 1, putting
+    # the qubits in a Bell state.
     qc.cx(qr[0], qr[1])
-
     # Add a Measure gate to see the state.
     qc.measure(qr, cr)
 
-    # Compile and execute the Quantum Program in the local_qasm_simulator.
-    result = Q_program.execute(["bell"], backend=backend, shots=1024, seed=1)
+    # Create a Quantum Program for execution
+    qp = qiskit.QuantumProgram()
+    # Add the circuit you created to it, and call it the "bell" circuit.
+    # (You can add multiple circuits to the same program, for batch execution)
+    qp.add_circuit("bell", qc)
+
+    # Compile and run the Quantum Program on a simulator backend
+    print("(Local Backends)")
+    for backend in local_backends:
+        print(backend)
+    sim_result = qp.execute("bell", backend='local_qasm_simulator', shots=1024, seed=1)
+
+    # Show the results
+    print("simulation: ", sim_result)
+    print(sim_result.get_counts("bell"))
+
+    # Compile and run the Quantum Program on a real device backend
+    if remote_backends:
+        # see a list of available remote backends
+        print("\n(Remote Backends)")
+        for backend in remote_backends:
+            backend_status = api.backend_status(backend)
+            print(backend, backend_status)
+
+        # select least busy available device and execute
+        device_status = [api.backend_status(backend)
+                         for backend in remote_backends if "simulator" not in backend]
+        best_device = min([x for x in device_status if x['available']==True],
+                          key=lambda x:x['pending_jobs'])
+        print("Running on current least busy device: ", best_device['backend'])
+        exp_result = qp.execute("bell", backend=best_device['backend'], shots=1024, timeout=300)
 
-    # Show the results.
-    print(result)
-    print(result.get_data("bell"))
+        # Show the results
+        print("experiment: ", exp_result)
+        print(exp_result.get_counts("bell"))
 
-except QISKitError as ex:
+except qiskit.QISKitError as ex:
     print('There was an error in the circuit!. Error = {}'.format(ex))
-except RegisterSizeError as ex:
-    print('Error in the number of registers!. Error = {}'.format(ex))

examples/python/initialize.py

@@ -16,15 +16,15 @@
 # =============================================================================
 
 """
-Demo the use of the InitializeGate class to prepare arbitrary pure states.
+Example use of the initialize gate to prepare arbitrary pure states.
+
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
 """
 
 import math
-import os
-import sys
-
-from qiskit.tools.visualization import plot_circuit
 from qiskit import QuantumProgram
+from qiskit.tools.visualization import plot_circuit
 import Qconfig
 
 

examples/python/qft.py

@@ -17,17 +17,12 @@
 
 """
 Quantum Fourier Transform examples.
+
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
 """
 
-import sys
-import os
 import math
-
-# We don't know from where the user is running the example,
-# so we need a relative position from this file path.
-# TODO: Relative imports for intra-package imports are highly discouraged.
-# http://stackoverflow.com/a/7506006
-sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
 from qiskit import QuantumProgram
 
 import Qconfig

examples/python/rippleadd-async.py

@@ -16,19 +16,15 @@
 # =============================================================================
 
 """
-Ripple adder example based on Cuccaro et al, quant-ph/0410184.
+Ripple adder example based on Cuccaro et al., quant-ph/0410184.
+
+Note: if you have only cloned the QISKit repository but not
+used `pip install`, the examples only work from the root directory.
 """
 
-import sys
-import os
 import time
-
-# We don't know from where the user is running the example,
-# so we need a relative position from this file path.
-# TODO: Relative imports for intra-package imports are highly discouraged.
-# http://stackoverflow.com/a/7506006
-sys.path.append(os.path.join(os.path.dirname(__file__), '../..'))
-from qiskit import QuantumProgram, QuantumCircuit
+from qiskit import QuantumProgram
+from qiskit import QuantumCircuit
 
 import Qconfig