bug fix on ibm example; new aqt example; updated the main README file (#368)

Co-authored-by: dbretaud <logiciqt@gmail.com>

Author: dbretaud

README.rst

@@ -102,16 +102,34 @@ Instead of simulating a quantum program, one can use our resource counter (as a
 
 **Running a quantum program on IBM's QE chips**
 
-To run a program on the IBM Quantum Experience chips, all one has to do is choose the `IBMBackend` and the corresponding compiler:
+To run a program on the IBM Quantum Experience chips, all one has to do is choose the `IBMBackend` and the corresponding setup:
 
 .. code-block:: python
 
     import projectq.setups.ibm
     from projectq.backends import IBMBackend
     
+    token='MY_TOKEN'
     device='ibmq_16_melbourne'
-    compiler_engines = projectq.setups.ibm.get_engine_list(device=device)
-    eng = MainEngine(IBMBackend(use_hardware=True, num_runs=1024,
+    compiler_engines = projectq.setups.ibm.get_engine_list(token=token,device=device)
+    eng = MainEngine(IBMBackend(token=token, use_hardware=True, num_runs=1024,
+                                verbose=False, device=device),
+                     engine_list=compiler_engines)
+
+
+**Running a quantum program on AQT devices**
+
+To run a program on the AQT trapped ion quantum computer, choose the `AQTBackend` and the corresponding setup:
+
+.. code-block:: python
+
+    import projectq.setups.aqt
+    from projectq.backends import AQTBackend
+    
+    token='MY_TOKEN'
+    device='aqt_device'
+    compiler_engines = projectq.setups.aqt.get_engine_list(token=token,device=device)
+    eng = MainEngine(AQTBackend(token=token,use_hardware=True, num_runs=1024,
                                 verbose=False, device=device),
                      engine_list=compiler_engines)
 

examples/aqt.py

@@ -0,0 +1,67 @@
+import matplotlib.pyplot as plt
+import getpass
+
+from projectq import MainEngine
+from projectq.backends import AQTBackend
+from projectq.libs.hist import histogram
+from projectq.ops import Measure, Entangle, All
+import projectq.setups.aqt
+
+
+def run_entangle(eng, num_qubits=3):
+    """
+    Runs an entangling operation on the provided compiler engine.
+
+    Args:
+        eng (MainEngine): Main compiler engine to use.
+        num_qubits (int): Number of qubits to entangle.
+
+    Returns:
+        measurement (list<int>): List of measurement outcomes.
+    """
+    # allocate the quantum register to entangle
+    qureg = eng.allocate_qureg(num_qubits)
+
+    # entangle the qureg
+    Entangle | qureg
+
+    # measure; should be all-0 or all-1
+    All(Measure) | qureg
+
+    # run the circuit
+    eng.flush()
+
+    # access the probabilities via the back-end:
+    # results = eng.backend.get_probabilities(qureg)
+    # for state in results:
+    #     print("Measured {} with p = {}.".format(state, results[state]))
+    # or plot them directly:
+    histogram(eng.backend, qureg)
+    plt.show()
+
+    # return one (random) measurement outcome.
+    return [int(q) for q in qureg]
+
+
+if __name__ == "__main__":
+    #devices available to subscription:
+    # aqt_simulator (11 qubits)
+    # aqt_simulator_noise (11 qubits)
+    # aqt_device (4 qubits)
+    # 
+    # To get a subscription, create a profile at :
+    # https://gateway-portal.aqt.eu/
+    #  
+    device = None # replace by the AQT device name you want to use
+    token = None  # replace by the token given by AQT
+    if token is None:
+        token = getpass.getpass(prompt='AQT token > ')
+    if device is None:
+        device = getpass.getpass(prompt='AQT device > ')
+    # create main compiler engine for the AQT back-end
+    eng = MainEngine(AQTBackend(use_hardware=True, token=token, num_runs=200,
+                                verbose=False, device=device),
+                     engine_list=projectq.setups.aqt.get_engine_list(
+                         token=token, device=device))
+    # run the circuit and print the result
+    print(run_entangle(eng))

examples/ibm.py

@@ -48,12 +48,17 @@ def run_entangle(eng, num_qubits=3):
     # ibmq_16_melbourne (15 qubit)
     # ibmq_essex (5 qubit)
     # ibmq_qasm_simulator (32 qubits)
+    # and plenty of other 5 qubits devices!
+    #
+    # To get a token, create a profile at:
+    # https://quantum-computing.ibm.com/
+    #
     device = None # replace by the IBM device name you want to use
     token = None  # replace by the token given by IBMQ
     if token is None:
         token = getpass.getpass(prompt='IBM Q token > ')
     if device is None:
-        token = getpass.getpass(prompt='IBM device > ')
+        device = getpass.getpass(prompt='IBM device > ')
     # create main compiler engine for the IBM back-end
     eng = MainEngine(IBMBackend(use_hardware=True, token=token, num_runs=1024,
                                 verbose=False, device=device),