Modern Computer Architecture and Organization

Modern Computer Architecture and Organization, by Jim Ledin. Published by Packt Publishing.

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Chapter 14, Exercise 4

Execute the code from Exercise 3 on an IBM quantum computer.

Answer

Repeat steps 1-5 from Exercise 3 to create the quantum circuit.

Import you IBMQ account information and list the available quantum computing providers:

from qiskit import IBMQ
IBMQ.load_account()
provider = IBMQ.get_provider(group='open')
provider.backends()

If you visit the IBM Quantum Experience home page at https://quantum-computing.ibm.com/, you will be able to see the length of the job queues for the available quantum computers. Select a system with sufficient qubits for your circuit and a short job queue. This example assumes the ibmq_essex computer is your choice.
Add your job to the queue and monitor its status with these commands. The shots parameter provides a count of the number of times the circuit will be executed to collect statistical results:
```
backend = provider.get_backend('ibmq_essex')
from qiskit.tools.monitor import job_monitor
job_exp = execute(qc, backend=backend, shots=1024)
job_monitor(job_exp)
```

After the run completes you will see the line:

Job Status: job has successfully run

After the job completes, retrieve the results with this command:
```
result_exp = job_exp.result()
```
Retrieve and display the count of the number of times each bit pattern resulted from a quantum computer run:
```
counts_exp = result_exp.get_counts(qc)
counts_exp
```

Approximately 50% of the time the output bit string for this circuit should be 000 and the other 50% of the time it should be 111. However, these systems are noisy, intermediate-scale quantum (NISQ) computers. You should see results similar (but not identical) to these:

>>> counts_exp
{'000': 459, '010': 28, '011': 35, '110': 17, '111': 428, '101': 23, '100': 22, '001': 12}
>>>

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