May 7, 2020
Introduction to Quantum Computing
using IBMQ
Applications
- Game design
- Quantum Chemistry to calculate bond lengths between atoms
Setup
pip install qiskit- Get IBM token from quantum-computing.ibm.com
Coding
from qiskit import *qr = QuantumRegister(2)
cr = ClassicalRegister(2)circuit = QuantumCircuit(qr,cr)
circuit.draw()
To build entanglements, we need gates… Hadamard gates.
circuit = circuit.h(qr[0])
circuit.draw(output='mp1')Controlled X like logical if. Say here control is qr[0] and the target is qr[1]
circuit.cx(qr[0],qr[1])Measure the qubits, take those bits and store in classical bits
circuit.measure(qr,cr) #qr=>crSimulate the circuit locally using Aer
simulator = Aer.simulate('qasm-simulator')Execute the circuit which returns results
result = execute(circuit,backend=simulator).result()Visualize
from qiskit.tools.visualization import plot_histogram
plot_histogram(result.get_counts(circuit))Place on Quantum Computer and test
from qiskit import IBMQIBMQ.save('...')IBMQ.load_account()provider = IBMQ.get_provider('ibm-q')qcomp = provider.get_backend('ibmq_16_melbourne')job = execute(circuit,backend=qcomp)
The job is placed on Qcomp but it doesn't execute immediately. Others might be using the same Qcomp, so it may take time to return. We can monitor the job by job_monitor
from qiskit.tools.monitor import job_monitorjob_monitor(job)result = job.result()
Different ways people discuss the quantum state:
- Bracket representation — state vector simulator
- Gates can be represented as matrices and operations on it are operations on vectors — unitary simulator
- Bloch sphere (visual representation of state) — state vector simulator
- How circuit works as a result of measurement — qasm simulator
[1 0] is state 0> [0 1] is state 1> [0 1, 1 0] is state of X
Gates: https://quantum-computing.ibm.com/docs/circ-comp/q-gates
Quantum Algorithms
Quantum Teleportation:
When we want to copy one qbit info to another, simple copy results in change measurement destroy the state. We take help of entanglement for quantum teleportation.
Bernstein Vazirani Algorithm:
Quantum computer can guess a secret number of n bits in one shot which takes n shots in classical computer.
