How to predict bell state for quantum circuit in IBM qiskit

[quantumadmin]

Predicting the Bell state outcome for a quantum circuit in IBM Qiskit involves running the circuit on a simulator or a real quantum device and then analyzing the measurement results. The Bell states are a set of entangled quantum states that play a fundamental role in quantum information theory.

Here's how you can predict the Bell state outcome for a quantum circuit in IBM Qiskit:

Code: Select all

from qiskit import QuantumCircuit, Aer, execute
from qiskit.visualization import plot_histogram

# Create a quantum circuit with two qubits
qc = QuantumCircuit(2)

# Create a Bell state (|00⟩ + |11⟩) using Hadamard and CNOT gates
qc.h(0)  # Apply a Hadamard gate to qubit 0
qc.cx(0, 1)  # Apply a CNOT gate with qubit 0 as the control and qubit 1 as the target

# Measure the qubits
qc.measure_all()

# Simulate the circuit
simulator = Aer.get_backend('qasm_simulator')
job = execute(qc, simulator, shots=1024)  # You can adjust the number of shots
result = job.result()
counts = result.get_counts()

# Plot the histogram of measurement outcomes
plot_histogram(counts)

In this example, we create a quantum circuit with two qubits and apply the Hadamard gate (h) to the first qubit, followed by a controlled-X gate (cx) with the first qubit as the control and the second qubit as the target. This sequence of gates creates the Bell state (|00⟩ + |11⟩).

We then measure both qubits and simulate the circuit using the qasm_simulator backend. The shots parameter determines the number of measurements or shots taken.

Finally, we plot a histogram of the measurement outcomes using plot_histogram from the Qiskit visualization module. The histogram should show roughly equal probabilities for the states |00⟩ and |11⟩, indicating the successful creation of the Bell state.

Note that you can modify the circuit to create different Bell states (|01⟩, |10⟩, |11⟩) by applying different combinations of gates.

If you have access to a real IBM Quantum device, you can replace the simulator backend with an appropriate hardware backend from IBM Quantum Experience and submit your job for execution on the actual hardware.

Make sure you have Qiskit installed (pip install qiskit) and have an active IBM Quantum Experience account to run on real devices.