app.py

import streamlit as st
from qiskit import QuantumCircuit, transpile
from qiskit_aer import AerSimulator  # Correct import for AerSimulator
import io
import sys

# Title for the Streamlit app
st.title("Quantum Circuit Emulator")
st.write("Paste your Qiskit code below and press 'Run' to execute.")

# Input box for Qiskit code
qiskit_code = st.text_area("Qiskit Code", height=300, value="""
# Example Qiskit Code
from qiskit import QuantumCircuit, transpile
from qiskit_aer import AerSimulator
# Create a Quantum Circuit
qc = QuantumCircuit(2, 2)
# Apply Hadamard and CNOT gates
qc.h(0)
qc.cx(0, 1)
# Measure the qubits
qc.measure([0, 1], [0, 1])
# Use AerSimulator as the backend
simulator = AerSimulator()
# Transpile the circuit for the simulator
compiled_circuit = transpile(qc, simulator)
# Execute the circuit
result = simulator.run(compiled_circuit, shots=1024).result()
# Get the measurement results
counts = result.get_counts()
print(counts)
""")

# Run button
if st.button("Run"):
    try:
        # Redirect stdout to capture print output
        old_stdout = sys.stdout
        redirected_output = io.StringIO()
        sys.stdout = redirected_output

        # Execute the pasted Qiskit code
        exec(qiskit_code)

        # Retrieve and display output
        output = redirected_output.getvalue()
        st.success("Execution successful!")
        st.text_area("Output", output, height=200)
    except Exception as e:
        st.error(f"An error occurred: {e}")
    finally:
        # Reset stdout
        sys.stdout = old_stdout