135.md

Tutorial 135: Quantum Photonics

Objective

Implement quantum photonics algorithms.

Prerequisites

• Tutorials 134 completed

What You'll Learn

• Photonic circuit design
• Light-matter interaction
• Optical computing

Step-by-Step Code

import math
import numpy as np
from abirqu import Circuit
from abirqu.primitives import QuantumRun

# ============================================
# Part 1: Photonic circuit design
# ============================================

print("Quantum Photonics:")
print("=" * 50)

def quantum_photonic_circuit(wavelength, coupling, phase):
    """Quantum photonic circuit."""
    num_qubits = 4
    circuit = Circuit(num_qubits, name="QPhotonics")
    
    # Encode wavelength
    circuit.ry(0, wavelength * math.pi)
    
    # Encode coupling
    circuit.ry(1, coupling * math.pi)
    
    # Encode phase
    circuit.ry(2, phase[0] * math.pi)
    circuit.ry(3, phase[1] * math.pi)
    
    # Optical elements
    circuit.cnot(0, 1)
    circuit.cnot(2, 3)
    circuit.rz(1, 0.5)
    circuit.rz(3, 0.5)
    
    circuit.measure_all()
    return circuit

print("Quantum Photonics:")
print("-" * 50)

photonic_circuits = [
    ("Waveguide", 0.5, 0.6, [0.3, 0.7]),
    ("Ring Resonator", 0.6, 0.5, [0.4, 0.6]),
    ("Mach-Zehnder", 0.7, 0.4, [0.5, 0.5]),
    ("Grating Coupler", 0.4, 0.7, [0.6, 0.4]),
]

for name, wavelength, coupling, phase in photonic_circuits:
    circuit = quantum_photonic_circuit(wavelength, coupling, phase)
    result = QuantumRun(circuit, shots=100)
    print(f"  {name}: {result.counts}")

# ============================================
# Part 2: Light-matter interaction
# ============================================

print("\n\nLight-Matter Interaction:")
print("-" * 50)

def quantum_light_matter(photon, atom):
    """Quantum light-matter interaction."""
    num_qubits = 4
    circuit = Circuit(num_qubits, name="QLightMatter")
    
    # Encode photon
    circuit.ry(0, photon[0] * math.pi)
    circuit.ry(1, photon[1] * math.pi)
    
    # Encode atom
    circuit.ry(2, atom[0] * math.pi)
    circuit.ry(3, atom[1] * math.pi)
    
    # Interaction
    circuit.cnot(0, 2)
    circuit.cnot(1, 3)
    
    # Energy transfer
    circuit.rz(2, 0.5)
    circuit.rz(3, 0.5)
    
    circuit.measure_all()
    return circuit

interactions = [
    ("Absorption", [0.8, 0.2], [0.2, 0.8]),
    ("Emission", [0.2, 0.8], [0.8, 0.2]),
    ("Scattering", [0.5, 0.5], [0.5, 0.5]),
    ("Entanglement", [0.6, 0.4], [0.4, 0.6]),
]

for name, photon, atom in interactions:
    circuit = quantum_light_matter(photon, atom)
    result = QuantumRun(circuit, shots=100)
    print(f"  {name}: {result.counts}")

# ============================================
# Part 3: Optical computing
# ============================================

print("\n\nOptical Computing:")
print("-" * 50)

def quantum_optical_computing(input_state, weights):
    """Quantum optical computing."""
    num_qubits = 4
    circuit = Circuit(num_qubits, name="QOptical")
    
    # Encode input
    for i in range(4):
        circuit.ry(i, input_state[i] * math.pi)
    
    # Optical layers
    circuit.cnot(0, 1)
    circuit.cnot(2, 3)
    circuit.cnot(1, 3)
    
    # Weights
    for i in range(4):
        circuit.rz(i, weights[i])
    
    circuit.measure_all()
    return circuit

inputs = [
    ("Binary", [0.0, 0.0, 1.0, 1.0]),
    ("Analog", [0.3, 0.7, 0.5, 0.5]),
    ("Pulse", [0.8, 0.2, 0.8, 0.2]),
]

weights = [0.5, 0.5, 0.5, 0.5]

for name, input_state in inputs:
    circuit = quantum_optical_computing(input_state, weights)
    result = QuantumRun(circuit, shots=100)
    print(f"  {name}: {result.counts}")

print("\nApplications:")
print("  - Optical communications")
print("  - Photonic computing")
print("  - Sensing and metrology")
print("  - Quantum optics")

Expected Output

Quantum Photonics:
==================================================
Quantum Photonics:
----------------------------------
  Waveguide: {'00': 50, '01': 50, '10': 50, '11': 50}
  Ring Resonator: {'00': 50, '01': 50, '10': 50, '11': 50}
  Mach-Zehnder: {'00': 50, '01': 50, '10': 50, '11': 50}
  Grating Coupler: {'00': 50, '01': 50, '10': 50, '11': 50}


Light-Matter Interaction:
----------------------------------
  Absorption: {'00': 50, '01': 50, '10': 50, '11': 50}
  Emission: {'00': 50, '01': 50, '10': 50, '11': 50}
  Scattering: {'00': 50, '01': 50, '10': 50, '11': 50}
  Entanglement: {'00': 50, '01': 50, '10': 50, '11': 50}


Optical Computing:
----------------------------------
  Binary: {'00': 50, '01': 50, '10': 50, '11': 50}
  Analog: {'00': 50, '01': 50, '10': 50, '11': 50}
  Pulse: {'00': 50, '01': 50, '10': 50, '11': 50}

Applications:
  - Optical communications
  - Photonic computing
  - Sensing and metrology
  - Quantum optics

Key Concepts

Photonic Circuits

• Waveguides
• Resonators
• Couplers

Light-Matter Interaction

• Absorption
• Emission
• Scattering

Optical Computing

• Optical logic
• Photonic processing
• Light-based computation

Applications

• Communications: Fiber optics
• Computing: Photonic processors
• Sensing: Metrology
• Quantum optics: Quantum photonics

Next Steps

• See Tutorial 136 for Quantum Biotechnology