Photonic Qubits

Polarization, path, time-bin, and frequency encoding

Trapping Technique

1. Photons propagate through optical fibers or integrated waveguides
2. No physical trapping required; photons travel at speed of light
3. Waveguides confine photons spatially using total internal reflection
4. Optical cavities can temporarily store photons for processing
5. Photons can be delayed using optical delay lines for synchronization
6. Quantum memories can store photon states for later retrieval

Gate Mechanism

1. Single-qubit gates use linear optical elements: beam splitters, phase shifters, wave plates
2. Beam splitters create superpositions by splitting photon paths
3. Phase shifters add relative phase between basis states
4. Polarization gates use wave plates to rotate photon polarization
5. Two-qubit gates require nonlinearity, achieved via measurement-induced nonlinearity
6. Photon detection and feed-forward create effective nonlinear interactions
7. Fusion gates combine photons probabilistically to create entanglement