Tailoring quantum walks in integrated photonic lattices

Area of Science:

• Quantum optics
• Photonic integrated circuits
• Condensed matter physics

Background:

• Discrete photonic circuits manipulate photons sequentially.
• Coupled waveguide arrays allow continuous photon interference.
• Nonlinear materials in waveguide arrays can generate quantum light states.

Purpose of the Study:

• Systematically compare linear and nonlinear waveguide arrays for quantum walks.
• Clarify similarities and distinctions between external photon injection and in-situ photon generation.
• Investigate the emergence of non-classicality in photonic quantum walks.

Main Methods:

• Experimental validation using III-V semiconductor nonlinear waveguide lattices.
• Tuning quantum walk depth via varied lattice geometries.
• Utilizing parametric down-conversion for continuous photon pair generation.
• Applying inverse-design to engineer aperiodic waveguide arrays.

Main Results:

• Demonstrated experimental validation of quantum walk predictions in nonlinear waveguide arrays.
• Revealed the gradual emergence of non-classicality with increasing quantum walk depth.
• Engineered aperiodic waveguide arrays to generate maximally entangled states, like the biphoton W-state.

Conclusions:

• Continuously-coupled photonic systems offer a promising platform for generating high-dimensional entanglement.
• Nonlinear waveguide arrays enable direct generation of quantum states within compact architectures.
• Inverse-design approaches can optimize waveguide structures for specific quantum states.