Compact and programmable large-scale optical processor in free space

Area of Science:

• Quantum Information Science
• Photonics
• Optical Computing

Background:

• Integrated photonic circuits are standard for quantum information processing.
• Free-space architectures offer advantages like broad bandwidth but face scalability challenges due to circuit depth.

Purpose of the Study:

• To introduce a programmable free-space photonic platform for high-dimensional unitary transformations.
• To overcome the scalability limitations of conventional photonic circuit depth.

Main Methods:

• Encoding information in structured light modes (circular polarization, quantized transverse momenta).
• Utilizing spatial light modulators and half-wave plates in a three-layer architecture.
• Implementing translation-invariant, high-dimensional unitary transformations.

Main Results:

• Achieved quantum walks over 30 time steps in 1D and 2D lattices using only three layers.
• Distributed a single input mode across over 7,000 outputs, significantly reducing required layers.
• Demonstrated compatibility with quantum optics protocols using heralded single photons and coincidence detection.

Conclusions:

• The developed free-space platform offers a scalable solution for high-dimensional quantum simulation.
• This approach significantly reduces the complexity and depth of photonic processors.
• Establishes free-space optical processors as viable resources for advanced quantum applications.