Scaling and networking a modular photonic quantum computer

Area of Science:

• Quantum computing
• Photonics
• Integrated photonics

Background:

• Photonics is a promising platform for quantum computing due to chip integration, fiber optics, and room-temperature operation.
• Complete integrated systems with basic functionalities for universal and fault-tolerant quantum computing require experimental demonstration.

Purpose of the Study:

• To construct and demonstrate a scale model of a photonic quantum computer.
• To showcase the feasibility of integrated systems for universal and fault-tolerant quantum computation.

Main Methods:

• Constructed a quantum computer model using 35 photonic chips, 84 squeezers, and 36 photon-number-resolving detectors.
• Networked discrete, scalable modules over fiber-optic interconnects.
• Demonstrated key building blocks for universality and fault tolerance, including heralded synthesis of non-Gaussian states and adaptive measurements.

Main Results:

• Synthesized a cluster state entangled across separate chips with 86.4 billion modes.
• Implemented the foliated distance-2 repetition code with real-time decoding.
• Demonstrated heralded synthesis of resource states, real-time multiplexing, spatiotemporal cluster-state formation, and adaptive measurements.

Conclusions:

• The constructed photonic quantum computer model demonstrates the path to cross the fault-tolerant threshold.
• This work lays the foundation for scaling photonic quantum computers to address useful applications.
• Analysis of optical loss tolerances provides insights into overcoming a major hurdle for fault tolerance.