An integrated source of spectrally filtered correlated photons for large scale quantum photonic systems (1409.8215v1)

Abstract: We demonstrate the generation of quantum-correlated photon-pairs combined with the spectral filtering of the pump field by more than 95dB using Bragg reflectors and electrically tunable ring resonators. Moreover, we perform demultiplexing and routing of signal and idler photons after transferring them via a fiber to a second identical chip. Non-classical two-photon temporal correlations with a coincidence-to-accidental ratio of 50 are measured without further off-chip filtering. Our system, fabricated with high yield and reproducibility in a CMOS process, paves the way toward truly large-scale quantum photonic circuits by allowing sources and detectors of single photons to be integrated on the same chip.

Integrated Source of Correlated Photons for Quantum Photonic Systems

The paper "An Integrated Source of Spectrally Filtered Correlated Photons for Large Scale Quantum Photonic Systems" addresses a significant challenge in quantum photonics: the generation and manipulation of photon pairs within highly integrated circuits. This paper demonstrates a method to achieve high-efficiency creation and management of quantum-correlated photon pairs using silicon photonics, which is fabricated using CMOS-compatible processes — vital for scalability and practical implementations.

Key Contributions and Findings

The researchers present a monolithic silicon chip featuring an integrated source for quantum-correlated photons. Key innovations include:

1. On-chip Generation of Photon Pairs: Photon pairs are generated via spontaneous four-wave mixing (sFWM) within ring resonators — a nonlinear process where photon pairs (signal and idler) are generated from input pump photons.
2. Spectral Filtering and Demultiplexing: A fine spectral filtering of the pump field by >95 dB is achieved using Bragg reflectors combined with tunable ring resonators. This strong rejection is crucial for isolating the weak photon-pair signals from the intense pump laser.
3. Coincidence-to-accidental Ratio: The system demonstrates a CAR of 50, highlighting the non-classical temporal correlations of the photon pair signals — essential for validating the quantum nature of the device outputs.

Implications and Speculative Outlook

The successful integration of photon generation, filtering, and routing on a small-scale chip provides a promising pathway for the construction of large-scale quantum systems. This integration could support various quantum technologies such as:

• Quantum Key Distribution (QKD): The time-energy entangled photons generated can be utilized for secure communications protocols.
• Boson Sampling: The demonstrable ability to generate and manage photon pairs positions this system as a potential component in quantum computing models that require probabilistic sampling of quantum states.
• Quantum Computing and Simulation: The dense integration capability of this CMOS-compatible photonic chip could contribute to developing scalable quantum computing architectures.

Future advancements might focus on further miniaturization and improvement in coupling efficiency between integrated photonic components and fiber optics to enhance scalability. Moreover, combining this technology with on-chip quantum detectors could eliminate the last remaining need for off-chip components, pushing further towards fully integrated quantum systems.

In conclusion, the demonstrated integrated photonic system reflects significant progress toward scalable quantum technologies, providing a foundation for future exploration in the field of quantum information processing.