Experimental generation of single photons via active multiplexing (1007.4798v2)

Abstract: An on-demand single-photon source is a fundamental building block in quantum science and technology. We experimentally demonstrate the proof of concept for a scheme to generate on-demand single photons via actively multiplexing several heralded photons probabilistically produced from pulsed spontaneous parametric down-conversions (SPDCs). By utilizing a four-photon-pair source, an active feed-forward technique, and an ultrafast single-photon router, we show a fourfold enhancement of the output photon rate. Simultaneously, we maintain the quality of the output single-photon states, confirmed by correlation measurements. We also experimentally verify, via Hong-Ou-Mandel interference, that the router does not affect the indistinguishability of the single photons. Furthermore, we give numerical simulations, which indicate that photons based on multiplexing of four SPDC sources can outperform the heralding based on highly advanced photon-number-resolving detectors. Our results show a route for on-demand single-photon generation and the practical realization of scalable linear optical quantum information processing.

Experimental Generation of Single Photons via Active Multiplexing

The paper "Experimental generation of single photons via active multiplexing" presents a significant advancement in quantum optics, specifically in the development of on-demand single-photon sources, which are crucial for quantum information processing. The research introduces a multiplexing approach to enhance the efficiency of generating single photons using heralded single-photon sources (HSPS) based on spontaneous parametric down-conversion (SPDC).

Overview and Methodology

The paper addresses two primary challenges in utilizing HSPS: the random nature of photon pair generation and the probability of emitting multiple photon pairs. The authors propose using a multiplexing system with several SPDC sources to mitigate these issues. This system involves four SPDC sources integrated through ultrafast photon routers, effectively redirecting and enhancing the production of single photons. The multiplexing configuration applied here is spatial, using beam splitters to distribute pump power equally among sources.

Key Findings and Results

1. Enhanced Photon Generation Rate: The paper reports a fourfold increase in the single-photon generation rate using the multiplexing method compared to a single SPDC source. This result is substantiated by detailed correlation function measurements, ensuring the high quality and indistinguishability of the photons generated.
2. Quality Assurance through Hong-Ou-Mandel Interference: The authors confirm the indistinguishability of the multiplexed single photons using Hong-Ou-Mandel (HOM) interference experiments. The visibility achieved in these experiments is critical for practical quantum information applications that rely on photon interference.
3. Numerical Simulations and Theoretical Validation: The paper includes simulations comparing the multiplexed SPDC sources with the use of photon-number-resolving detectors, demonstrating that the multiplexing approach can outperform traditional heralding methods even with advanced detectors.

Implications for Quantum Information Processing

The multiplexing scheme offers a viable route to scalable linear optical quantum information processing. By ensuring higher photon generation rates without compromising quality, this method could enhance various quantum technologies, including cryptography and computation. Furthermore, the compatibility with existing integrated optics technologies suggests potential for compact, scalable systems.

Future Developments

Looking ahead, the implementation of multiplexed single-photon sources with integrated optics could lead to breakthroughs in quantum communication and computation speed. The ongoing development of low-loss fiber coupling and fast modulators will be essential to achieving practical, near-ideal single-photon sources for quantum technology applications.

Conclusion

This research provides a promising approach to overcoming current limitations in HSPS and photon generation efficiency. The successful demonstration and analysis of the multiplexing scheme highlight its potential to influence future advancements in quantum optics and related fields, paving the way for robust, scalable quantum technologies.