Photonic quantum information processing: a review (1803.02790v2)

Abstract: Photonic quantum technologies represent a promising platform for several applications, ranging from long-distance communications to the simulation of complex phenomena. Indeed, the advantages offered by single photons do make them the candidate of choice for carrying quantum information in a broad variety of areas with a versatile approach. Furthermore, recent technological advances are now enabling first concrete applications of photonic quantum information processing. The goal of this manuscript is to provide the reader with a comprehensive review of the state of the art in this active field, with a due balance between theoretical, experimental and technological results. When more convenient, we will present significant achievements in tables or in schematic figures, in order to convey a global perspective of the several horizons that fall under the name of photonic quantum information.

• The paper provides an in-depth analysis of photonic quantum information processing, showcasing experimental methods like single-photon generation and integrated quantum circuits.
• It reviews advanced quantum communication protocols including dense coding, quantum teleportation, and quantum key distribution enhanced by innovative detection technologies.
• The study explores quantum simulation and computing applications, demonstrating how photonic systems enable scalable, secure networks and accurate modeling of complex quantum phenomena.

Overview of Photonic Quantum Information Processing

The topic of photonic quantum information processing represents a vital area in both theoretical and experimental quantum computing and quantum communication. The utility of photons in quantum technologies arises from their rapid propagation, minimal interaction with the environment, and ease of manipulation, making them ideal carriers of quantum information. This review paper provides an in-depth analysis of the implementation methodologies, experimental advancements, and potential applications of photonics in the quantum domain.

Photonics offers a promising platform for quantum technologies, ranging from the fundamental delivery of quantum information over long distances to simulating complex quantum phenomena. This review presents a structured overview, discussing the theoretical underpinnings, experimental achievements, and technological infrastructure supporting photonic quantum information processing.

Core Technological Components

1. Single-Photon Sources: A significant aspect is the generation of single photons via processes such as spontaneous parametric down-conversion (PDC) and four-wave mixing (FWM) in various platforms, including semiconductors and optical fibers. The review details the technological strides in producing on-demand, high-brightness, and indistinguishable single photons essential for quantum information applications.
2. Integrated Quantum Circuits: It highlights the miniaturization and integration of quantum circuits using various materials, such as silicon-on-insulator (SoI) and other dielectrics. Advances in integrated photonic platforms are crucial for scaling quantum information systems and offer stability and scalability benefits over traditional bulk optics setups.
3. Detection Technologies: The paper reviews developments in photon detection technologies, including non-photon-number-resolving detectors like single-photon avalanche diodes (SPAD) and photon-number-resolving detectors such as transition-edge sensors. Integration of these detectors into photonic circuits enhances their applicability in complex quantum networks.

Quantum Communication Protocols

Photonic systems serve as the backbone for long-distance quantum communication, leveraging entanglement and superposition to achieve secure information transfer. The paper emphasizes several key protocols:

• Dense Coding and Quantum Teleportation: These fundamental concepts allow the encoding and transmission of quantum information beyond classical capabilities. The paper discusses the experimental realization of these protocols using photonic systems, emphasizing their role in future quantum networks.
• Quantum Repeaters and Decoherence-Free Subspaces: Addressing the challenges of maintaining coherence over long distances, the review introduces quantum repeaters and the concept of decoherence-free subspaces to mitigate losses in transmission systems.
• Quantum Key Distribution (QKD): With quantum attacks posing a threat to classical cryptography, photonic QKD presents a solution for secure communications. The discussion encompasses recent experimental implementations and the integration of QKD with existing telecom infrastructure using wavelength division multiplexing.

Quantum Simulation

The capabilities of photonics extend to quantum simulation, where they are employed to model quantum systems of varying complexity. The review covers:

• Quantum Walks: Both discrete and continuous-time quantum walks are used to simulate quantum transport phenomena and quantum statistical behavior in controlled photonic environments.
• BosonSampling: This specific problem provides evidence of quantum computational advantage, using linear optical setups to perform tasks believed to be classically unconquerable. The review outlines experimental achievements and challenges in scaling BosonSampling implementations.

Applications and Theoretical Implications

The potential of photonic quantum processors to simulate molecular structures and vibrational spectra underpins their significance in quantum chemistry. Furthermore, the manipulation of high-dimensional entangled states, enabled by advanced photonic technologies, offers prospects for developing sophisticated quantum networks and computing paradigms.

The paper concludes by suggesting that advancements in photonic technologies are poised to play an instrumental role in achieving practical quantum computing and communication systems. Continued technological innovation and integration within existing infrastructures will further unlock the capabilities of photonics, driving progress in the broader field of quantum sciences.

This comprehensive review thus serves as an essential resource for researchers focusing on advancing quantum information processing using photonics.