Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Advances in Photonics of Quantum Computing, Memory, and Communication

Hyper-entanglement signals in quantum optical circuits

Vladimir V. Nikulin, Rushui Fang, David H. Hughes

Published Mar 4, 2019• 1 citation
Publisher

Abstract

Secure free-space data links can be established using conventional laser communication technology or, if necessary, they can be further enhanced with quantum encryption. Security features of these systems are based on the protocols that make use of the inherent properties of laser light. In this case, encryption does not rely on complex mathematical algorithms that add overhead to the communication stream, but instead it is based on physical-layer processes in the laser sources and other modulating components. One promising approach is based on polarization entanglement between correlated photon pairs to achieve data encryption in quantum communication systems. The foundation of security lies in the response of photons to polarization measurements. Additional degrees of freedom can be added to each “singleparticle” state by using hyper-entanglement. The situation can be visualized when several carrier waves are assigned specific frequencies in the 100 GHz International Telecommunication Union (ITU) grid. The two technologies that can be eventually integrated to achieve this task include hyperspectral quantum circuits and the entangled pair source and detection systems. This results in frequency/polarization hyper-entanglement, which can be processed with additional wavelength-division multiplexing (WDM) components to achieve efficient separation of the signals. It is important to understand that most of the previous work is theoretical and assumes ideal properties of all optical parts. In reality, many non-ideal features of the quantum circuits and their components can change the way the quantum states are processed, and this constitutes the main focus of our paper.

DOI
10.1117/12.2506099

Related papers

Hyper-entanglement optical circuits for quantum communications

Vladimir V. Nikulin, Rushui Fang, John E. Malowicki +1 more

This paper discusses high-performance quantum optical circuits for processing polarization entanglement between correlated photon pairs. The primary application of this technology is secure communication links with quantum encryption that rely on the inherent properties of laser light and physical-layer processes in optical components. It can be used for generating identical pairs of encryption keys in quantum key distribution applications, for a variety of encryption protocols ranging from single-photon to multiple-photon, keyed communication in quantum noise, but we see a potential spectrum extending further to include multi-access systems. Success in these applications can be achieved by introducing additional degrees-of-freedom in each single-particle quantum state. We see hyper-entanglement as a very promising approach to do this. The concept is visualized by having multiple entangled photons with specifically assigned frequencies in the 100 GHz ITU grid and arriving simultaneously from multiple sources. Processing of such signals requires hyperspectral optical circuits capable of responding to non-classical features of quantum states. The function of these circuits is to direct the arriving signals along different processing paths to single photon detectors, which can be realized by a combination of different technologies, such as highly selective Lyot filters, dense wavelength division multiplexing, and others. Processing capabilities of these quantum circuits, while seemingly straight-forward in theory, still present a great implementation challenge. Practical operating conditions and characteristics of optical components must be taken into consideration to address the underlying design problems and make this technology feasible. This constitutes the main focus of our paper.

Quantum Communications and Quantum Imaging•Sep 6, 2019•4 citations

Hyper-entanglement preservation in quantum optical circuits

Vladimir V. Nikulin

Secure optical data links can be implemented using quantum communication (QC) protocols that offer physical-layer encryption without the mathematical complexity of traditional cryptography. Data encoding can be achieved using polarization entanglement and it is further proposed to obtain additional degrees of freedom for each single particle quantum state by using hyper-entanglement. For example, multiple carrier signals arriving at the same time can be assigned specific frequencies in the 100 GHz International Telecommunication Union (ITU) grid and be processed simultaneously by a receiver that uses a hyperspectral quantum optical circuit. In this paper, we address preservation of hyper-entanglement as the signals propagate through optical components of the quantum circuits and encounter their realistic properties.

Optical Manipulation and Structured Materials Conference (OMC)•Apr 24, 2018•1 citation

Analysis of entanglement in multi-access quantum optical circuits

Vladimir V. Nikulin

Free-space optical communication channels offer unsurpassed advantages over traditional radio frequency systems. They can be implemented in a point-to-point topology and, if necessary, augmented with additional security features for privacy-critical applications. The adoption of quantum mechanical principles in optical communication networks became a foundation for quantum communication protocols that offer added security without the mathematical complexity of traditional cryptography. Encryption can be achieved at the physical layer by using quantized values of photons, which makes exploitation of such communication links extremely difficult. Additional challenges are encountered when the focus is shifted from point-to-point links to multi-access communication systems arranged in a hub-and-spokes topology. To facilitate connectivity, the “hub” can use a single aperture to establish connection to a target platform within its fieldof- view. Polarization entanglement is proposed for data encoding, and additional degrees of freedom can be achieved for each quantum state by using hyper-entanglement. For example, if carrier waves arriving at the same time from multiple transmitters (spokes) are assigned specific frequencies in the 200 GHz ITU grid, their messages can be processed simultaneously by a receiver (hub) that uses a hyperspectral quantum optical circuit. In this paper, we present analysis of the components in the optical trains and propagation of hyper-entangled states in the quantum circuits. The results obtained in this project can be used as the first step before physical implementation of the quantum communication systems.

Quantum Computing, Communication, and Simulation•Feb 22, 2018•5 citations

Application of quantum state tomography to experimental analysis of entanglement in quantum optical circuits

Vladimir V. Nikulin, Rushui Fang, John E. Malowicki +1 more

This paper describes high-performance optical circuits operating on hyper-entangled quantum states. The concept is based on correlated photon pairs generated in such a way that their polarization, frequency or propagation paths are entangled and can be used to support quantum encryption protocols. Detection and processing of such signals requires hyper-spectral optical circuits capable of responding to non-classical features of light. Processing capabilities of these quantum circuits are straight-forward in theory, but physical implementation can still present a challenge for integrity of the quantum states. In this paper, we address experimental verification of entanglement characteristics at each step of building the quantum optical circuits and present a formal quantitative approach based on the quantum state tomography.

•Aug 26, 2020•3 citations

Quantum operations on entangled photons using Lyot filters

David H. Hughes, Reinhard K. Erdmann, Vladimir V. Nikulin

Lyot filters have been designed for multi-access high capacity wavelength division multiplexing between a communications hub and spatially separated spokes. Reported here are modifications to a basic classical communications Lyot filter stage [1], but using a hyper-entangled bipartite input state possessing non-degenerate frequencies for advanced quantum communications. Lyot filters and pre-shared linking knowledge can be used to better ensure efficiency and efficacy in manifesting entanglement correlations between polarization degrees of freedom in non-rotationally invariant measurement bases. Lyot filters also allow entangled photon routing, a function of entanglement between incident frequencies and polarization.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Oct 24, 2016•13 citations

Photonic entanglement: unleashing colour

Meritxell Cabrejo‐Ponce

Quantum information is transforming modern society with concepts like entanglement, crucial for communication, computing and sensing. To mainstream these technologies, improved efficiency in encoding, transmission and information processing is required, especially in quantum key distribution (QKD). This method aims to securely distribute encryption keys while improving key rates and overcoming propagation loss and noise. Photons serve as ideal carriers due to their various properties for encoding information and minimal environmental interaction, making them vital for the global internet. High-dimensional and hyper-entanglement offer advantages over traditional two-mode encoding methods, including increase noise tolerance and information capacity. However, practical implementation is often limited by measurement device complexities and errors. Frequencies, or photon colours, present a promising approach to boost quantum communication thanks to their compatibility with existing telecommunications infrastructure and naturally occurs in photon pair generation. This thesis explores the frequency degree of freedom for applications in QKD, utilizing efficient all-fiber photon-pair sources to generate hyper-entangled states in polarization and frequency. The incorporation of fast modulators allows for high-speed operation while maintaining high entanglement fidelity. Reconfigurable spectral filters enable tailored spectro-temporal properties to fulfil requirements in multi-user networks and protocols beyond QKD, such as quantum secret sharing. To maximize quantum information capacity, methods for efficiently characterizing frequency entanglement are developed, achieving a certification of 35 modes, a record for the time and frequency degrees of freedom. Finally, estimates of secure key rates and a discussion of noise effects is shown. This foundation supports broadband and flexible quantum networks that effectively utilize frequency encoding in the future quantum internet.

•Jan 1, 2025•0 citations
Secure free-space data links can be established using conventional laser communication technology or, if necessary, they can be further enhanced with quantum encryption. Security features of these systems are based on the protocols that make use of the inherent properties of laser light. In this case, encryption does not rely on complex mathematical algorithms that add overhead to the communication stream, but instead it is based on physical-layer processes in the laser sources and other modulating components. One promising approach is based on polarization entanglement between correlated photon pairs to achieve data encryption in quantum communication systems. The foundation of security lies in the response of photons to polarization measurements. Additional degrees of freedom can be added to each “singleparticle” state by using hyper-entanglement. The situation can be visualized when several carrier waves are assigned specific frequencies in the 100 GHz International Telecommunication Union (ITU) grid. The two technologies that can be eventually integrated to achieve this task include hyperspectral quantum circuits and the entangled pair source and detection systems. This results in frequency/polarization hyper-entanglement, which can be processed with additional wavelength-division multiplexing (WDM) components to achieve efficient separation of the signals. It is important to understand that most of the previous work is theoretical and assumes ideal properties of all optical parts. In reality, many non-ideal features of the quantum circuits and their components can change the way the quantum states are processed, and this constitutes the main focus of our paper.
This paper discusses high-performance quantum optical circuits for processing polarization entanglement between correlated photon pairs. The primary application of this technology is secure communication links with quantum encryption that rely on the inherent properties of laser light and physical-layer processes in optical components. It can be used for generating identical pairs of encryption keys in quantum key distribution applications, for a variety of encryption protocols ranging from single-photon to multiple-photon, keyed communication in quantum noise, but we see a potential spectrum extending further to include multi-access systems. Success in these applications can be achieved by introducing additional degrees-of-freedom in each single-particle quantum state. We see hyper-entanglement as a very promising approach to do this. The concept is visualized by having multiple entangled photons with specifically assigned frequencies in the 100 GHz ITU grid and arriving simultaneously from multiple sources. Processing of such signals requires hyperspectral optical circuits capable of responding to non-classical features of quantum states. The function of these circuits is to direct the arriving signals along different processing paths to single photon detectors, which can be realized by a combination of different technologies, such as highly selective Lyot filters, dense wavelength division multiplexing, and others. Processing capabilities of these quantum circuits, while seemingly straight-forward in theory, still present a great implementation challenge. Practical operating conditions and characteristics of optical components must be taken into consideration to address the underlying design problems and make this technology feasible. This constitutes the main focus of our paper.
Secure optical data links can be implemented using quantum communication (QC) protocols that offer physical-layer encryption without the mathematical complexity of traditional cryptography. Data encoding can be achieved using polarization entanglement and it is further proposed to obtain additional degrees of freedom for each single particle quantum state by using hyper-entanglement. For example, multiple carrier signals arriving at the same time can be assigned specific frequencies in the 100 GHz International Telecommunication Union (ITU) grid and be processed simultaneously by a receiver that uses a hyperspectral quantum optical circuit. In this paper, we address preservation of hyper-entanglement as the signals propagate through optical components of the quantum circuits and encounter their realistic properties.
Free-space optical communication channels offer unsurpassed advantages over traditional radio frequency systems. They can be implemented in a point-to-point topology and, if necessary, augmented with additional security features for privacy-critical applications. The adoption of quantum mechanical principles in optical communication networks became a foundation for quantum communication protocols that offer added security without the mathematical complexity of traditional cryptography. Encryption can be achieved at the physical layer by using quantized values of photons, which makes exploitation of such communication links extremely difficult. Additional challenges are encountered when the focus is shifted from point-to-point links to multi-access communication systems arranged in a hub-and-spokes topology. To facilitate connectivity, the “hub” can use a single aperture to establish connection to a target platform within its fieldof- view. Polarization entanglement is proposed for data encoding, and additional degrees of freedom can be achieved for each quantum state by using hyper-entanglement. For example, if carrier waves arriving at the same time from multiple transmitters (spokes) are assigned specific frequencies in the 200 GHz ITU grid, their messages can be processed simultaneously by a receiver (hub) that uses a hyperspectral quantum optical circuit. In this paper, we present analysis of the components in the optical trains and propagation of hyper-entangled states in the quantum circuits. The results obtained in this project can be used as the first step before physical implementation of the quantum communication systems.
This paper describes high-performance optical circuits operating on hyper-entangled quantum states. The concept is based on correlated photon pairs generated in such a way that their polarization, frequency or propagation paths are entangled and can be used to support quantum encryption protocols. Detection and processing of such signals requires hyper-spectral optical circuits capable of responding to non-classical features of light. Processing capabilities of these quantum circuits are straight-forward in theory, but physical implementation can still present a challenge for integrity of the quantum states. In this paper, we address experimental verification of entanglement characteristics at each step of building the quantum optical circuits and present a formal quantitative approach based on the quantum state tomography.
Lyot filters have been designed for multi-access high capacity wavelength division multiplexing between a communications hub and spatially separated spokes. Reported here are modifications to a basic classical communications Lyot filter stage [1], but using a hyper-entangled bipartite input state possessing non-degenerate frequencies for advanced quantum communications. Lyot filters and pre-shared linking knowledge can be used to better ensure efficiency and efficacy in manifesting entanglement correlations between polarization degrees of freedom in non-rotationally invariant measurement bases. Lyot filters also allow entangled photon routing, a function of entanglement between incident frequencies and polarization.
Quantum information is transforming modern society with concepts like entanglement, crucial for communication, computing and sensing. To mainstream these technologies, improved efficiency in encoding, transmission and information processing is required, especially in quantum key distribution (QKD). This method aims to securely distribute encryption keys while improving key rates and overcoming propagation loss and noise. Photons serve as ideal carriers due to their various properties for encoding information and minimal environmental interaction, making them vital for the global internet. High-dimensional and hyper-entanglement offer advantages over traditional two-mode encoding methods, including increase noise tolerance and information capacity. However, practical implementation is often limited by measurement device complexities and errors. Frequencies, or photon colours, present a promising approach to boost quantum communication thanks to their compatibility with existing telecommunications infrastructure and naturally occurs in photon pair generation. This thesis explores the frequency degree of freedom for applications in QKD, utilizing efficient all-fiber photon-pair sources to generate hyper-entangled states in polarization and frequency. The incorporation of fast modulators allows for high-speed operation while maintaining high entanglement fidelity. Reconfigurable spectral filters enable tailored spectro-temporal properties to fulfil requirements in multi-user networks and protocols beyond QKD, such as quantum secret sharing. To maximize quantum information capacity, methods for efficiently characterizing frequency entanglement are developed, achieving a certification of 35 modes, a record for the time and frequency degrees of freedom. Finally, estimates of secure key rates and a discussion of noise effects is shown. This foundation supports broadband and flexible quantum networks that effectively utilize frequency encoding in the future quantum internet.