For imparting data security to the end-users in a archetypal fiber-to-the-home (FTTH) network, quantum cryptography (QC) is getting much attention now-a-days. QC or more specifically quantum key distribution (QKD) promises unconditionally secure protocol, the Holy Grail of communication and information security, that is based on the fundamental laws of quantum physics. In this talk, we will discuss our latest experiments on a four-state (Quadrature Phase Shift Keying `QPSK') RF sub-carrier assisted continuous-variable quantum key distribution (CV -QKD) multi-user network based on ultra low loss quantum channel (pure silica core fiber `PSCF') and micro-electromechanical systems (MEMS) based add/drop switch. A coherent receiver with local local oscillator (LLO) is implemented, which ideally could not be accessed by eavesdroppers (Eve), aided with digital signal processing (DSP) module for phase noise cancellation (PNC). With 10 Gbit/s QPSK classical WDM signals, we have recorded secure key rates of 8.65 Mbit/s over 20 km and upto 12 Mbit/s over lossless channel. The experimental setup is further extended to a optically switched multi-user network, i.e. multiple Bobs, for implementing add/drop operations to achieve key rates of 5.98 Mbit/s for a 2_2 MEMS switch. It is expected that the proposed cost-effective and energy efficient QKD network can facilitate the practical application of the CV-QKD protocol on commercial scale in near future for smart access networks.
For imparting data security to the end-users in a archetypal fiber-to-the-home (FTTH) network, quantum cryptography (QC) is getting much attention now-a-days. QC or more specifically quantum key distribution (QKD) promises unconditionally secure protocol, the Holy Grail of communication and information security, that is based on the fundamental laws of quantum physics. In this talk, we will discuss our latest experiments on a four-state (Quadrature Phase Shift Keying QPSK') RF sub-carrier assisted continuous-variable quantum key distribution (CV -QKD) multi-user network based on ultra low loss quantum channel (pure silica core fiber PSCF') and micro-electromechanical systems (MEMS) based add/drop switch. A coherent receiver with local local oscillator (LLO) is implemented, which ideally could not be accessed by eavesdroppers (Eve), aided with digital signal processing (DSP) module for phase noise cancellation (PNC). With 10 Gbit/s QPSK classical WDM signals, we have recorded secure key rates of 8.65 Mbit/s over 20 km and upto 12 Mbit/s over lossless channel. The experimental setup is further extended to a optically switched multi-user network, i.e. multiple Bobs, for implementing add/drop operations to achieve key rates of 5.98 Mbit/s for a 2_2 MEMS switch. It is expected that the proposed cost-effective and energy efficient QKD network can facilitate the practical application of the CV-QKD protocol on commercial scale in near future for smart access networks.
For secure data transmission to the end users in a conventional fiber-to-the-home (FTTH) network, quantum cryptography (QC) is getting much consideration nowadays. QC or more specifically quantum key distribution (QKD) promises unconditionally secure protocol, the Holy Grail of communication and information security that is based on the fundamental laws of quantum physics. In this chapter, we discuss the design issues in a hybrid quantum-classical communication network, performance of the cost-effective off-the-shelf telecommunication equipment, our latest results on a four-state (Quadrature Phase Shift Keying, ‘QPSK’) RF sub-carrier assisted continuous-variable quantum key distribution (CV-QKD) multiuser network based on ultra-low loss quantum channel (pure silica core fiber, ‘PSCF’) and microelectromechanical systems (MEMS) based add/drop switch. The results are thoroughly compared with the commercially available high-cost encryption modules. It is expected that the discussed cost-effective and energy efficient QKD network can facilitate the practical applications of the CV-QKD protocol on the commercial scale in near future for smart access networks.
There is current significant interest in Fiber-to-the-Home (FTTH) networks, that is, end-to-end optical connectivity. Currently, it may be limited due to the presence of last-mile copper wire connections. However, in near future, it is envisaged that FTTH connections will exist, and a key offering would be the possibility of optical encryption that can best be implemented using Quantum Key Distribution (QKD). However, it is very important that the QKD infrastructure is compatible with the already existing networks for a smooth transition and integration with the classical data traffic. In this paper, we report the feasibility of using off-the-shelf telecommunication components to enable high performance Continuous Variable-Quantum Key Distribution (CV-QKD) systems that can yield secure key rates in the range of 100 Mbits/s under practical operating conditions. Multilevel phase modulated signals ( m -PSK) are evaluated in terms of secure key rates and transmission distances. The traditional receiver is discussed, aided by the phase noise cancellation based digital signal processing module for detecting the complex quantum signals. Furthermore, we have discussed the compatibility of multiplexers and demultiplexers for wavelength division multiplexed Quantum-to-the-Home (QTTH) network and the impact of splitting ratio is analyzed. The results are thoroughly compared with the commercially available high-cost encryption modules.
Data encryption is gaining much attention these days from the research community and industry for transmitting secure information over access networks, i.e. `fiber-to-the-home (FTTH)' networks and data centers. It is important that the newly designed encrypted networks are fully functional, reconfigurable, compatible, flexible and scalable with the existing deployed optical fiber networks around the globe. The prime benefit of having FTTH networks is the optical end-to-end data encryption that can best be implemented by quantum-keydistribution (QKD) protocols using state-of-the-art telecommunication components, i.e. continuous-variable quantum key distribution (CV-QKD). In this paper, we numerically investigate the quadrature phase shift keying (QPSK) based CV-QKD network that is compatible with the next generation (NG) services such as point-to-point (P2P) transmission and multicast overlay (MCO) traffic for audio/video signalling. We have further investigated the performance of quantum signals on multi-user fibers by emulating 7-, 12- and 19-core multi-core fibers (MCF). 100 Mbits/s secure key rates (SKRs) can be generated for inter-core crosstalk (XT) values of <; -20 dB. These results and theoretical framework will allow the telecommunication industry to extend these scenarios not only to accommodate more complex trust constraints, but also to take into account the robustness and resiliency of a complex encrypted network.
Quantum key distribution (QKD) systems have already attained much attention for providing end-to-end data encryption to the subscribers. However, it is very important that the QKD infrastructure is compatible with the already existing telecommunication networks for a smooth transition and integration with the classical data traffic. Optical fibers and commercially available transceivers are the key element for implementing the quantum network because of the strong dependence of secure key rate on the loss budget and excess noise. In this paper, we report the feasibility of using off-the shelf telecommunication components to enable high performance Continuous-Variable Quantum Key Distribution (CV-QKD) systems that can yield secure key rates in the range of 100 Mbit/s under practical operating conditions. Classical multilevel phase modulated signals (m-PSK) are evaluated in-terms of secure key generation and transmission distance when they are implemented and detected with classical coherent receiver. The traditional receiver is discussed, aided by the phase noise cancellation based digital signal processing module for detecting the complex quantum signals. Furthermore, we have discussed the compatibility of multiplexers and de-multiplexers for wavelength division multiplexed quantum-to-the-home (QTTH) network.
Continuous-variable quantum key distribution (CV-QKD) is a promising solution for providing high secure key rates in moderate loss channels. A great advantage with respect to discrete-variable (DV) systems is the use of a technology similar to the one used in classical coherent communication, in particular for the detection system, which can operate at room temperature and benefits from an easier integration process. In addition to this, the use of advanced digital signal processing (DSP) techniques developed for classical communication allows for bandwidth-efficient temporal shaping, which optimizes the performance of the CV-QKD system. These techniques applied to the detected signal are also fundamental for using a locally generated local oscillator, correcting frequency and phase differences using frequency-multiplexed pilots generated by the transmitter. In this presentation, we will describe how these DSP techniques can be applied to a CV-QKD system and show some recent experimental results obtained by our research group, including results for a receiver based on a Photonic Integrated Circuit (PIC).
Quantum secure communication technology, grounded in the principles of quantum mechanics, has revolutionized traditional cryptographic methods, which predominantly rely on mathematical algorithms and logical transformations. Quantum key distribution (QKD) facilitates the secure sharing of symmetric keys between legitimate parties, ensuring the integrity and confidentiality of information in communication channels. Among various QKD schemes, continuous variable quantum key distribution (CV-QKD) has emerged as a viable alternative to the more established discrete variable quantum key distribution (DV-QKD). CV-QKD boasts several advantages, including straightforward deployment, reduced operational costs, and stable signal quality, positioning it as a significant component of the quantum communication landscape. Quantum noise stream cipher (QNSC) represents a technique that employs redundant data streams to encrypt plaintext. Notably, QNSC shares structural similarities with the optical path used in quantum key distribution, allowing for compatibility with existing QKD infrastructure. Furthermore, the keys generated through quantum key distribution ensure absolute security, enabling them to substitute the data streams produced by pseudo-random sequences traditionally used in classical encryption schemes. This substitution enhances the overall security framework of the quantum noise stream encryption approach. The quantum access network (QAN) extends quantum key distribution capabilities from point-to-point connections to point-to-multipoint configurations, thereby becoming an essential component of contemporary network architectures. By interlinking multiple end users with a network backbone, quantum access networks can seamlessly integrate with quantum key distribution protocols. This integration offers a cost-effective and scalable solution for user access to the network. Extensive experimental verifications have demonstrated the viability of downstream access networks, indicating that the merging of quantum access network structures with quantum stream encryption technologies can yield a comprehensive quantum experimental platform. On this platform, security keys are derived through quantum key distribution, which subsequently facilitates the encryption of plaintext information. Notably, experimental validations involving eight users have been successfully executed on this platform, underscoring its practical applicability and effectiveness.