The finite-key effects in quantum access networks are studied. We consider a quantum-classical network where each user is equipped with a certain wavelength to exchange secure keys, using quantum key distribution techniques, and another one to exchange classical data. Users are connected to the central office via a passive optical network. The quantum users are connected to the fiber links via an indoor wireless channel. We investigate the regimes of operation within which a secure key can be exchanged in a reasonable amount of time. We find out that by properly designing the system, it is possible to run both quantum and classical systems at their full capacity.
The finite-key effects in quantum access networks are studied. We consider a quantum-classical network where each user is equipped with a certain wavelength to exchange secure keys, using quantum key distribution techniques, and another one to exchange classical data. Users are connected to the central office via a passive optical network. The quantum users are connected to the fiber links via an indoor wireless channel. We investigate the regimes of operation within which a secure key can be exchanged in a reasonable amount of time. We find out that by properly designing the system, it is possible to run both quantum and classical systems at their full capacity.
We investigate the use of high-dimensional quantum key distribution (HD-QKD) for wireless access to hybrid quantum-classical networks. We used-dimensional time-phase encoded states to exchange a secret key between an indoor wireless user and the central office on the other end of the access network. We evaluate the performance in the case of transmitting quantum and classical signals over the same passive optical network by accounting for the impact of background noise induced by the Raman-scattered light on the QKD receiver. We also take into account the loss and background noise that occur in indoor environments as well as finite key effects in our analysis. By studying the system under nominal simulation conditions, we identify regimes of operation in which an HD-QKD system withd=4can outperform its qubit-based counterpart.
We propose a low-complexity near-optimal wavelength allocation technique for quantum key distribution access networks that rely on wavelength division multiple access. Such networks would allow users to send quantum and classical signals simultaneously on the same optical fiber infrastructure. Users can be connected to the access network via optical wireless or wired links. We account for the background noise present in the environment, as well as the Raman noise generated by classical channels, and calculate the secret key generation rate for quantum channels in the finite-key setting. This allows us to examine the feasibility of such systems in realistic scenarios when the secret key exchange needs to be achieved in a limited time scale. Our numerical results show that, by proper choice of system parameters for this noisy system, it is possible to exchange a secret key in tens of seconds. Moreover, our proposed algorithm can enhance the key rate of quantum channels, especially in high noise and/or high loss regimes of operation.
Among all emerging quantum information technologies, quantum key distribution (QKD) is one of the most developed techniques. QKD harnesses the intrinsic laws of quantum mechanics to provide a method for distributing secret random keys, which can be used for data encryption and decryption between two intended users. QKD has already been demonstrated in different scenarios over optical fibre and in atmospheric channels. QKD has also been used for security assurance in several network settings, in addition of being commercially available today. Despite remarkable progress in QKD systems, convenient access to the developing quantum communications networks is still missing. Adopting QKD in mobile devices would enable such a service, particularly, in indoor environments. This is in line with the recent advancement in fabricating microchip-scale QKD devices, which would ease this incorporation into mobile devices. This work focuses on the access networks, and, in particular, it addresses the wireless mode of access in indoor environments for QKD networks. We find a practical regime of operation, where, in the presence of external light sources and loss, secret keys can be exchanged. We then propose practical configurations that would enable wireless access to hybrid quantum-classical networks. The proposed setups would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. We account for adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to the transmission of both quantum and classical signals over the same fibre. In addition, we consider the loss and the background noise that arise from indoor environments. We consider a number of discrete and continuous-variable QKD protocols and study their performance in different scenarios. In our analysis we consider the asymptotic scenario, as well as the finite-size key effects. In the former case, an infinite number of signals are assumed to be exchanged between the sender and the recipient, whereas in the latter, which represents the
practical scenario, a finite number of signals are exchanged between the two users. Our results indicate that a feasible regime of operation for wireless QKD exists. This makes the QKD technologies available to end users of a communications network.
It is well known that optical access networks are able to provide high data rates over long distances and to a reasonable number of users. Security and privacy are always a challenge for public accessible network infrastructures. Especially in time-division multiplexing passive optical networks (TDM-PONs), in which the downstream signal is broadcasted to all users connected via the same wavelength channel in a shared fiber link, privacy can be a critical concern. Although encryption at the application layer can provide a high level of security, this can be achieved only if the encryption key distribution is perfectly save. On the other hand, encryption on the physical layer such as quantum cryptography or, more precisely, quantum key distribution (QKD) is a very promising approach to achieve secure communication. However, there remain several issues that have to be solved before the quantum cryptography reaches the maturity level needed for a cost effective implementation in practical networks. In this paper, we address quantum key distribution (QKD) over passive optical access networks, which is an enabling technology required to cost efficiently deploy practical quantum encrypted data communication in the access area. We study different methods to integrate QKD systems in conventional optical access networks and quantitatively evaluate their suitability for a potential implementation.
We examine the applicability of wireless indoor quantum key distribution (QKD) in hybrid quantum-classical networks. We propose practical configurations that would enable wireless access to such networks. The proposed scenarios would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. QKD signals, sent through wireless indoor channels, are combined with classical ones and sent over the same fiber link to the remote user. Dense wavelength-division multiplexing would enable the simultaneous transmission of quantum and classical signals over the same fiber. We consider the adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to such an integration. In addition, we consider the loss and the background noise that arise from indoor environments. Decoy-state BB84 and measurement device-independent protocols are employed for the secret key rate analysis.
We examine the applicability of wireless indoor quantum key distribution (QKD) in hybrid quantum-classical networks. We propose practical configurations that would enable wireless access to such networks. The proposed setups would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. QKD signals, sent through wireless indoor channels, are combined with classical ones and sent over shared fiber links to the remote user. Dense wavelengthdivision multiplexing would enable the simultaneous transmission of quantum and classical signals over the same fiber. We consider the adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to such an integration. In addition, we consider the loss and the background noise that arise from indoor environments. We consider a number of discrete and continuous-variable QKD protocols and study their performance in different scenarios.