Wireless quantum key distribution in indoor environments

Abstract

We propose and study the feasibility of wireless quantum key distribution (QKD) in indoor environments. Such systems are essential in providing wireless access to the developing quantum communications networks. We find a practical regime of operation, where, in the presence of external light sources and loss, secret keys can be exchanged. Our findings identify the trade-off between the acceptable amount of background light and the receiver field of view, where the latter specifies the type of equipment needed for the end user and its range of movements. In particular, we show that, using a proper setting, we can provide mobility for the QKD users without imposing stringent conditions on beam steering.Index Terms-BB84, decoy states, optical wireless communications (OWC), Quantum key distribution (QKD). I. INTRODUCTIONQ UANTUM key distribution (QKD) is a promising technology for achieving security in the quantum era [1]. It provides a secure way of distributing secret keys between two users over an optical channel [2], [3]. The security is guaranteed by the properties of quantum mechanics rather than computational complexity [4]. The latter is at the core of public key cryptography schemes, whose security is threatened by advanced algorithms that can be run on quantum computers [5], [6], [7], [8]. QKD offers a solution to this problem and will possibly be the most imminent application of quantum technologies in our daily life. It is important to utilize the advantages of this scheme not only in niche markets but also for the general public [9], [10]. This necessitates developing hybrid quantum-classical networks that support many users. This requires revisiting the requirements at both access and core parts of the network. This work focuses on the access networks, and, in particular, it addresses the wireless mode of access in indoor environments for such QKD networks. This would resemble a quantum Li-Fi system, possibly, in parallel with a classical Li-Fi, that enables end users to exchange secret keys with other network users in a convenient way [11].The current dominant approach for ensuring data security over the Internet is based on a combination of public-key cryptography, e.g. the RSA protocol [12], for exchanging a secret key/seed, and symmetric-key cryptography protocols, such as advanced encryption standard (AES) or secure hash algorithm, for encryption, decryption, and authentication. The security of RSA is, however, based on the computational complexity of the factoring problem. The latter does not have any known This work was presented in part at the IEEE Globecom Conf. 2015 held in San Diego, CA. This research has partly been funded by the UK EPSRC Grants EP/M506953/1 and EP/M013472/1, and the ministry of higher education and scientific research in Libya. Both authors are with the

Quantum-classical access networks with embedded optical wireless links

“…The short answer turns out to be negative for setups 2-4. We already know the result for setup 1 from the previous work in [13], in which the authors show that, if the only source of lighting in the room is an LED bulb with a PSD on the order of 10 −5 -10 −6 W/nm, then there will be regions over which even in cases 1 and 2 the wireless user can exchange secret keys with the Rx box. This seems to no longer necessarily hold if we remove the trusted relay node in the room.…”

“…For our wireless user, we consider a particular indoor environment, in which it has been shown that wireless QKD is feasible [13], [14]. In this setting, a window-less room, of X × Y × Z dimensions, is lit by an artificial light source.…”

“…Below, the parameter values for each link will be calculated separately. Setup 1, wireless link: For the wireless channel, we assume that the background noise due to the artificial lighting source is denoted by n B1 , which can be calculated using the methodology proposed in [13]. In our calculations, we upper bound n B1 by considering the case where the QKD receiver is focused on the center of the room.…”

“…2. We neglect the impact of the ambient noise in our windowless room [13]. The total transmissivity is also given by η = H DC η d1 /2.…”

Quantification of the Impact of Photon Distinguishability on Measurement-Device- Independent Quantum Key Distribution

“…(10) Discard unusable trials and flip Bob's key bit in accordance with the results of step (9), retaining N sifted ≈ N raw /4 bits. (11) Compare Alice's and Bob's sifted keys to determine the QBER= N error /N sifted [18].…”