Resource Allocation for Rate and Fidelity Maximization in Quantum Networks

Existing classical optical network infrastructure cannot be immediately used for quantum network applications due to photon loss. The first step towards enabling quantum networks is the integration of quantum repeaters into optical networks. However, the expenses and intrinsic noise inherent in quantum hardware underscore the need for an efficient deployment strategy that optimizes the allocation of quantum repeaters and memories. In this paper, we present a comprehensive framework for network planning, aiming to efficiently distributing quantum repeaters across existing infrastructure, with the objective of maximizing quantum network utility within an entanglement distribution network. We apply our framework to several cases including a preliminary illustration of a dumbbell network topology and real-world cases of the SURFnet and ESnet. We explore the effect of quantum memory multiplexing within quantum repeaters, as well as the influence of memory coherence time on quantum network utility. We further examine the effects of different fairness assumptions on network planning, uncovering their impacts on real-time network performance.Comment: 18 pages, 8 figures, 3 appendice

Applications of Quantum Optics: From the Quantum Internet to Analogue Gravity

The aim of this thesis is to highlight applications of quantum optics in two very distinct fields: space-based quantum communication and the Hawking effect in analogue gravity. Regarding the former: We simulate and analyze a constellation of satellites, equipped with entangled photon-pair sources, which provide on-demand entanglement distribution ser- vices to terrestrial receiver stations. Satellite services are especially relevant for long-distance quantum-communication scenarios, as the loss in satellite-based schemes scales more favor- ably with distance than in optical fibers or in atmospheric links, though establishing quantum resources in the space-domain is expensive. We thus develop an optimization technique which balances both the number of satellites in the constellation and the entanglement-distribution rates that they provide. Comparisons to ground-based quantum-repeater rates are also made. Overall, our results suggest that satellite-based quantum networks are a viable option for establishing the backbone of future quantum internet. Regarding the latter: The Hawking effect was discussed in the astrophysical context of the spontaneous decay of black holes into blackbody radiation, i.e. Hawking radiation. However, this effect seems to be universal, appearing anywhere that an event horizon (a region which restricts the flow of information to one direction) forms. Here, we analyze the Hawking effect in an optical-analogue gravity system, building on prior theoretical results regarding this effect in dielectric media. We provide a simplification of the process via the Bloch- Messiah decomposition, which allows us to decompose the Hawking effect into a discrete set of elementary processes. With this simplification and utilizing a popular entanglement measure (the logarithmic negativity), we examine the quantum correlations of the stimulated Hawking effect, explicitly showing that an environmental background temperature, along with backscattering, can lead to entanglement “sudden-death , even when the number of entangled Hawking-pairs is comparatively large. We also discuss the prospect of enhancing and “reviving entanglement using single-mode, non-classical resources at the input. Though much of the discussion is phrased in terms of an optical-analogue model, the methods used and results obtained apply just as well to a variety of other systems supporting this effect. Finally, we provide decompositions of more exotic scenarios consisting of e.g. a white-hole– black-hole pair which share an interior region

Toward Photon-Efficient Key Distribution over Optical Channels

This work considers the distribution of a secret key over an optical (bosonic) channel in the regime of high photon efficiency, i.e., when the number of secret key bits generated per detected photon is high. While in principle the photon efficiency is unbounded, there is an inherent tradeoff between this efficiency and the key generation rate (with respect to the channel bandwidth). We derive asymptotic expressions for the optimal generation rates in the photon-efficient limit, and propose schemes that approach these limits up to certain approximations. The schemes are practical, in the sense that they use coherent or temporally-entangled optical states and direct photodetection, all of which are reasonably easy to realize in practice, in conjunction with off-the-shelf classical codes.Comment: In IEEE Transactions on Information Theory; same version except that labels are corrected for Schemes S-1, S-2, and S-3, which appear as S-3, S-4, and S-5 in the Transaction