Abstract
Quantum communication networks enable applications ranging from highly secure communication to clock synchronization and distributed quantum computing. Miniaturized, flexible, and cost-efficient resources will be key elements for ensuring the scalability of such networks as they progress towards large-scale deployed infrastructures. Here, we bring these elements together by combining an on-chip, telecom-wavelength, broadband entangled photon source with industry-grade flexible-grid wavelength division multiplexing techniques, to demonstrate reconfigurable entanglement distribution between up to 8 users in a resource-optimized quantum network topology. As a benchmark application we use quantum key distribution, and show low error and high secret key generation rates across several frequency channels, over both symmetric and asymmetric metropolitan-distance optical fibered links and including finite-size effects. By adapting the bandwidth allocation to specific network constraints, we also illustrate the flexible networking capability of our configuration. Together with the potential of our semiconductor source for distributing secret keys over a 60 nm bandwidth with commercial multiplexing technology, these results offer a promising route to the deployment of scalable quantum network architectures.
Highlights
Quantum technologies have the potential to enhance in an unprecedented way the security of communications across network infrastructures
Note that two different frequency demultiplexing/multiplexing approaches can be implemented, depending on the spectral region of interest: in the telecom C-Band (1530–1565 nm) we use a wavelength selective switch (WSS) and in the L-Band (1565–1625 nm) a coarse wavelength division multiplexing unit (CWDM) with 13 nm wide channels followed by a tunable filter
We have demonstrated a scalable approach to a fully connected entanglement distribution network using an AlGaAs chip emitting broadband polarization-entangled photon pairs in the telecom band
Summary
Quantum technologies have the potential to enhance in an unprecedented way the security of communications across network infrastructures. We distribute entanglement using Flexgrid multiplexing based on WSS technology, which is the current industry standard in classical communications, and offers straightforward reconfigurability in terms of central frequency and channel bandwidth adjustment while displaying wavelengthinsensitive insertion loss and polarization independence. This allows us to show that each of the two-user links in a fully connected entangled network of 4, 5, or 8 users, can support highquality entanglement distribution and efficient QKD at metropolitan scale distances. We demonstrate that the bandwidth reallocation enabled by the WSS can be used to equilibrate the resulting rates, materializing an elastic network
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