Rethinking Quantum Networking with Advances in Fiber Technology

Abstract

Recent comparisons of quantum repeater protocols have highlighted the strong near-term potential of multiplexed two-way architectures for long-distance quantum communication. At the same time, advances in hollow-core fiber (HCF) technology motivate a re-examination of the physical transmission medium as an architectural lever in quantum network design. In this work, we compare emerging anti-resonant HCFs against conventional silica single-mode fibers (SMFs) in multiplexed two-way quantum repeater networks. We evaluate their performance under both telecom and memory-native transmission, accounting for frequency-conversion overheads, coupling efficiencies, memory decoherence, and operational noise. We find that HCF significantly outperforms SMF across a wide range of regimes. With memory-native transmission, HCF yields up to an order of magnitude improvement in secret-key rate per channel use under realistic conversion efficiencies. Even at telecom wavelengths, HCF enables larger optimal repeater spacing, improving rate--cost tradeoffs and reducing repeater requirements. We further quantify the role of memory quality, hardware efficiency, detector and conversion losses, and two-qubit gate noise in shaping these gains. These results show that recent advances in HCF materially expand the design space of practical terrestrial quantum repeater networks.

Figures (11)

• Figure 1: Physical-layer comparison of conventional silica single-mode fiber (SMF) and hollow-core fiber (HCF). (a) Cross section and fundamental guided mode of a step-index SMF. (b) Cross section and fundamental guided mode of a double-nested anti-resonant hollow-core fiber. (c) Propagation loss across relevant wavelengths for representative SMF and HCF technologies, using measured data from prior work Petrovich2025Sakr:21Adamu:24Sato24smfcorning_hi780_speccorning_smf28_productinfo and projected achievable performance from NumkamFokoua23hcfreview.
• Figure 2: Architecture for multiplexed entanglement generation and entanglement swapping between neighboring repeater nodes. Each node contains a register of quantum memories coupled to photonic emitters that generate photons entangled with the stored memory qubits. (A) Photons emitted from the memory register are coupled into the outgoing optical fiber with efficiency $\eta_{\mathrm{coupling,\,memory\rightarrow fiber}}$ and may undergo frequency conversion with efficiency $\eta_{\mathrm{memory\rightarrow trans\_f}}$ before transmission through the channel. (B) Photons arriving from the channel are coupled from the fiber into the receiver optics with efficiency $\eta_{\mathrm{coupling,\,fiber\rightarrow det}}$ and may undergo frequency conversion with efficiency $\eta_{\mathrm{trans\_f\rightarrow det}}$ before detection with detector efficiency $\eta_{\mathrm{det}}$. Photons from neighboring nodes interfere at the midpoint Bell-state analyzer (BSA) array. Successful Bell-state measurements herald the creation of entanglement between remote memory qubits stored in the two nodes. Classical signals from the BSA are communicated back to the nodes via a two-way classical channel to identify successful entanglement events. Once entanglement is established, repeaters perform performs the entanglement swapping (E.S.) operations to propagate the link.
• Figure 3: Time evolution of the nested entanglement swapping protocol used to extend entanglement across a chain of repeater nodes. Elementary links of length $L_0$ are first generated between neighboring nodes. Once two adjacent elementary links are available, an entanglement swapping (E.S.) operation is performed at the intermediate repeater, creating a longer link of length $2L_0$. The same procedure is recursively applied: swapping operations at higher levels combine neighboring links to produce entangled connections of length $4L_0$, $8L_0$, and ultimately longer end-to-end links. The vertical axis represents time, illustrating that entanglement generation attempts occur in parallel across elementary links, while swapping operations are triggered whenever the required shorter links become available. Highlighted repeater modules indicate nodes where entanglement swapping operations are performed to extend the entanglement length.
• Figure 4: HCF and SMF optimal strategy across frequency conversion efficiency and inter-repeater spacing parameter space. Plots show the regions of the parameter space for which direct transmission at the quantum memory wavelength outperforms bi-directional frequency conversion. Darker regions for each plot indicate where direct transmission at 780 nm is optimal.
• Figure 5: Angle-dependent mode-match coupling efficiency $\eta_{\mathrm{opt}}(\theta)$ for conventional SMF at 1550 nm and DNANF designs at 1550 nm and 780 nm. Angular misalignment is modeled as a tilt by $\theta$ in the $x$--$z$ plane. The non-tapered DNANF shows reduced angle tolerance due to its larger core, while adiabatically tapered end facets improve tolerance and approach SMF performance.