Quantum repeaters memory size affects network performance
Performance Evaluation of Emerging Networks of Quantum Repeaters: Analysis and Simulation
Networking and Internet Architecture
Summary
Quantum networks need devices called repeaters to send information reliably over long distances. The authors studied a type of repeater called Dual Input Repeater (DIR) and measured how well networks with these work, focusing on how many memory slots each repeater needs. They found that even small memory sizes are enough for good performance most of the time, but there is a minimum memory size required to make entangled pairs successfully. Their work helps understand how network size, connection length, and errors impact repeater memory needs and overall performance.
What this means in practice
- •For quantum network operators: Design memory resources in quantum repeaters to achieve reliable entanglement distribution in experimental fiber-based quantum networks.
- •For telecommunications infrastructure planners: Assess how fiber lengths and network size affect quantum repeater memory to enable future quantum communication services over existing telecom fibers.
Authors
Kobi Ravid, Javad Ghaderi, Gil Zussman
Abstract
Emerging experimental quantum network deployments are based on collaborations between research institutions and rely on telecommunications fiber infrastructure. Currently, such networks consist of mostly Dual Input Repeaters (DIRs) and can be viewed as composed of (mostly) line graphs. In order to evaluate the performance of such networks (e.g., in terms of Entangled Pair Rate, EPR, and average Fidelity) we developed a custom quantum network simulation platform that takes into account both the quantum and classical network components. To support the verification of the simulation results, we develop a novel approach for performance analysis of DIRs. We compare the simulation results to the analytical results for DIRs and to prior results for repeaters with more than two inputs. We observe that although the expected memory utilization cannot be bounded, \emph{a small DIR memory size is sufficient and leads to minimal performance degradation}. For line networks with a single repeater and $3$ repeaters, we explore the dependency of incoming and outgoing memory size requirements on the number of nodes (network size), their connectivity (fiber length) and various quantum error settings (amplitude damping and phase flip channels). We evaluate the \emph{EPR} and the \emph{average Fidelity} for a sub-network of a deployed network with $3$ repeaters, using two alternative paths. We show that as the number of nodes increases or when the fiber lengths between nodes differ significantly, additional node memory is needed to maintain the same EPR (qubits are stored for longer duration to allow completion of entanglement across the network). We also show that the memory size should be above some minimum threshold to allow EP creation (EPR $>0$) as pair selection and swapping completion propagate across the network.