How Many Qubits Can Be Teleported? Scalability of Fidelity-Constrained Quantum Applications

TL;DR

This paper investigates the scalability limits of quantum teleportation for multiple qubits in quantum networks, emphasizing the impact of memory coherence and entanglement generation on fidelity constraints.

Contribution

It introduces a reliability metric for multi-qubit teleportation and develops a Monte Carlo simulator to analyze scalability under various quantum link and memory types.

Findings

Memory coherence limits the number of qubits that can be reliably teleported.

Parallel entanglement generation is crucial for scaling multi-qubit teleportation.

Fidelity constraints significantly impact quantum network scalability.

Abstract

Quantum networks (QNs) enable qubit transfer between distant nodes through quantum teleportation, which reconstructs a quantum state at a remote node by consuming a shared Bell pair. In multi-qubit quantum applications (QApps), the teleported qubits may need to remain stored in quantum memories until execution can start, while decoherence progressively reduces their fidelity with respect to the ideal target state. Such QApps can operate only if all teleported qubits simultaneously satisfy a minimum fidelity threshold. In this paper, we study how many qubits can be teleported under this fidelity-constrained operation in a two-node QN. To this end, we define a QApp-level reliability metric as the probability that all end-to-end Bell pairs satisfy the target fidelity when the multi-qubit teleportation stage is completed. We then develop a Monte Carlo simulator that captures stochastic Bell-pair generation, Quantum Repeater (QR)-assisted entanglement distribution, and fidelity degradation. The analysis considers fiber-based and terrestrial free-space optical (FSO) quantum links, as well as representative NV-center- and trapped-ion-based quantum memories. Results show that memory coherence is the main scalability bottleneck under stringent fidelity targets, while parallel entanglement generation is essential for multi-qubit teleportation.