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Impact of multimode sources on ensemble-based quantum repeaters

Emil R. Hellebek* and Anders S. Sørensen

  • *Contact author: Emil.hellebek@nbi.ku.dk
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Phys. Rev. Research 8, 033026 – Published 6 July, 2026

DOI: https://doi.org/10.1103/2pp6-tzx1

Abstract

Long-distance entanglement generation at a high rate is a major quantum technological goal yet to be fully realized, with the promise of many interesting applications, such as secure quantum computing on remote servers and quantum cryptography. One possible implementation is using a variant of the scheme proposed by Duan, Lukin, Cirac, and Zoller (DLCZ) [Duan et al., Nature (London) 414, 413 (2001)] by combining atomic-ensemble memories and linear optics with spontaneous parametric down-conversion (SPDC) sources. As we edge closer to the realization of such a technology, the complete details of the underlying components become crucial. In this paper, we consider the impact of the multimode emission from the SPDC source on quantum repeaters based on the DLCZ scheme. We consider two cases, driving the SPDC using short Gaussian pulses and driving the SPDC continuously. For pulsed driving, we find that the use of very narrow laser pulses to drive the SPDC source is crucial to obtain high-fidelity end-to-end entangled states, but this puts demands on the peak intensity. By introducing a maximally allowed laser intensity, we find optimal pulse widths for each swap depth. For continuous driving, we find the temporal acceptance window of clicks relative to the heralding time to be a crucial parameter, and we can similarly optimize the acceptance window for each swap depth. For both cases, we thus identify optimal parameters given experimental limitations and aims. We have thus provided helpful knowledge toward the realization of long-distance entanglement generation using the DLCZ scheme.

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Phys. Rev. Research 8, 033026– Published 6 July, 2026
  • Received 1 December 2025
  • Accepted 1 April 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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