Optimising entanglement distribution policies under classical communication constraints assisted by reinforcement learning

Machine Learning Science and Technology, vol. 6, pp. 035024

Abstract

Abstract Quantum repeaters play a crucial role in the effective distribution of entanglement over long distances. The nearest-future type of quantum repeater requires two operations: entanglement generation across neighbouring repeaters and entanglement swapping to promote short-range entanglement to long-range. For many hardware setups, these actions are probabilistic, leading to longer distribution times and incurred errors. Significant efforts have been vested in finding the optimal entanglement-distribution policy, i.e. the protocol specifying when a network node needs to generate or swap entanglement, such that the expected time to distribute long-distance entanglement is minimal. This problem is even more intricate in more realistic scenarios, especially when classical communication delays are taken into account. In this work, we formulate our problem as a Markov decision problem and use reinforcement learning (RL) to optimise over centralised strategies, where one designated node instructs other nodes which actions to perform. Contrary to most RL models, ours can be readily interpreted. Additionally, we introduce and evaluate a fixed local policy, the ‘predictive swap-asap’ policy, where nodes only coordinate with nearest neighbours. Compared to the straightforward generalisation of the common swap-asap policy to the scenario with classical communication effects, the ‘wait-for-broadcast swap-asap’ policy, both of the aforementioned entanglement-delivery policies are faster at high success probabilities. Our work showcases the merit of considering policies acting with incomplete information in the realistic case when classical communication effects are significant.

Authors 6

1. J Li Aachen Instituut-Lorentz 〈aQaL〉 Applied Quantum Algorithms

   Leiden University · Leiden University Medical Center

   Affiliation as printed

   Instituut-Lorentz, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

   〈aQaL〉 Applied Quantum Algorithms, Leiden, The Netherlands

2. Tim Coopmans Aachen 〈aQaL〉 Applied Quantum Algorithms

   Leiden University · Leiden University Medical Center · QuTech · Delft University of Technology

   Affiliation as printed

   EEMCS, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands

   LIACS, Universiteit Leiden, Niels Bohrweg 1, 2333 CA Leiden, The Netherlands

   QuTech, Delft University of Technology, Lorentzweg 1, 2628 CJ Delft, The Netherlands

   〈aQaL〉 Applied Quantum Algorithms, Leiden, The Netherlands

3. Patrick Emonts Aachen Instituut-Lorentz 〈aQaL〉 Applied Quantum Algorithms

   Leiden University · Universität Ulm · Leiden University Medical Center · Center for Integrated Quantum Science and Technology

   Affiliation as printed

   Center for Integrated Quantum Science and Technology (IQST), Ulm-Stuttgart, Germany

   Institute for Complex Quantum Systems, Ulm University, 89069 Ulm, Germany

   Instituut-Lorentz, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

   〈aQaL〉 Applied Quantum Algorithms, Leiden, The Netherlands

4. Kenneth Goodenough

   University of Massachusetts Amherst

   Affiliation as printed

   Manning College of Information and Computer Sciences, University of Massachusetts Amherst, 140 Governors Dr, Amherst, MA 01002, United States of America

5. Jordi Tura Aachen Instituut-Lorentz 〈aQaL〉 Applied Quantum Algorithms

   Leiden University · Leiden University Medical Center

   Affiliation as printed

   Instituut-Lorentz, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands

   〈aQaL〉 Applied Quantum Algorithms, Leiden, The Netherlands

6. Evert van Nieuwenburg Aachen 〈aQaL〉 Applied Quantum Algorithms

   Leiden University · Leiden University Medical Center

   Affiliation as printed

   LIACS, Universiteit Leiden, Niels Bohrweg 1, 2333 CA Leiden, The Netherlands

   〈aQaL〉 Applied Quantum Algorithms, Leiden, The Netherlands