Optimizing repeater schemes for the quantum internet

Abstract

The rate at which quantum communication tasks can be performed using direct transmission is fundamentally hindered by the channel loss. Quantum repeaters allow one, in principle, to overcome these limitations, but their introduction necessarily adds an additional layer of complexity to the distribution of entanglement. This additional complexity-along with the stochastic nature of processes such as entanglement generation, Bell swaps, and entanglement distillation-makes finding good quantum repeater schemes nontrivial. We develop an algorithm that can efficiently perform a heuristic optimization over a subset of quantum repeater schemes for general repeater platforms. We find a strong improvement in the generation rate in comparison to an optimization over a simpler class of repeater schemes based on BDCZ (Briegel, Dür, Cirac, Zoller) repeater schemes. We use the algorithm to study three different experimental quantum repeater implementations on their ability to distribute entanglement, which we dub information processing implementations, multiplexed elementary pair generation implementations, and combinations of the two. We perform this heuristic optimization of repeater schemes for each of these implementations for a wide range of parameters and different experimental settings. This allows us to make estimates on what are the most critical parameters to improve for entanglement generation, how many repeaters to use, and which implementations perform best in their ability to generate entanglement.

Optimizing entanglement generation and distribution using genetic algorithms

“…We have introduced a methodology for the optimization of entanglement generation and distribution in repeater chains using GAs. In contrast with previous work in this area [18][19][20][21][22], our methodology is systematic, modular and broadly applicable. We validated it by benchmarking our GAs on functions commonly used for this purpose and by applying it to a repeater chain generating Werner states.…”

“…This allows us to answer questions such as what are the worst possible repeaters satisfying target benchmarks. Contrasting with previous work on repeater chain optimization [18][19][20][21][22][23], our methodology constitutes a systematic and modular approach to this problem, successfully integrating simulation and optimization tools, as well as allowing for the use of high-performance computing (HPC) clusters. A high-level overview of how a user interfaces with this process is shown in figure 1.…”

Protocols for Creating and Distilling Multipartite GHZ States With Bell Pairs

“…Ideally, we would consider all possible ways of distributing the Bell pairs over the network parties, and all possible combinations of the operations from Section III. Unfortunately, the number of these combinations grows superexponentially in n (see [40] for a similar argument). This makes a brute-force approach infeasible for relevant values of (n, k)-in particular, for the protocols described in Section IV: (n, k) = (4, 22) and (n, k) = (4, 42).…”

“…This makes a brute-force approach infeasible for relevant values of (n, k)-in particular, for the protocols described in Section IV: (n, k) = (4, 22) and (n, k) = (4, 42). For this reason, similar to the approaches in [40] and [41] for Bell pair distribution in the context of quantum repeater chains, we propose heuristic dynamic programs for optimizing the distribution of GHZ states.…”

Policies for elementary links in a quantum network

“…Typically, these works have been focused primarily on the topology of a linear chain of nodes. However, more recent work [66,78,79,[114][115][116][117][118][119][120][121][122][123] has begun to focus on arbitrary topologies, with routing protocols taken into account in some cases [56,57,89,90,[124][125][126][127]. The techniques used in these works are often varied, and sometimes different terminology and mathematical tools are used.…”