Kavli Affiliate: Stephanie Wehner
| First 5 Authors: Bethany Davies, Álvaro G. Iñesta, Stephanie Wehner, ,
| Summary:
Quantum networks crucially rely on the availability of high-quality entangled
pairs of qubits, known as entangled links, distributed across distant nodes.
Maintaining the quality of these links is a challenging task due to the
presence of time-dependent noise, also known as decoherence. Entanglement
purification protocols offer a solution by converting multiple low-quality
entangled states into a smaller number of higher-quality ones. In this work, we
introduce a framework to analyse the performance of entanglement buffering
setups that combine entanglement consumption, decoherence, and entanglement
purification. We propose two key metrics: the availability, which is the
steady-state probability that an entangled link is present, and the average
consumed fidelity, which quantifies the steady-state quality of consumed links.
We then investigate a two-node system, where each node possesses two quantum
memories: one for long-term entanglement storage, and another for entanglement
generation. We model this setup as a continuous-time stochastic process and
derive analytical expressions for the performance metrics. Our findings unveil
a trade-off between the availability and the average consumed fidelity. We also
bound these performance metrics for a buffering system that employs the
well-known bilocal Clifford purification protocols. Importantly, our analysis
demonstrates that, in the presence of noise, consistently purifying the
buffered entanglement increases the average consumed fidelity, even when some
buffered entanglement is discarded due to purification failures.
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