Multiplexing and entanglement of solid-state quantum memories for intercity quantum networks

DIPC Seminars

Speaker

Markus Teller
ICFO

When

2026/02/05
12:00

Place

DIPC Josebe Olarra Seminar Room

Host

Ricardo Diez Muino

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A long-distance quantum internet requires quantum repeaters dispersed between the end nodes for distributing entanglement across the network. Successful entanglement events are heralded by detections at intermediate stations placed between the nodes. However, in a sequence of entanglement generation attempts, the repeater nodes must wait for the heralding signal to return from the intermediate station before the next attempt. At intercity distances, the entanglement rate may consequently be limited by the time it takes for the photon to travel and the time required for classical communication. Quantum repeaters based on rare-earth-doped crystals overcome this limitation, as their high degree of multiplexing allows for generating entanglement sequentially in different degrees of freedom or modes, such as time, frequency, and space. Thus, the entanglement rate increases linearly with the available number of modes.

In this talk, I will present experimental efforts towards the entanglement of two multiplexed quantum memories across the metropolitan network of Barcelona. First, I will discuss our recent in-lab demonstration of entanglement of two spin-wave quantum memories. Then, I will turn to experiments with a novel array of ten fully-controllable quantum memories, which promises high entanglement distribution rates through its combination of spatial and temporal multiplexing. We demonstrate quantum storage in 250 spatio-temporal modes and non-classical correlations between the quantum memories and telecom photons detected after 40km of deployed fiber across the metropolitan area. Lastly, we store qubits in the path and time degrees of freedom and perform full-state tomography of the retrieved states. In the future, this system may be combined with sources of photonic cluster states, and the demonstrated control may enhance the computational power of these photonic quantum processors.