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Quantum Internet Alliance

Periodic Reporting for period 1 - QIA (Quantum Internet Alliance)

Reporting period: 2018-10-01 to 2020-03-31

The European Quantum Internet Alliance (QIA) addresses the Quantum Flagship strategic objectives related to the development of entanglement-based networks by developing a Blueprint for a pan-European entanglement-based Quantum Internet. To achieve this goal, we designed an approach where we take into account the potential user demands of such a quantum internet and we push forward the development of hardware (end processing nodes, quantum repeaters) and software (efficient control plane and software stack) to enable quantum internet real-world applications. This is combined with a feasibility and scalability analysis based on the network requirements that can enable end-to-end qubit transmission. This Network Architecture Blueprint will give crucial insights into the relative importance of the different hardware parameters that will need to be optimised. As a final step we will perform an overall systems test (Blueprint demo) to demonstrate the integration between the combined hardware and software stack by executing a high-level application on a demonstration network connecting multiple network nodes.
The specific objectives of QIA are:

• To identify use cases and software embedding of quantum network applications

• To determine the parameter requirements for desired protocols to satisfy user demands

• To achieve the first demonstration of key enabling technologies for high-rate quantum repeaters

• To achieve the first demonstration of a quantum network stack providing the basis for scalable control of a Quantum Internet

• To develop the first multi-node (>2) networks linking few-qubit quantum processors

• To achieve the first demonstration of a universal software stack for a Quantum Internet that will make this network fully programmable

• To develop the first interface between high-speed repeater platforms and end-nodes

QIA is a synergetic collaboration between world-class academic partners and key industrial partners in all relevant disciplines and sectors, including physics (physical modelling, solid state experiment, quantum optics, atomic physics), engineering (optics engineering, material and components, infrastructure), computer science (software engineering, computer networks and quantum protocol design).
To identify use cases and software embedding of quantum network applications: We have created a Quantum Protocol Zoo, a repository of protocols for quantum networks that serves as a platform that enables experts from academia and industry to find real-life use cases for the listed protocols and at the same time innovate on (or compose) the existing ones to tailor-made new protocols for the desired task.

To determine the parameter requirements for desired protocols to satisfy user demands: We have set up a network simulation platform that includes the physical modelling of network components (processing nodes, repeaters, heralding stations, quantum memories, beamsplitters, detectors, fibres, photons) that will enable us to determine the parameter requirements for the desired protocols.

To achieve the first demonstration of key enabling technologies for high-rate quantum repeaters: We explore three different physical platforms to increase entanglement generation rates. Two of them (atomic ensembles and multiplexed solid-states quantum memories) are based on heralded entanglement of multiplexed quantum memories; the third one consists of a more exploratory approach based on the use of photonic quantum repeaters (third-generation quantum repeaters). During this period we have advanced the state of the art in efficiency, storage times, multiplexing. We have demonstrated entanglement between matter (a trapped ion) and light (a photon) over long distances.

To achieve the first demonstration of a quantum network stack providing the basis for scalable control of a Quantum Internet: We have proposed a functional allocation of a quantum network stack and constructed the first physical and link layer protocols that turn ad-hoc physics experiments producing heralded entanglement between quantum processors into a well-defined and robust service.

To develop the first multi-node (>2) networks linking few-qubit quantum processors: We have designed and implemented a novel architecture for phase stabilisation to enable scalability to multiple NV nodes. A third NV node has been built and made fully operational. We have also measured Hong-Ou-Mandel interference between photons from two ion-trap nodes, establishing that they are indistinguishable from one another, a requirement for establishing teleportation between the two remote nodes

To achieve the first demonstration of a universal software stack for a Quantum Internet that will make this network fully programmable: We have developed a universal software platform that allows writing of quantum network programs and protocols on different underlying hardware platforms and have successfully executed simple instructions on a single NV qubit.

To develop the first interface between high-speed repeater platforms and end-nodes: We have worked on approaches to link quantum processors and quantum repeaters using photon frequency conversion, to link their individual photon energies via a common telecom wavelength.
QIA work during this first period has contributed to various breakthroughs that will lay the basis for future quantum communication technologies:

o Entanglement between a trapped ion and a photon over 50 km of spooled optical fibre, a world record.

o First cavity-mediated photonic link between two remote ion traps, with preliminary results showing quantum interference between photons emitted by the distant nodes, and entanglement between two remote ions expected early in the second phase.

o Setup of the world’s first multi-node quantum network, with preliminary results showing entanglement across the two separate legs, and first entanglement between three quantum processor nodes expected early in the second phase

o First demonstration of a hybrid discrete-continuous quantum interface, a scientific breakthrough that provides a fundamentally new approach to network interfaces

o Full control and any-to-any pair-wise entanglement on a 10-qubit diamond chip, providing the largest solid-state spin-qubit processor reported to date and longest quantum state storage time of an individually addressable solid-state qubit (75 seconds).

o High efficiency quantum memory enabling storage and retrieval of photonic entanglement with 87 % efficiency, a world record.

o Long-lived solid-state quantum memory at single photon level with on demand read-out, with storage time of 20 ms, a 20-fold increase over the state-of the art.

o Massively multiplexed solid-state quantum memory combining spectral and temporal multiplexing, enabling storage of 135 discrete modes.

o One-way quantum repeaters scheme towards high speed quantum communication.

o First physical and link layer protocols .

o The world’s first platform-independent software stack that supports the execution of arbitrary applications and enables control of a Quantum Internet.

o Development of high-speed time tagging electronics (timing resolution 2.7 ps).

o Nnovel architecture for phase stabilization that enable netwrok scalability beyond 2 nodes.

o A laser for the narrow-band excitation of NV centers integrated into an external-cavity diode laser system with 1 kHz linewidth.
Quantum Internet, an artist's impression