Quantum Internet: a step closer

Abstract

The Quantum Internet is a complementary tool to the widely spread classical Internet, which has already revolutionized our everyday life. The promise is that the Quantum Internet will unlock new unprecedented capabilities and applications that span from secure communication, to distributed quantum computation and enhanced quantum sensing. The realization of such a powerful tool is the result of a joint effort among several fields, like computer science, physics, engineering, and materials science, which all rely on the fundamentals of quantum mechanics. The introduction of a new computational unit, the qubit, allows for the creation of superposition and entangled states, and the possibility of measuring such states. On a practical level, we can envision the Quantum Internet as a network of interconnected heterogeneous platforms aimed at solving different tasks, such as the processing of quantum information at the end nodes, and the storing and retrieval of quantum information in between end nodes to bridge long distances. The quantum information routing is governed and optimized by a dedicated software architecture that facilitates the user interface, removing the requirement of knowing the hardware’s physical principles for a general user.
In the hardware framework, the Nitrogen-Vacancy center in diamond represents a viable platform as processing end node, thanks to the high quality of its qubits and the capability of generating remote entanglement with other nodes in the network via its optical interface. These properties can be engineered to utilize the NV center as a test-bed for demonstrating crucial steps towards the Quantum Internet final goal.
We first employ a two-node NV quantum network in the laboratory to demonstrate the elementary building-blocks of distributed quantum computation: the generation of a distributed 4-partite Greenberger-Horne-Zeilinger state and the realization of a non-local Controlled-NOT gate between physically separated and non-interacting qubits.
In the long distance scenario, we use the NV center platform to study the photonic interface of solid-state qubits with time-bin qubits compatible with the emission from quantum memory platforms, such as Rubidium gas or Thulium-doped crystals. The interface is benchmarked with a quantum teleportation experiment. Quantum teleportation is the ultimate protocol that enables the transfer of quantum information from one physical point to another. We teleport a photonic time-bin qubit to the communication qubit of the NV center platform, establishing the primary form of communication between heterogeneous platforms in a quantum network.
Finally, the two-node NV network is used as reliable setup to demonstrate the first operating system for quantum network applications, QNodeOS. QNodeOS can schedule and manage quantum network applications in a multitasking fashion. It constitutes a software interface which enables facilitated access for users, boosting the research in quantum network applications and making a first step towards the deployment of such technology into society.