Quantum Internet and Security of Military Communications

In general, the Internet relies on complex codes to protect information, but hackers are becoming more adept at defeating such systems. These cyberattacks lead to privacy breaches of government officials, as well as large corporations, costing billions of euros per year in total and compromising customer data. According to ENISA reports, these numbers are set to rise. Quantum technology is seen by scientists as a revolutionary replacement for standard encryption techniques.

Geometric entanglement of a photon and spin qubits in diamond

Geometric nature, which appears in photon polarization, also appears in spin polarization under a zero magnetic field. These two polarized quanta, one travelling in vacuum and the other staying in matter, behave the same as geometric quantum bits or qubits, which are promising for noise resilience compared to the commonly used dynamic qubits. Here we show that geometric photon and spin qubits are entangled upon spontaneous emission with the help of the spin − orbit entanglement inherent in a nitrogen-vacancy center in diamond. The geometric spin qubit is defined in a degenerate subsystem of spin triplet electrons and manipulated with a polarized microwave. An experiment shows an entanglement state fidelity of 86.8%. The demonstrated entangled emission, combined with previously demonstrated entangled absorption, generates purely geometric entanglement between remote matters in a process that is insensitive of time, frequency, and space mode matching, which paves the way for building a noise-resilient quantum repeater network or a quantum internet.

Quantum Fourier transform is the building block for creating entanglement

This study demonstrates entanglement can be exclusively constituted by quantum Fourier transform (QFT) blocks. A bridge between entanglement and QFT will allow incorporating a spectral analysis to the already traditional temporal approach of entanglement, which will result in the development of new more performant, and fault-tolerant protocols to be used in quantum computing as well as quantum communication, with particular emphasis in the future quantum Internet.

Ultra-Compact and Ultra-Broadband Polarization-Insensitive Mach–Zehnder Interferometer in Silicon-on-Insulator Platform for Quantum Internet Application

Polarization dependence in integrated silicon photonics has a detrimental effect on the manipulation of quantum state with different polarizations in the quantum technology. Those limits have profound implications for further technological developments, especially in quantum photonic internet. Here, we propose a polarization-independent Mach–Zehnder interferometer (MZI) structure based on a 340 nm-thick silicon-on-insulator (SOI) platform. The MZI facilitates low loss, broad operating bandwidth, and large tolerance of the fabrication imperfection. We achieve an excess loss of <10% and an extinction radio of >18 in the 100 nm bandwidth (1500∼1600 nm) for both transverse electric (TE) and transverse magnetic (TM) modes. We numerically demonstrate an interference visibility of 99% and a polarization-independent loss (PDL) of 0.03 for both polarizations at 1550 nm. Furthermore, by using the principle of phase compensation and self-image, we shorten the length of the waveguide taper by almost an order of magnitude with the transmission of >95% for both TE and TM polarizations. Up to now, the proposed structure could significantly improve the integration and promote the development of monolithic integrated quantum internet.

Client-server Identification Protocols with Quantum PUF

Recently, major progress has been made towards the realisation of quantum internet to enable a broad range of classically intractable applications. These applications such as delegated quantum computation require running a secure identification protocol between a low-resource and a high-resource party to provide secure communication. In this work, we propose two identification protocols based on the emerging hardware-secure solutions, the quantum Physical Unclonable Functions (qPUFs). The first protocol allows a low-resource party to prove its identity to a high-resource party and in the second protocol, it is vice versa. Unlike existing identification protocols based on Quantum Read-out PUFs that rely on the security against a specific family of attacks, our protocols provide provable exponential security against any Quantum Polynomial-Time adversary with resource-efficient parties. We provide a comprehensive comparison between the two proposed protocols in terms of resources such as quantum memory and computing ability required in both parties as well as the communication overhead between them.