Phys.org July 14, 2022 An international team of researchers (Austria, France) has developed a method that allows the calculation of a tailor-made anti-reflective structure which can be used to design an additional layer to the medium only partially permeable to a wireless signal so that the entire signal can be channeled through the medium without reflections. To determine the anti-reflective structure they sent the waves through the medium and measured exactly in which way these waves are reflected by the material. Using a mathematical technique they calculated the corresponding compensating structure so that the combination of both media allowed the […]
Tag Archives: Communications technology
Researchers achieve record entanglement of quantum memories
Phys.org July 7, 2022 To fully use entanglement over long-distance quantum network links it is mandatory to know it is available at the nodes before the entangled state decays. An international team of researchers (Austria, Germany) demonstrated entanglement between two independently trapped single rubidium atoms generated over fibre links with a length up to 33 km. They generated atom–photon entanglement in two nodes located in buildings 400 m line-of-sight apart and to overcome high-attenuation losses in the fibres converted the photons to telecom wavelength using polarization-preserving quantum frequency conversion. The long fibres guided the photons to a Bell-state measurement setup in which […]
Chip-scale Floquet topological insulators to enhance 5G wireless communications
Phys.org May 30, 2022 A team of researchers in the US (Columbia University, City University of New York, UT Austin, industry) introduced Floquet topological insulators for radio-waves with a unique design, based on the quasi-electrostatic propagation of radio signals in switched-capacitor networks. In their previous work they developed photonic topological insulators (PTI) chips that could be used to create full-duplex phased-array wireless technology, which combines two different 5G wireless capabilities: full-duplex and multi-antenna operation. PTIs do not allow the propagation of electromagnetic waves in their bulk, but they ensure efficient and robust wave propagation on their boundaries, however shaped. These […]
Eavesdroppers can hack 6G frequency with DIY metasurface
Science Daily May 16, 2022 Metasurfaces enable controllable manipulation of electromagnetic waves and have been shown to improve wireless communications in many diverse ways. A team of researchers in the US (Rice University, Brown University) defined and experimentally demonstrated a “MetaSurface-in-the-Middle” (MSITM) attack. In this attack, the adversary Eve placed a metasurface in the path of a directive transmission between Alice and Bob and targeted to re-direct a portion of the signal towards herself, without being detected. They showed how to design a metasurface that induces abrupt phase changes at the interface of the metasurface to controllably diffract directional links […]
DARPA Seeks Ionospheric Insights to Improve Communication Across Domains
DARPA April 22, 2022 DARPA’s new Ouija program aims to use sensors on low-orbiting satellites to provide new insights into HF radio wave propagation in the ionosphere. Ouija will augment ground-based measurements with in-situ measurements from space, in very low- Earth orbit (VLEO), to develop and validate accurate, near real-time HF propagation predictions. The VLEO altitude regime is of particular interest due to its information-rich environment where ionospheric electron density is at a maximum. The program includes two technical areas. The first technical area announced in a solicitation, seeks to develop, qualify, launch, and operate multiple small satellites carrying scientific […]
Unexpected light behavior may be harnessed to improve optical communications and sensors
Phys.org April 21, 2022 Waves entering a spatially uniform lossy medium typically undergo exponential intensity decay, arising from either the energy loss or the evanescent penetration during reflection. A team of researchers in the US (NIST, University of Maryland, Texas Tech University, Carnegie Mellon University) proposed and demonstrated exponential decay free wave propagation in a purely lossy medium. They observed up to 400-wave deep polynomial wave propagation accompanied by a uniformly distributed energy loss across a nanostructured photonic slab waveguide with exceptional points. Using coupled-mode theory and fully vectorial electromagnetic simulations they predicted deep wave penetration manifesting spatially constant radiation […]
Chinese team breaks distance record for quantum secure direct communication
Phys.org April 20, 2022 Researchers in China have designed an elaborate physical system and protocol with much enhanced performance for quantum secure communication. The design increased the secrecy capacity greatly by achieving an ultra-low quantum bit error rate of <0.1%, one order of magnitude smaller than that of existing systems. Compared to previous systems, the proposed scheme used photonic time-bin and phase states, operating at 50 MHz of repetition rate, which can be easily upgraded to over 1 GHz using current on-the-shelf technology. Their experiments demonstrated that the proposed system could tolerate more channel loss, from 5.1 dB, which is about 28.3 km in […]
Quantum teleportation: The express lane for quantum data traffic
Phys.org April 11, 2022 Short-distance quantum encryption is already used commercially. However, to implement a global quantum network, photon loss becomes in issue. An international team of researchers (Australia, USA – NIST) demonstrated an error reduction method that improved the performance of a channel. They sent a photon which is not carrying any useful information, through the loss. Using a noiseless linear amplifier, they corrected for the effects of loss and recovered the lost quantum state to teleport the information they wanted to transmit into the now corrected carrier, avoiding all the loss on the channel. The arbitrary quantum information […]
New quantum dots for quantum networks
Phys.org April 7, 2022 Spin can be also used as the medium for quantum communication by transferring quantum information with light. But the process of transferring information to the spin of extremely small electrons is challenging and must be performed efficiently. An international team of researchers (Japan, Canada, Germany) has realized the world’s first GaAs gate-controlled quantum dot circuit on a (110)-oriented surface that promises to increase photon-electron spin conversion efficiency. This has the effect of encoding quantum information from incident photons into the electron spins. Because of the way the hole interacts with the GaAs crystal lattice, the g-factor, […]
Qubits: Developing long-distance quantum telecommunications networks
Science Daily March 22, 2022 An international team of researchers (Switzerland, France) has stored a qubit for 20 milliseconds in crystals doped with europium capable of absorbing light and then re-emitting it. They managed to reach the 100-millisecond mark with a small loss of fidelity. The crystals were kept at -273,15°C, because beyond 10°C above this temperature, the thermal agitation of the crystal destroys the entanglement of the atoms. In theory, it would be enough to increase the duration of exposure of the crystal to radio frequencies, but for the time being, technical obstacles to their implementation over a longer […]