EurekAlert February 10, 2021 Both quantum computation and quantum communication are strongly deteriorated because quantum superposition state can be destroyed, or entanglement between two or more quantum particles can be lost. An international team of researchers (Austria, UK, Hong Kong, Switzerland, France, Canada) experimentally and numerically compare different ways in which two trajectories through a pair of noisy channels can be superposed. They observed that, within the framework of quantum interferometry, the use of channels in series with quantum-controlled operations generally yields the largest advantages. The results contribute to clarify the nature of these advantages in experimental quantum-optical scenarios and […]
Category Archives: Communications technology
Quantum tunneling in graphene advances the age of terahertz wireless communications
EurekAlert February 3, 2021 As the radiation frequency is raised to the sub-terahertz (THz) domain, ac-to-dc conversion by conventional electronics becomes challenging and requires alternative rectification protocols. An international team of researchers (Russia, UK) address this challenge by tunnel field-effect transistors made of bilayer graphene (BLG). Taking advantage of BLG’s electrically tunable band structure, they created a lateral tunnel junction and couple it to an antenna exposed to THz radiation. The incoming radiation was then down-converted by the tunnel junction nonlinearity, resulting in high responsivity and low-noise detection. They demonstrated how switching from intraband Ohmic to interband tunneling regime can […]
Terahertz accelerates beyond 5G towards 6G
TechXplore February 1, 2021 Researchers in Japan configured a two-channel terahertz transmitter (Tx) by modulating the output of a laser pair with wavelengths in the 1.55-micron band, which was set so that the frequency difference was in the 300-GHz band, with an 8K video signal source using an intensity modulator and converting it into terahertz waves using an ultrafast photodiode. After the wirelessly transmitted terahertz waves were detected by sensitive terahertz coherent receivers (Rxs) using resonant tunnel diodes (RTDs) they were split from the two channels into four channels and connected to an 8K monitor via HDMI cable. Using this […]
Long-distance and secure quantum key distribution (QKD) over a free-space channel
Phys.org January 25, 2021 Measurement-device-independent quantum key distribution (MDI-QKD) protocol can help in closing all loopholes on detection at once. It has only been successfully implemented using fiber optics. To implement the protocol across free-space channels two main challenges need to be addressed. One is to reduce the gap between theory and practice of QKD, and the other one is to extend the distance of QKD. Researchers in China have developed a robust adaptive optics system – high-precision time synchronization and frequency locking between independent photon sources located far apart to realize free-space MDI-QKD over a 19.2-km urban atmospheric channel. […]
Record-breaking laser link could help us test whether Einstein was right
Science Daily January 22, 2021 An international team of researchers (Australia, France) combined phase stabilisation technology with advanced self-guiding optical terminals that allowed laser signals to be sent from one point to another without interference from the atmosphere. They demonstrated phase-stabilized optical frequency transfer over a 265 m horizontal point-to-point free-space link between optical terminals with active tip-tilt mirrors to suppress beam wander, in a compact, human-portable set-up. They could correct for atmospheric turbulence in 3D, that is, left-right, up-down and, critically, along the line of flight. According to the researchers if you have one of these optical terminals on the […]
Using graphene, researchers increase optical data transmission speed by a factor of at least 10,000.
Nanowerk January 19, 2021 Conventional optical-fiber-based pulsed lasers have limits to increasing the number of pulses per second above the MHz level. Researchers in South Korea inserted an additional resonator containing graphene into a fiber-optic pulsed-laser oscillator that operates in the domain of femtoseconds (10-15 seconds). This increased data transmission and processing speeds significantly. They synthesized graphene, which has the characteristics of absorbing and eliminating weak light and amplifying the intensity by passing only strong light into the resonator. This allows the laser intensity change to be accurately controlled at a high rate, and thus the repetition rate of pulses […]
Perfect transmission through barrier using sound
Science Daily December 23, 2020 Tunneling plays an essential role in many branches of physics and has found important applications. It is theoretically proposed that Klein tunneling occurs when, under normal incidence, quasiparticles exhibit unimpeded penetration through potential barriers independent of their height and width. A team of researchers in the US (UC Berkeley, Georgia Institute of Technology, Lawrence Berkeley National Laboratory) created a phononic heterojunction by sandwiching two types of artificial phononic crystals with different Dirac point energies. They demonstrated direct observation of Klein tunneling as shown by the key feature of unity transmission. Their experiment reveals that Klein […]
World’s First Successful Transmission of 1 Petabit per Second Using a Single-core Multimode Optical Fiber
NICT Japan December 18, 2020 Researchers in Japan have demonstrated the possibility of combining highly spectral efficient wideband optical transmission with an optical fiber guiding 15 fiber modes that had a cladding diameter in agreement with the current industry standard of 0.125 mm. This was enabled by mode multiplexers and an optical fiber that supported wideband transmission of more than 80 nm over 23 km. The study highlights the large potential of single-core multi-mode fibers for high-capacity transmission using fiber manufacturing processes like those used in the production of standard multi-mode fibers. The results of this study were accepted for […]
Ultrathin spray-applied MXene antennas are ready for 5G
Science Daily November 30, 2020 Only conventional metals meet the requirements for emerging RF devices so far. A team of researchers in the US (Drexel University, Villanova University, industry) has developed Ti3C2Tx MXene microstrip transmission lines with low‐energy attenuation and patch antennas with high‐power radiation at frequencies from 5.6 to 16.4 GHz. The antenna was manufactured by spray‐coating from aqueous solution. They demonstrated that an MXene patch antenna array with integrated feeding circuits on a conformal surface has comparable performance with that of a copper antenna array at 28 GHz, which is a target frequency in practical 5G applications. The […]
New fiber optic sensors transmit data up to 100 times faster
EurekAlert November 16, 2020 Distributed optical fibre sensors deliver a map of a physical quantity along an optical fibre, providing a unique solution for health monitoring of targeted structures. An international team of researchers (China, Switzerland, Chile) propose a technique encoding the interrogating light signal by a single-sequence aperiodic code and spatially resolving the fibre information through a fast-post-processing. The code sequence is once forever computed by a specifically developed genetic algorithm, enabling a performance enhancement using an unmodified conventional configuration for the sensor. They demonstrated in Brillouin and Raman based sensors, both outperforming the state-of-the-art sensors. The new technique […]