New technology developed for quantum cryptography applications

Phys.org  May 10, 2023 Temporal modes (TMs), an encoding basis based on the time-frequency degree of freedom of photons, represent one of the most promising high-dimensional alphabets. TM-based quantum communication has until now been limited to a two-dimensional space due to the lack of a suitable decoder. However, quantum communication protocols based on single-photon TMs require suitable multichannel decoders. Researchers in Germany have demonstrated a new device that facilitates demultiplexing of high-dimensional TMs of single photons, and implemented a complete five-dimensional decoder that enables TM-based high-dimensional quantum key distribution. They showed that it is possible to scale the presented decoder […]

‘SuperGPS’ Technology Accurately Pinpoints Your Position Within Inches

Science Alert  November 23, 2022 Although GNSS can provide centimetre-level precision, GNSS receivers are prone to many-metre errors owing to multipath propagation and an obstructed view of the sky, which occur particularly in urban areas where accurate positioning is most needed. Moreover, the vulnerabilities of GNSS, combined with the lack of a back-up system, pose a severe risk to GNSS-dependent technologies. Researhers in the Netherlands have demonstrated a terrestrial positioning system that is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronized at the subnanosecond level through a fibre-optic Ethernet network. Using optical […]

A navigation system with 10 centimeter accuracy

Science Daily  November 16, 2022 The vulnerabilities of Global navigation satellite systems (GNSS) combined with the lack of a back-up system pose a severe risk to GNSS-dependent technologies. Researchers in the Netherlands used optical and wireless transmission schemes similar to those encountered in mobile communication networks, and exploiting spectrally efficient virtual wideband signals. The detrimental effects of multipath propagation were mitigated, thus enabling robust decimetre-level positioning and subnanosecond timing in a multipath-prone outdoor environment. They demonstrated that their system is independent of GNSS and offers superior performance through a constellation of radio transmitters, connected and time-synchronized at the subnanosecond level […]

The entanglement of two quantum memory systems 12.5 km apart from each other

Phys.org  August 16, 2022 Researchers in China have reported the establishment of post selected entanglement between two atomic quantum memories physically separated by 12.5 km. They created atom-photon entanglement in one node and sent the photon to a second node for storage via electromagnetically induced transparency. They harnessed low-loss transmission through a field-deployed fiber of 20.5 km by making use of frequency down-conversion and up-conversion. The final memory-memory entanglement was verified to have a fidelity of 90% via retrieving to photons. According to the researchers their experiment makes a significant step forward toward the realization of a practical metropolitan-scale quantum […]

An underwater navigation system powered by sound

MIT News  November 2, 2020 Researchers at MIT have designed and demonstrated the first underwater backscatter localization (UBL) system. The networks communicate by simply backscattering acoustic signals. While such backscatter-based communication enables them to operate at net-zero power, it also introduces new and unique challenges for underwater localization. They explored various challenges for bringing localization to underwater backscatter, including extreme multipath, acoustic delay spread, and mobility. In the article they describe how an adaptive and context-aware algorithm may address some of these challenges and adapt to diverse underwater environments (such as deep vs shallow water, and high vs low mobility). […]

Detection of very high frequency magnetic resonance could revolutionize electronics

Phys.org  January 27, 2020 A team of researchers in the US (UC Riverside, UC Santa Barbara) generated spin current in an antiferromagnet and were able to detect it electrically. They used terahertz radiation to pump up magnetic resonance in chromia to facilitate its detection. Although antiferromagnets are statically uninteresting, they are dynamically interesting. Electron spin precession in antiferromagnets is much faster than in ferromagnets, resulting in frequencies that are two-three orders of magnitude higher than the frequencies of ferromagnets—thus allowing faster information transmission…read more. TECHNICAL ARTICLE

A new alphabet to write and read quantum messages with very fast particles

Phys.org  September 2, 2019 If the quantum particle is relativistic it is impossible for standard techniques to decode the message unambiguously, and the communication therefore fails. Researchers in Austria deliver a new definition of the spin of quantum particles that move very quickly. It modifies both the way Anna writes the message and the way Bill reads it. Key to this technique is a “translation” of the way the message would be written and read between the standard alphabet used when the electron is at rest, and the new alphabet used when the electron travels very fast. These results indicate […]

Researchers turn off backscattering, aim to improve optical data transmission

Nanowerk  August 12, 2019 The most common manifestation of subwavelength disorder is Rayleigh light scattering, which is observed in nearly all waveguiding technologies today and can lead to both irreversible radiative losses as well as undesirable intermodal coupling. A team of researchers in the US (University of Illinois, University of Maryland, NIST) has demonstrated an optomechanical approach for dynamically suppressing Rayleigh backscattering within dielectric resonators by locally breaking the time-reversal symmetry in a silica resonator through a Brillouin scattering interaction that is available in all materials. They confirmed complete suppression of Rayleigh backscattering in their experiment through two independent measurements—the […]

Experimental brain-controlled hearing aid decodes, identifies who you want to hear

Science Daily  May 15, 2019 When two people talk to each other, the brain waves of the speaker begin to resemble the brain waves of the listener. Using this knowledge a team of researchers in the US (Columbia University, Hofstra-Northwell School of Medicine and Feinstein Institute for Medical Research) combined powerful speech-separation algorithms with neural networks, complex mathematical models that imitate the brain’s natural computational abilities to create a system that first separates out the voices of individual speakers from a group, and then compares the voices of each speaker to the brain waves of the person listening. The speaker […]

Virtually energy-free superfast computing invented by scientists using light pulses

Science Daily  May 15, 2019 An international team of researchers (Germany, USA- UC Santa Barbara, Russia, the Netherlands) utilized the efficient interaction mechanism of coupling between spins and terahertz electric field, which was discovered by the same team. They developed and fabricated a very small antenna on top of the magnet to concentrate and thereby enhance the electric field of light. This strongest local electric field was sufficient to navigate the magnetization of the magnet to its new orientation in just one trillionth of a second without increasing the temperature. Future storage devices would also exploit the excellent spatial definition […]