Phys.org June 19, 2019 An international team of researchers (Germany, Spain, Japan) conducted an experiment to develop a protocol for preparing a remote quantum state over a distance of 35 centimetres while conducting communication in the microwave regime. By employing propagating two-mode squeezed microwave states and feedforward, they achieved the remote preparation of squeezed states with up to 1.6 dB of squeezing below the vacuum level. They found nearly identical values for the entropy of the remotely prepared state and the respective conditional entropy given the classically communicated information and, thus, demonstrated close-to-perfect security…read more. Open Access TECHNICAL ARTICLE
Tag Archives: Communications technology
Multicolored light twists in new knotted ways
Phys.org June 10, 2019 An international team of researchers (Spain, Austria, USA- University of Colorado) has designed a beam of light with a polarization state that forms three-lobed trefoils at each point by combining light of different frequencies (w and 2w), and making the trefoils connect to each other in a way such that the light beam, as a whole, has the shape of a knot. They found new conservation laws for non-linear optics which hold even in extreme situations where tens or hundreds of photons get combined to form single high-frequency photons and a new optical singularity, robust against […]
Establishing the ultimate limits of quantum communication networks
Phys.org June 3, 2019 To fully understand the fundamental laws that prevent quantum communications to simultaneously achieve high rates and long distances, an international team of researchers (UK, USA – MIT) derived single-letter upper bounds for the end-to-end capacities achievable by the most general (adaptive) protocols of quantum and private communication, from a single repeater chain to an arbitrarily complex quantum network, where systems may be routed through single or multiple paths. They analytically established these capacities under fundamental noise models, including bosonic loss which is the most important for optical communications. The results provide the ultimate benchmarks for testing […]
Sculpting super-fast light pulses
Science Daily May 2, 2019 A team of researchers (NIST, University of Maryland) has demonstrated how dielectric metasurfaces can be leveraged to shape the temporal profile of a near-infrared femtosecond pulse. Finely tailored pulse shaping operations, including splitting, compression, chirping and higher-order distortion are achieved using a Fourier-transform setup embedding metasurfaces able to manipulate, simultaneously and independently, the amplitude and phase of the constituent frequency components of the pulse. Exploiting metasurfaces to manipulate the temporal characteristics of light expands their impact and opens new vistas in the field of ultrafast science and technology…read more. TECHNICAL ARTICLE
Researchers take a step towards light-based, brain-like computing chip
Nanowerk May 8, 2019 Unlike real neural tissue, traditional computing architectures physically separate the core computing functions of memory and processing, making fast, efficient and low-energy computing difficult to achieve. An international team of researchers (Germany, UK) present an all-optical version of a neurosynaptic system, capable of supervised and unsupervised learning. They exploit wavelength division multiplexing techniques to implement a scalable circuit architecture for photonic neural networks, successfully demonstrating pattern recognition directly in the optical domain. Such photonic neurosynaptic networks promise access to the high speed and high bandwidth inherent to optical systems, thus enabling the direct processing of optical […]
America may outsmart China in 5G with AI and blockchains
MIT Technology Review May 7, 2019 According to the FCC it will be imperative to devise better ways to allocate the spectrum. DARPA is organizing a competition to devise new ways of negotiating over spectrum using AI. Just as the wireless data available to smartphones has spurred technological progress, 5G should underpin innovation across the tech industry. AI and blockchains could be crucial to helping the US stay competitive with China in wireless technology…read more.
Researchers transmit data via a semiconductor laser, opening the door to ultra-high-speed Wi-Fi
Phys.org April 25, 2019 Previously the team of researchers in the US (Harvard University, Texas A&M, MIT Lincoln Laboratory) discovered that an infrared frequency comb in a quantum cascade laser could be used to generate terahertz frequencies, quantum cascade laser frequency combs could also act as integrated transmitters or receivers to efficiently encode information. Now they created a dipole antenna on the electrode of the device, modulated the frequency comb to encode information on the microwave radiation created by the beating light of the comb. Using the antenna, the microwaves containing the encoded information are radiated out from the device. […]
Researchers develop way to control speed of light, send it backward
Phys.org April 4, 2019 Controlling the group velocity of an optical pulse typically requires traversing a material or structure whose dispersion is judiciously crafted. Alternatively, the group velocity can be modified in free space by spatially structuring the beam profile. A team of researchers in the US (University of Central Florida, Purdue University) has demonstrated precise and versatile control over the group velocity of a propagation-invariant optical wave packet in free space through sculpting its spatio-temporal spectrum. By jointly modulating the spatial and temporal degrees of freedom, arbitrary group velocities are unambiguously observed in free space above or below the […]
Unlocking the untapped potential of light in optical communications
Phys.org March 8, 2019 The optical vortex carries the orbital angular momentum of light and can be used to multiplex signals by assigning each signal to a light wave of different momentum. Researchers in Japan designed and fabricated an orbital angular momentum multiplexing/demultiplexing module that could take five independent signals as input. Using a combination of two tiny circuit structures, called a star coupler and an optical-vortex generator, each of the five signals is “encoded” with a unique optical angular momentum. The output signal consists of a combination of the five signals, and the receiver circuit carries out the multiplexing […]
Overtones can provide faster data communication
Phys.org January 10, 2019 An international team of researchers (Sweden, Portugal) demonstrated how to play and strengthen overtones at the nano level. The researchers have produced spintronic oscillators that strengthen spin wave signals in several steps. When they increased the drive current, the signal showed a sharp jump in frequency: first, from the fundamental frequency of 9 GHz to 14 GHz and then a second jump to 20 GHz. While the wavelength of the fundamental tone is about 500 nanometres, the wavelength of the demonstrated third overtone is as short as 74 nanometres. Future studies on smaller oscillators should be […]