Phys.org May 10, 2021 One solution for remote quantum communication lies in quantum memories: photons are stored in long-lived quantum memory (quantum flash drive) and then quantum information is transmitted by the transportation of the quantum memory. Researchers in China adopted the spin wave atomic frequency comb (AFC) protocol in a ZEFOZ field (ZEFOZ-AFC) method to implement long-lived storage of light signals. They used dynamical decoupling to protect spin coherence and extend storage time. They demonstrated coherent storage of light in an atomic frequency comb memory over 1 hour with a fidelity of 96.4%. The study meets the basic requirements […]
Category Archives: Communications technology
Flexible, easy-to-scale nanoribbons move graphene toward use in tech applications
Science Daily May 3, 2021 Silicon-based fiber optics are currently the best structures for high-speed, long distance transmissions, but graphene could improve performance even more. Researchers at the University of Wisconsin created a scalable fabrication technique to make the smallest graphene ribbon structures. They found that to improve graphene’s performance is to cut it into microscopic, nanometer-scale ribbon structures, which act as tiny antennas that interact with light. The smaller the antenna, the higher energies of light it interacts with. As the ribbon width decreases, so does the resonant wavelength of light. Lower wavelengths mean higher energies, and their devices interacted […]
Researchers complete high-precision time-frequency dissemination
Phys.org April 26, 2021 Microwave-based satellite–ground links cannot fully satisfy the requirements of metrology, navigation, positioning, and very long baseline interferometers. Researchers in China investigated the possibility of an optical-based satellite–ground link, where the transferred carriers are pulsed lasers, resulting in a link with a high time resolution and a large ambiguous range. They analyzed the parameters of satellites in different orbits and concluded that high-orbit links enable more stable time–frequency comparison or dissemination by taking advantage of the long duration, a large common view range, and the lower relativistic effects. They performed a 16 km free-space transfer experiment to […]
Counting single photons at unprecedented rates
Phys.org April 13, 2021 Researchers at NIST have demonstrated a method that allows a high-efficiency single-photon-avalanche diode (SPAD) with a thick absorption region to count single photons at rates significantly higher than previously demonstrated. They applied large (>30 V) AC bias gates to the SPAD at 1 GHz and detected minute avalanches by means of radio frequency interferometry. They measured a reduction by a factor of ≈500 in the average charge per avalanche when compared to operation in its traditional active-quenching module and a relative increase in >19% in detection efficiency at 850 nm. The reduction in charge strongly suppresses self-heating effects in the […]
Atom-based radio communications for noisy environments
Science Daily April 5, 2021 Previously NIST researchers had demonstrated that atom-based sensors can receive commonly used communications signals. Now a team of researchers in the US (University of Colorado, NIST) used a Rydberg atom-based sensor for determining the angle of arrival of an incident RF signal, key part for a potential atomic communications system. They measured phase differences of a 19.18 gigahertz experimental signal at two locations inside the vapor cell for various angles of arrival. Comparisons of these measurements with both the full-wave simulation and the plane wave theoretical model show that the atom-based sub-wavelength phase measurements can […]
A quantum internet is closer to reality, thanks to this switch
Phys.org March 2, 2021 In the emerging field of quantum networking, the need for effective resource provisioning is particularly acute, given the generally lower power levels, higher sensitivity to loss, and inapplicability of optical detection and retransmission. A team of researchers in the US (Purdue University, Oak Ridge National Laboratory) has demonstrated reconfigurable distribution of quantum entanglement in a four-user tabletop network. By adaptively partitioning bandwidth with a single wavelength-selective switch, they successfully equalized two-party coincidence rates that initially differed by over two orders of magnitude. Their scalable approach introduces loss that is fixed with the number of users, offering […]
International study reveals exceptional property of next generation optical fibers
EurekAlert February 15, 2021 The elastic backscattering of light in optical fiber is a fundamental phenomenon that sets the ultimate performance of several fiber systems such as gyroscopes and bidirectional transfer links. Until now, efforts to reduce the backscattering coefficient have yielded limited results. An international team of researchers (Canada, UK) measured backscattering from a low-loss antiresonant hollow-core fiber and showed that it is more than 40 dB below reported values in silica-core fiber and hollow-core photonic bandgap fiber. The record-low level of −118dB/m measured with their optical frequency-domain reflectometer is in good agreement with simulations in which they assumed […]
A performance leap for graphene modulators in next generation datacom and telecom
Nanowerk February 16, 2021 Electro-absorption (EA) waveguide-coupled modulators are essential building blocks for on-chip optical communications. Compared to state-of-the-art silicon devices, graphene-based EA modulators promise smaller footprints, larger temperature stability, cost-effective integration, and high speeds. However, combining high speed and large modulation efficiencies in a single graphene-based device has remained elusive so far. An international team of researchers (Spain, Italy, Belgium) overcame this fundamental trade-off by demonstrating the 2D-3D dielectric integration in a high-quality encapsulated graphene device. They integrated hafnium oxide and two-dimensional hexagonal boron nitride within the insulating section of a double-layer graphene EA modulator. This combination of materials […]
Wafer-scale production of graphene-based photonic devices
Science Daily February 11, 2021 Graphene has been recently proposed to be integrated with silicon photonics to meet the challenges of next generation optical communication to increase the available bandwidth while reducing the size, cost, and power consumption of photonic integrated circuits. An international team of researchers (Italy, UK) focused on graphene photodetectors for high speed datacom and telecom applications based on the photo-thermo-electric effect, allowing for direct optical power to voltage conversion, zero dark current, and ultra-fast operation. They reported on a chemical vapour deposition graphene photodetector based on the photo-thermoelectric effect, integrated on a silicon waveguide, providing frequency […]
Capturing Free-Space Optical Light for High-Speed WiFi
Duke University February 9, 2021 Visible and infrared light can carry more data than radio waves, but has always been confined to a hard-wired, fiber-optic cable. A team of researchers in the US (Duke University, industry) has demonstrated a low-loss plasmonic metasurface that can collect fast-modulated light with a 3 dB bandwidth exceeding 14 GHz and a 120º acceptance angle and convert it to a directional source with an overall efficiency of ∼30%. This exhibits a 910-fold increase in the overall fluorescence and a 133-fold emission rate enhancement. The metasurface was created over macroscopic areas with scalable techniques and the […]