Arxiv July 11. 2018 An international team of researchers (Russia, Poland) has demonstrated niobium nitride based superconducting single-photon detectors are sensitive in the spectral range 457 nm – 2300 nm. The system performance was tested in a real-life experiment with correlated photons generated by means of spontaneous parametric down conversion, where one of photon was in the visible range and the other was in the infrared range. They measured a signal to noise ratio as high as 4×104 in their detection setting. A photon detection efficiency as high as 64 % at 1550 nm and 15 % at 2300 nm […]
Tag Archives: Communications technology
New study could hold key to hack-proof systems
Phys.org July 17, 2018 An international team of researchers (Austria, France, Czech Republic, Slovakia, Switzerland, Spain, UK) show how carefully constructed measurements in two bases (one of which is not orthonormal) can be used to faithfully and efficiently certify bipartite high-dimensional states and their entanglement for any physical platform. In an experimental set-up, they were able to verify 9-dimensional entanglement for a pair of photons on a 11-dimensional subspace each. The group is currently looking into a more direct use of this technique in actual quantum cryptography protocols and expect their technique to be widely applied in other quantum systems […]
A Step Toward Quantum Repeaters
Optics and Photonics July 6, 2018 An international team of researchers (USA – Princeton University, Gemological Institute of America, UK) reports a color center that shows insensitivity to environmental decoherence caused by phonons and electric field noise: the neutral charge state of silicon vacancy (SiV0). Through careful materials engineering, they achieved >80% conversion of implanted silicon to SiV0. SiV0 exhibits spin-lattice relaxation times approaching 1 minute and coherence times approaching 1 second. Its optical properties are very favorable, with ~90% of its emission into the zero-phonon line and near–transform-limited optical linewidths. These combined properties make SiV0 a promising defect for […]
Physicists show that is impossible to mask quantum information in correlations
Phys.org June 21 2018 Classical information encoded in composite quantum states can be completely hidden from the reduced subsystems and may be found only in the correlations. An international team of researchers (Australia, India) has shown that while this may still be true for some restricted sets of nonorthogonal quantum states, it is not possible for arbitrary quantum states. This result suggests that quantum qubit commitment—a stronger version of the quantum bit commitment—is not possible in general. The findings may have potential applications in secret sharing and future quantum communication protocols…read more. TECHNICAL ARTICLE
New laser makes silicon ‘sing’
Eurekalert June 7, 2018 To amplify silicon laser with sound, a team of researchers in the US (Yale University, Northern Arizona University, UT Austin) used a nanoscale waveguide that is designed to tightly confine both light and sound waves and maximize their interaction. The waveguide has two distinct channels for light to propagate which allows shaping of the light-sound coupling in a way that permits remarkably robust and flexible laser designs. While the system is clearly an optical laser, it also generates very coherent hypersonic waves. According to the researchers these properties may lead to several potential applications ranging from […]
A microscopic roundabout for light—team develops a magnet-free optical circulator
Phys.org May 4, 2018 To break the symmetry of light propagation, instead of magnet, an international team of researchers (The Netherlands, USA – UT Austin, City University of New York, City College of New York) created circulating behavior using a microscale glass ring resonator by letting light in the ring interact with the ring’s mechanical vibrations. Careful control of the optical paths in the structure ensures that light from each input constructively interferes in exactly the right output. They demonstrated that circulation can be actively tuned and it can be turned on and off by controlling the frequency and power […]
3D Nanoprinting facilitates communication with light
Nanowerk April 20, 2018 Researchers in Germany have developed a new solution for the coupling of optical microchips to each other or to optical fibers. They use tiny beam-shaping elements that are printed directly onto the facets of optical components by a high-precision 3D printing process. These elements can be produced with nearly any three-dimensional shape and enable low-loss coupling of various optical components with a high positioning tolerance. They produced beam-shaping elements of various designs and tested them on a variety of chip and fiber facets and reached coupling efficiencies of up to 88% between an indium phosphide laser […]
Tuning in to magnetic ink
Eurekalert April 4, 2018 By injecting iron-based reagents into a hot acetic acid solution, researchers in Saudi Arabia synthesized magnetic iron-oxide nanoparticles that dispersed into deionized water to form an ink. When deposited as a thin film on a glass substrate, the new magnetic substrate could act as an energy-storing inductor device with an adjustable capacity of over 20 percent. By modifying the nanoparticles’ surfaces with hydrocarbon chains, they were able to produce free-standing magnetic sheets of a few millimeters in thickness. The discovery boosts prospects for inexpensive electronics that work worldwide by tuning in to multiple cellular bands and […]
Scientists gain new visibility into quantum information transfer
MIT News March 8, 2018 A team of researchers in the US (MIT, Dartmouth College) combined NMR techniques with their knowledge of the spin dynamics in their crystal, whose geometry approximately confines the evolution to linear spin chains. It allowed them to figure out a metric, average correlation length, for how many spins are connected to each other in a chain and determine if the interaction is winning or disorder is winning keeping the system in a more quantum localized state. The method represents a possible advance toward the ability to control localization. Because many-body localization preserves information and prevents […]
‘Two-way signaling’ possible with a single quantum particle
Physorg February 26, 2018 By using a quantum particle that has been put in a superposition of two different locations, researchers in Austria have theoretically shown that both partners are able to encode their messages into a single quantum particle simultaneously. Being in a quantum superposition means that the quantum particle is “simultaneously present” at each partner’s location. Therefore, both partners are able to encode their messages into a single quantum particle simultaneously, a task that is essentially impossible using classical physics. The experimental results show that the communication is secure and anonymous, the direction of communication is hidden—an eavesdropper […]