Phys.org March 9, 2021 With the growing availability of experimental loophole-free Bell tests it has become possible to implement a new class of device-independent random number generators whose output can be certified to be uniformly random without requiring a detailed model of the quantum devices used. However, all these experiments require many input bits to certify a small number of output bits, and it is an outstanding challenge to develop a system that generates more randomness than is consumes. An international team of researchers (USA -University of Colorado, NIST, University of Maryland, Spain, Japan) developed a device-independent spot-checking protocol that […]
Tag Archives: Communications technology
Light unbound: Data limits could vanish with new optical antennas
UC Berkeley February 25, 2021 The quantum Hall effect involves electrons confined to a two-dimensional plane subject to a perpendicular magnetic field, but it also has a photonic analogue. Using heterostructures based on structured semiconductors on a magnetic substrate, a team of researchers in the US (UC San Diego, UC Berkeley) introduced compact and integrated coherent light sources of large orbital angular momenta based on the photonic quantum Hall effect. The photonic quantum Hall effect enables the direct and integrated generation of coherent orbital angular momenta beams of large quantum numbers from light travelling in leaky circular orbits at the […]
Light used to detect quantum information stored in 100,000 nuclear quantum bits
Phys.org February 15, 2021 An international team of researchers (UK, France) injected a ‘needle’ of highly fragile quantum information in a ‘haystack’ of 100,000 nuclei. By using lasers to control an electron, they could use that electron to control the behavior of the haystack, making it easier to find the needle. By controlling the collective state of the 100,000 nuclei, they were able to detect the existence of the quantum information as a ‘flipped quantum bit’ at an ultra-high precision of 1.9 parts per million: enough to see a single bit flip in the cloud of nuclei. Using this technique, […]
Quantum systems learn joint computing
Phy.org February 5, 2021 The big challenge in quantum computing is to realize scalable multi-qubit systems with cross-talk–free addressability and efficient coupling of arbitrarily selected qubits. Quantum networks promise a solution by integrating smaller qubit modules to a larger computing cluster. Such a distributed architecture, however, requires the capability to execute quantum-logic gates between distant qubits. An international team of researchers (Germany, Spain) experimentally realized such a gate over 60 meters. They employed an ancillary photon that they successively reflected from two remote qubit modules, followed by a heralding photon detection, which triggers a final qubit rotation. They used the […]
A trillion turns of light nets terahertz polarized bytes
Phys.org October 19, 2020 Ultrafast nanophotonics is an emerging research field aimed at the development of nanodevices capable of light modulation with unprecedented speed. An international team of researchers (Italy, USA – Rice University) demonstrated that the inhomogeneous spacetime distribution of photogenerated hot carriers induces a transient symmetry breaking in a highly symmetric plasmonic metasurface. The process is fully reversible and results in a broadband transient dichroism with a recovery of the initial isotropic state in less than 1 ps, overcoming the speed bottleneck caused by slower (electron–phonon and phonon–phonon) relaxation processes. Their results pave the way to ultrafast dichroic devices […]
Demonstrating entanglement through a fiber cable with high fidelity
Phys.org August 13, 2020 Researchers in the UK exploited a property of quantum physics that allows for mapping the medium (fiber cable) onto the quantum state of a particle moving through it to transport entangled particles through a commercial fiber cable with 84.4% fidelity. They sent one of a pair of photons through a complex medium, but not the other. Both were then directed toward spatial light modulators and then on to detectors, and then finally to a device used to correlate coincidence counting. In their setup, light from the photon that did not pass through the complex medium propagated […]
An electrical switch for magnetism
Phys.org August 6, 2020 Electrical control of magnetism in van der Waals ferromagnetic semiconductors is an important step in creating novel spintronic devices capable of processing and storing information. Using an electric double-layer transistor device, an international team of researchers (Singapore, UK, China) discovered that the magnetism of a magnetic semiconductor, Cr2Ge2Te6, shows exceptionally strong response to applied electric fields. With electric fields applied, the material was found to exhibit ferromagnetism at temperatures up to 200 K (-73°C). At such temperatures, ferromagnetic order is normally absent in this material. Their analysis suggests that heavy doping promotes a double-exchange mechanism that […]
A completely new plasmonic chip for ultrafast data transmission using light
Techxplore.com July 3, 2020 To address the challenge of increasing data rates an international team of researchers (Switzerland, Germany, USA- University of Washington, Israel, Greece) has developed a monolithically integrated electro-optical transmitter that can achieve symbol rates beyond 100 GBd. They combined advanced bipolar CMOS with silicon plasmonics, and addressed key challenges in monolithic integration through co-design of the electronic and plasmonic layers, including thermal design, packaging, and a nonlinear organic electro-optic material. They demonstrated their technique by developing two modulator concepts—an ultra-compact plasmonic modulator and a silicon-plasmonic modulator with photonic routing—both directly processed onto the bipolar CMOS electronics. The findings […]
Scientists Have Demonstrated Quantum Entanglement on a Tiny Satellite Orbiting Earth
Science Alert June 28, 2020 A CubeSat launched last year from the International Space Station was specially designed to shield the entangled photon source from the pressures and temperatures of a launch from Earth. An international team of researchers (Singapore, Turkey, Switzerland, Australia, UK) describes the experiment which is composed of a source of entangled photon pairs coupled to a detector module all controlled by an integrated electronics subsystem. A micro-controller on the experiment interfaces to the satellite’s on-board computer to receive commands and to return science data to ground control. It operates using as little power as possible. The […]
Adding noise for completely secure communication
Science Daily June 11, 2020 Device-independent quantum key distribution provides security even when the equipment used to communicate over the quantum channel is largely uncharacterized. A central obstacle in photonic implementations is that the global detection efficiency, i.e., the probability that the signals sent over the quantum channel are successfully received, must be above a certain threshold. Researchers in Switzerland developed a protocol that adds artificial noise, which cannot be known or controlled by an adversary, to the initial measurement data (the raw key). Focusing on a realistic photonic setup using a source based on spontaneous parametric down conversion, they […]