Phys.org June 17, 2020 A team of researchers in the US (University of Chicago, Argonne National Laboratory, UC Santa Barbara) developed a system that entangled two communication nodes using microwave photons through a microwave cable about a meter in length. By turning the system on and off in a controlled manner, they were able to quantum-entangle the two nodes and send information between them without ever having to send photons through the cable. In principle, this would also work over a much longer distance. Using a system built to communicate with phonons, they entangled two microwave phonons. They used one […]
Tag Archives: Communications technology
Light, sound, action: Extending the life of acoustic waves on microchips
EurekAlert May 6, 2020 An international team of researchers (Australia, Germany, Denmark) propose to use phonons to store and transfer information that chips receive from fibre-optic cables. They show a way to counteract the intrinsic acoustic decay of the phonons in a waveguide by resonantly reinforcing the acoustic wave via synchronized optical pulses. They experimentally demonstrated coherent on-chip storage in amplitude and phase up to 40 ns, 4 times the intrinsic acoustic lifetime in the waveguide. Through theoretical considerations, they anticipate that this concept allows for storage times up to microseconds within realistic experimental limitations while maintaining a GHz bandwidth […]
A breakthrough in estimating the size of a (mostly hidden) network
Phys.org April 22, 2020 For homogeneous networks accessing a mere 10% of the units could be sufficient to exactly infer the size of the entire network. But the same approach fails for heterogeneous networks, which are far more common in the field of complex systems. Researchers at New York University present a model-free approach to address this problem by studying the rank of a detection matrix that collates sampled time series of perceptible nodes from independent experiments. They unveil a connection between the rank of the detection matrix and the control-theoretic notion of observability. With this information it is to […]
A perovskite-based diode capable of both light emission and detection
Phys.org April 10, 2020 An international team of researchers (Sweden, China, Italy, Switzerland) has developed an efficient solution-processed perovskite diode that can work in both emission and detection modes. The device can be switched between modes by changing the bias direction, and it exhibits light emission with an external quantum efficiency of over 21% and a light detection limit on a subpicowatt scale. The operation speed for both functions can reach tens of megahertz. The diodes exhibit a high specific detectivity at its peak emission (~804 nm), which allows an optical signal exchange between two identical diodes. To illustrate the potential […]
Towards an unhackable quantum internet
Eurekalert March 23, 2020 To send quantum signals across large distances without loss a team of researchers in the US (Harvard University, MIT) found a way to correct for signal loss with a prototype quantum node that can catch, store and entangle bits of quantum information by integrating an individual color-center into a nanofabricated diamond cavity, which confines the information-bearing photons and forces them to interact with the single color-center. They placed the device in a dilution refrigerator, which reaches temperatures close to absolute zero, and sent individual photons through fiber optic cables into the refrigerator, where they were efficiently […]
Chip-based devices improve practicality of quantum-secured communication
Science Daily March 19, 2020 A team of researchers in the UK present secure key exchange up to 200 km while removing all side-channels from the measurement system. They used mass-manufacturable, monolithically integrated transmitters that represent an accessible, quantum-ready communication platform. This work demonstrates a network topology that allows secure equipment sharing which is accessible with a cost-effective transmitter, significantly reducing the barrier for widespread uptake of quantum-secured communication…read more. Open Access TECHNICAL ARTICLE
Quantum memories entangled over 50-kilometer cable
Phys.org February 13, 2020 Researchers in China have demonstrated entanglement of two atomic ensembles in one laboratory via photon transmission through city-scale optical fibres. The atomic ensembles function as quantum memories that store quantum states. They used cavity enhancement to efficiently create atom–photon entanglement and quantum frequency conversion to shift the atomic wavelength to telecommunications wavelengths. They realized entanglement over 22 kilometres of field-deployed fibres via two-photon interference and entanglement over 50 kilometres of coiled fibres via single-photon interference. The experiment could be extended to nodes physically separated by similar distances, which would thus form a functional segment of the […]
Extending Quantum Entanglement Across Town
IEEE Spectrum February 4, 2020 In an experiment researchers in Germany transferred the information contained in a single quantum bit from an atomic state to a single photon, then sent it through some 20 kilometers of fiber optic cable. They generated and observed the entanglement between a rubidium atom and a photon whose wavelength was transformed from 780 nm to the telecom S band at 1522 nm. The researchers found they can preserve on average some 78 percent of the entanglement between the rubidium atom and the fiber optic photon. Their next steps are to build out the full atom-to-photon-to-atom […]
A new twist on quantum communication in fiber
Phys.org January 24, 2020 While Hilbert spaces with higher dimensionality it requires custom multimode fiber and limited by decoherence-induced mode coupling. An international team of researchers (China, South Africa) circumvented this by transporting multidimensional entangled states down conventional single-mode fiber (SMF). By entangling the spin-orbit degrees of freedom of a biphoton pair, passing the polarization (spin) photon down the SMF while accessing multiple orbital angular momentum (orbital) subspaces with the other, they realized multidimensional entanglement transport. They demonstrated transfer of multi-dimensional entanglement states over 250 m of single-mode fiber, showing that an infinite number of two-dimensional subspaces could be realized. […]
Physicists find ways to overcome signal loss in magnonic circuits
Nanowerk January 2, 2020 Researchers in Russia analytically investigated properties of magnetostatic surface spin wave propagation in irregular narrow ferromagnetic waveguides that are important elements of magnonic logic. They demonstrated that the confinement effect in the narrow waveguide leads to multimode regime propagation, wave beats, and energy redistribution. These processes can be controlled by tuning the structure and excitation parameters. A gradual change in the waveguide width can be used to vary the spin wave energy density. Our results show that the impact of the width effect and the irregularity of the waveguide on the spin wave propagation are crucial. […]