Science Daily January 29, 2020 An international team of researchers (USA – NIST, University of Maryland, Japan, Canada) created weakly coupled quantum dots by using the ultrasharp tip of a scanning tunneling microscope as a stylus hovering the tip above an ultracold sheet of graphene briefly increasing the voltage of the tip penetrating through the graphene into an underlying layer of boron nitride. It stripped electrons from atomic impurities in the layer and created electric charge which corralled freely floating electrons in the graphene, confining them to a tiny energy well. When a magnetic field of 4 to 8 tesla […]
Category Archives: Quantum communication
In surprise breakthrough, scientists create quantum states in everyday electronics
Phys.org December 9, 2019 An international team of researchers (USA – University of Chicago, Argonne National Laboratory, Chicago, Japan, Sweden, Hungary) has demonstrated they could electrically control quantum states embedded in silicon carbide. The quantum states in silicon carbide have the added benefit of emitting single particles of light with a wavelength near the telecommunications band which makes them well suited to long-distance transmission through the same fiber-optic network. They found that by using the diode, a one-way switch for electrons the quantum signal suddenly became free of noise and was almost perfectly stable mitigating the impurity issue. The work […]
A new alphabet to write and read quantum messages with very fast particles
Phys.org September 2, 2019 If the quantum particle is relativistic it is impossible for standard techniques to decode the message unambiguously, and the communication therefore fails. Researchers in Austria deliver a new definition of the spin of quantum particles that move very quickly. It modifies both the way Anna writes the message and the way Bill reads it. Key to this technique is a “translation” of the way the message would be written and read between the standard alphabet used when the electron is at rest, and the new alphabet used when the electron travels very fast. These results indicate […]
Practical anonymous communication protocol developed for quantum networks
Phys.org August 21, 2019 In the protocol developed by an international team of researchers (UK, USA – MIT, France) the player who wants to send a message anonymously notifies the receiver. Then, in each round of the protocol, an untrusted source creates an entangled quantum state called the Greenberger-Horne-Zeilinger (GHZ) state and distributes it between the players. Each player can either check if the state is actually the GHZ state by running a verification test or use the state for anonymous quantum communication. If test fails, there is possible breach, the misbehaving source is caught. If they use the state […]
Travelling towards a quantum internet at light speed
Science Daily July 29, 2019 An international team of researchers (Japan, Germany) used laser light to send quantum information to a quantum dot by altering the spin state of a single electron trapped there. While electrons don’t spin in the usual sense, they do have angular momentum, which can be flipped when absorbing circularly polarized laser light. They were able to monitor the inter-dot charge tunneling which only occur when the photo-electron spin in one QD is anti-parallel to the electron spin in the other. The transfer of superposition states or entangled states allows for completely secure quantum key distribution […]
Secure quantum communications in the microwave range for the first time
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
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 […]
New robust device may scale up quantum tech, researchers say
Phys.org April 24, 2019 A theory developed only two years ago proposed a way to make qubits more resilient through combining a semiconductor, indium arsenide, with a superconductor, aluminum, into a planar device. An international team of researchers (Denmark, USA – University of Chicago, Purdue University, Israel) has provided experimental support to the theory in a device that could also aid the scaling of qubits. These experiments provide evidence that aluminum and indium arsenide, when brought together to form a device called a Josephson junction, can support Majorana zero modes, which scientists have predicted possess topological protection against decoherence. The […]
Long-distance quantum information exchange—success at the nanoscale
Phys.org March 15, 2019 An international team of researchers (Denmark, Australia, USA – Purdue University) discovered that by placing a large, elongated quantum dot between the left dots and right dots, it can mediate a coherent swap of spin states, within a billionth of a second, without ever moving electrons out of their dots. In other words, we now have both fast interaction and the necessary space for the pulsed gate electrodes. The research may have profound implications for the architecture of solid-state quantum computers allowing the realization of networks in which the increased qubit-qubit connectivity translated into a significantly […]
Global Quantum Communication Network has Been Proven Feasible With 20,000 km Transmissions
Next Big Future December 24, 2018 Researchers in Italy have reported on the first experimental exchange of single photons from Global Navigation Satellite System at a slant distance of 20000 kilometers, by exploiting the retroreflector array mounted on GLONASS satellites. They observed the predicted temporal spread of the reflected pulses due to the geometrical shape of array. They provide estimated the requirements needed for an active source on a satellite, aiming towards quantum communication from GNSS with state-of-the-art technology… read more. Open Access TECHNICAL ARTICLE