Phys.org December 29, 2020 An international team of researchers (USA – Caltech, Fermi National Accelerator Laboratory, industry, Harvard University, Canada) used fiber-coupled devices, including state-of-the-art low-noise superconducting nanowire single-photon detectors and off-the-shelf optics to achieve conditional quantum teleportation of time-bin qubits at the telecommunication wavelength of 1536.5 nm. They measured teleportation fidelities that are consistent with an analytical model of their system, which includes realistic imperfections. To demonstrate the compatibility of the setup with deployed quantum networks, they teleported qubits over 22 km of single-mode fiber while transmitting qubits over an additional 22 km of fiber. Their systems, which are […]
Tag Archives: Quantum communication
Physicists develop efficient modem for a future quantum internet
Phys.org November 5, 2020 A central research object is the interface between local quantum devices and light quanta that enable the remote transmission of highly sensitive quantum information. Researchers in Germany integrated a thin crystal of erbium-doped yttrium orthosilicate a cryogenic Fabry-Perot resonator leading to 56-fold enhancement of the emission rate with an out-coupling efficiency of 46%. They demonstrated that the emitter properties are not degraded. They observed ensemble-averaged optical coherence up to 0.54 ms, which exceeds the 0.19 ms lifetime of dopants at the cavity field maximum. The approach is also applicable to other solid-state quantum emitters, such as […]
Generating photons for communication in a quantum computing system
Phys.org October 10, 2020 Realizing a fully connected network of quantum processors requires the ability to distribute quantum entanglement. For distant processing nodes, this can be achieved by generating, routing, and capturing spatially entangled itinerant photons. Researchers at MIT and MIT Lincoln Laboratory have demonstrated the deterministic generation of such photons using superconducting transmon qubits that are directly coupled to a waveguide. They generated two-photon N00N states and showed that the state and spatial entanglement of the emitted photons are tunable via the qubit frequencies. Using quadrature amplitude detection, they reconstructed the moments and correlations of the photonic modes and […]
Physicists create turnstile for photons
Phys.org September 22, 2020 If the quantum emitter is excited with laser light and fluoresces, it will always emit exactly one photon with each quantum leap. For this type of source, it is then still a challenge to efficiently “feed” the emitted photons into a glass fiber to send as many of them as possible to the receiver. An international team of researchers (Austria, Germany, Denmark) generated strongly correlated photon states using only weak coupling and taking advantage of dissipation. An ensemble of non-interacting waveguide-coupled atoms induces correlations between simultaneously arriving photons through collectively enhanced nonlinear interactions. These correlated photons […]
Revolutionary quantum breakthrough paves way for safer online communication
Phys.org September 2, 2020 An international team of researchers (UK, Austria, Croatia) used multiplexing which splits the light particles, emitted by a single system, so they can be received by multiple users efficiently. They designed a network for eight users using just eight receiver boxes As the user numbers grow, the logistics become increasingly unviable—for instance 100 users would take 9,900 receiver boxes. To demonstrate its functionality across distance the receiver boxes were connected to optical fibres via different locations across Bristol. The ability to transmit messages via quantum communication was tested using the city’s existing optical fibre network. The […]
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 […]
Trapped ytterbium ions could form backbone of a quantum internet, say researchers
Phys.org April 13, 2020 An international team of researchers (USA – University of Colorado, NIST, Caltech, Australia, Singapore) fabricated a periodic, nano-patterned 10 micron-long cavity with the ion at its centre. Light bounces back and forth many times in the cavity, greatly increasing the chance of the light interacting with the ion. The researchers then manipulated their ion qubit using laser and microwave pulses. The result is the emission of a photon that is entangled with the qubit – a photon that itself is a flying qubit of quantum information. More than 99% of the time, they found that this […]
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 […]
Soundwaves carry information between quantum systems
Nanowerk December 30, 2019 An international team of researchers ( USA- University of Chicago, UC Santa Barbara, Argonne National Laboratory, Japan) created a hybrid quantum system that acoustically drives transitions in electron spins. The experiment showed a basis for mechanical (strain) control. They developed a theoretical model from a combination of direct experimental observation and density functional theory calculations. From all of this information, they illustrated different types of mechanical strain that drive longer-lasting spins. The material studied was silicon carbide, which has been shown recently to support long-lived spin states that can be accessed optically. The results offer theoretical […]
China’s Quantum Satellite Security Has Been Broken
Next Big Future August 22, 2019 Although quantum key distribution (QKD) security can theoretically be unbreakable, the actual implementations are not perfect and have been broken. In a spree of publications thereafter, an international team of researchers (Norway, Germany) has now demonstrated several methods to successfully eavesdrop on commercial QKD systems based on weaknesses of avalanche photodiodes operating in gated mode. This has sparked research on new approaches to securing communications networks…read more. Open Access TECHNICAL ARTICLE