EurekAlert February 18, 2021 The application of active error correction in a quantum computer is very complex and comes with an extensive use of hardware. An international team of researchers (Germany, Switzerland, the Netherlands) has proposed a design for a circuit with passive error correction. The circuit is designed in such a way that it is already inherently protected against environmental noise while still controllable. The concept thus bypasses the need for active stabilization in a highly hardware-efficient manner and would therefore be a promising candidate for a future large-scale quantum processor that has many qubits. By implementing a gyrator […]
Category Archives: Quantum communication
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, […]
Sharing a secret…the quantum way
Science Daily July 31, 2020 By taking advantage of the high‐dimensional Hilbert space for orbital angular momentum and using Perfect Vortex beams as their carriers, researchers in South Africa have presented a proof‐of‐principle implementation of a high‐dimensional quantum secret sharing scheme. This scheme is experimentally implemented with a fidelity of 93.4%, for 10 participants in =11 dimensions. The implementation can easily be scaled to higher dimensions and any number of participants, opening the way for securely distributing information across a network of nodes…read more. TECHNICAL ARTICLE
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 […]
New techniques improve quantum communication, entangle phonons
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 […]
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. […]