Phys.org April 15, 2024 Nonlocality is crucial for device-independent technologies like quantum key distribution and randomness generation. It quickly deteriorates in the presence of noise, and restoring nonlocal correlations requires additional resources incurring a significant resource overhead. An international team of researchers (Australia, France, USA – NIST, Boulder, CO) experimentally demonstrated that single copies of Bell-local states, incapable of violating any standard Bell inequality, could give rise to nonlocality after being embedded into a quantum network of multiple parties. They subjected the initial entangled state to a quantum channel that broadcast part of the state to two independent receivers and […]
Tag Archives: Quantum network
Discovery may enable network interface for quantum computers
Phys.org October 5, 2023 The coupling of microwave and optical systems presents a challenge due to the natural incompatibility of energies, but potential applications range from optical interconnects for quantum computers to next-generation quantum microwave sensors, detectors, and coherent imagers. Emerging platforms are constrained by specific conditions. An international team of researchers (Poland, Denmark) designed a set-up using Rydberg atoms that allows wideband coupling of optical and microwave photons at room temperature. They demonstrated continuous-wave conversion of a 13.9 GHz field to a near-infrared optical signal using an ensemble of Rydberg atoms via a free-space six-wave mixing process designed to minimize […]
Researchers demonstrate secure information transfer using spatial correlations in quantum entangled beams of light
Phys.org June 5, 2023 The ability to use the temporal and spatial degrees of freedom of quantum states of light to encode and transmit information is crucial for a robust and efficient quantum network. However, the potential offered by the large dimensionality of the spatial degree of freedom remains unfulfilled, as the necessary level of control required to encode information remains elusive. Researchers at the University of Oklahoma encoded information in the distribution of the spatial correlations of entangled twin beams by taking advantage of their dependence on the angular spectrum of the pump needed for four-wave mixing. They showed […]
Erbium atoms in silicon: A prime candidate for quantum networks
Phys.org November 7, 2022 A major challenge for a scalable architecture for quantum information processing is based on emitters in nanostructures that are coupled by light. Researchers in Germany demonstrated the integration of erbium atoms with special optical properties into a silicon crystal. Thus, the atoms could be connected by light at a wavelength that is commonly used in telecommunications, making them ideal building blocks for future quantum networks that enable calculations with several quantum computers, as well as the secure exchange of data in a quantum internet. They achieved a narrow inhomogeneous broadening, less than 1 GHz, strong optical […]
The entanglement of two quantum memory systems 12.5 km apart from each other
Phys.org August 16, 2022 Researchers in China have reported the establishment of post selected entanglement between two atomic quantum memories physically separated by 12.5 km. They created atom-photon entanglement in one node and sent the photon to a second node for storage via electromagnetically induced transparency. They harnessed low-loss transmission through a field-deployed fiber of 20.5 km by making use of frequency down-conversion and up-conversion. The final memory-memory entanglement was verified to have a fidelity of 90% via retrieving to photons. According to the researchers their experiment makes a significant step forward toward the realization of a practical metropolitan-scale quantum […]
Quantum network nodes with warm atoms
Science Daily June 24, 2022 An international team of researchers (Switzerland, Germany) built and successfully interfaced a single-photon source based on cavity-enhanced spontaneous parametric down-conversion in periodically poled potassium titanyl phosphate and a matched memory based on electromagnetically induced transparency in warm 87Rb vapor. The bandwidth of the photons emitted by the source was 370MHz, which is within the accepted bandwidth of the memory. The experimental complexity was kept low, with all components operating at or above room temperature. Read-out noise of the memory was considerably reduced by exploiting polarization selection rules in the hyperfine structure of spin-polarized atoms. They […]
Researchers confront major hurdle in quantum computing
Phys.org May 5, 2021 To realize the full potential of quantum computing high-fidelity information transfer mechanisms are required for quantum error correction and efficient algorithms – and that presents a major experimental challenge. A team of researchers in the US (University of Rochester, Virginia Tech, Purdue University) demonstrated adiabatic quantum state transfer (AQT) which is not affected by pulse errors and noise. They exploited entanglement even when the particles are separated by a large distance to transfer one electron’s quantum spin state across a chain of four electrons in semiconductor quantum dots. AQT is robust against pulse errors and noise. […]
Using drones to create local quantum networks
Phys.org January 18, 2021 Researchers in China built a small laser-generating device and affixed it to one of the drones. As it fired, photons were split in two, creating entangled pairs. One of the paired photons was directed toward another drone while the other was directed to a ground station. The drone that received the entangled photon served only as a relay—after refocusing, the photon was forwarded to a third drone, which then sent it to a second ground station. Motorized devices were used on the drones to ensure transmitters and received lined up properly for transmission of the entangled […]
An electrical trigger fires single, identical photons
Phys.org October 8, 2020 An international team of researchers (USA – Lawrence Berkeley National Laboratory, Montana State University, Spain) has demonstrated electrically stimulated photon emission from individual atomic defects in monolayer WS2 and directly correlated the emission with the local atomic and electronic structure. Radiative transitions are locally excited by sequential inelastic electron tunneling from a metallic tip into selected discrete defect states in the WS2 bandgap. Coupling to the optical far field is mediated by tip plasmons, which transduce the excess energy into a single photon. The applied tip-sample voltage determines the transition energy. Inelastic charge carrier injection into […]
Quantum-entangled light from a vibrating membrane
Phys.org March 31, 2020 Optical quantum states propagate with ultralow attenuation and resilient to ubiquitous thermal noise. Mechanical systems are envisioned as versatile interfaces between photons and a variety of solid-state quantm information processing platforms. Researchers in Denmark generated entanglement between two propagating optical modes by coupling them to the same cryogenic mechanical system. The entanglement persisted at room temperature. They verified the inseparability of the bipartite state and fully characterized its logarithmic negativity by homodyne tomography. Combined with quantum interfaces between mechanical systems and solid-state qubit processors, this paves the way for mechanical systems enabling long-distance quantum information networking […]