Phys.org February 11, 2022 Spins in two-dimensional materials offer an advantage, as the reduced dimensionality enables feasible on-chip integration into devices. An international team of researchers (UK, Australia) has reported room-temperature optically detected magnetic resonance (ODMR) from single carbon-related defects in hexagonal boron nitride with up to 100 times stronger contrast than the ensemble average. They identified two distinct bunching timescales in the second-order intensity-correlation measurements for ODMR-active defects, but only one for those without an ODMR response. They observed either positive or negative ODMR signal for each defect. Based on kinematic models, they related this bipolarity to highly tunable […]
Tag Archives: Quantum technology
Cooling matter from a distance
Science Daily February 2, 2022 Researchers in Switzerland succeeded in forming a control loop consisting of two quantum systems separated by one meter. Within this loop a vibrating membrane was cooled by a cloud of atoms, and the two systems were coupled to one another by laser light. As one of the systems acts as a control unit for the other, no measurement is needed. Instead, the control system is configured to bring the target system into a desired state by means of coherent quantum mechanical interaction. They successfully used this coherent feedback mechanism to reduce the temperature of the […]
New approach transports trapped ions to create entangling gates
Phys.org January 28, 2022 Trapped ions excited with a laser beam can be used to create entangled qubits in quantum information systems but addressing several stationary pairs of ions in a trap requires multiple optical switches and complex controls. Researchers at Georgia Tech Research Institute moved calcium ions held in a surface electrode trap through a stationary bichromatic optical beam potentially integrating the existing transport control into quantum logic operations. Measurements showed that the entangled quantum state of the two qubits transported through the optical beam had a fidelity comparable to entangled states produced by stationary gates performed in the […]
Twin-field quantum key distribution (QKD) across an 830-km fibre
Phys.org January 24, 2022 As the photons carrying signals cannot be amplified or relayed via classical optical techniques to maintain quantum security, the transmission loss of the channel limits its achievable distance. An international team of researchers (Spain, Japan, Canada, China, Russia) has designed an experimental QKD system that could tolerate a channel loss beyond 140 dB and obtain a secure distance of 833.8 km. Furthermore, the optimized four-phase twin-field protocol and set-up make its secure key rate more than two orders of magnitude greater than previous records over similar distances… read more. TECHNICAL ARTICLE 1 , Open Access 2
Mini electricity generator made from quantum dots
Phys.org January 18, 2022 The major challenges toward the exploitation of graphene nanoribbons (GNRs) in electronic applications include reliable contacting, and the preservation of their physical properties upon device integration. An international team of researchers (Switzerland, UK, Germany) described the quantum dot behavior of atomically precise GNRs integrated in a device geometry. The devices consist of a film of aligned five-atom-wide GNRs (5-AGNRs) transferred onto graphene electrodes with a sub 5 nm nanogap. They demonstrated that the narrow-bandgap 5-AGNRs exhibit metal-like behavior at room temperature and single-electron transistor behavior for temperatures below 150 K. They obtained addition energies in the […]
Building a silicon quantum computer chip atom by atom (w/video)
Nanowerk January 12, 2022 Until now, implanting atoms in silicon has been a haphazard process, where a silicon chip gets showered with phosphorus which implant in a random pattern. An international team of researchers (Australia, Germany) has developed a technique to place them in an orderly array, similar to the transistors in conventional semiconductors computer chips. They embedded phosphorus ions, precisely counting each one, in a silicon substrate creating a qubit using advanced technology developed for sensitive x-ray detectors and a special atomic force microscope. They drilled a tiny hole in the cantilever, so that when it was showered with phosphorus […]
A new look at quantum radar suggests it might boost accuracy more than thought
Phys.org January 10, 2022 Despite the many proposals for quantum radar, none have delineated the ultimate quantum limit on ranging accuracy. A team of researchers in the US (University of Arizona, MIT) has derived that limit through continuous-time quantum analysis. They showed that quantum illumination ranging—a quantum pulse-compression radar that exploits the entanglement between a high time-bandwidth product transmitted signal pulse and a high time-bandwidth product retained idler pulse—achieves that limit. They also showed that quantum illumination ranging offers mean-squared range-delay accuracy that can be tens of dB better than that of a classical pulse-compression radar of the same pulse […]
Experimental quantum teleportation of propagating microwaves
Phys.org January 4, 2022 Recent breakthroughs in quantum computation with superconducting circuits trigger a demand for quantum communication channels between spatially separated superconducting processors operating at microwave frequencies. An international team of researchers (Germany, Austria) demonstrated the unconditional quantum teleportation of propagating coherent microwave states by exploiting two-mode squeezing and analog feedforward over a macroscopic distance of d = 0.42 m. They achieved a teleportation fidelity of F = 0.689 ± 0.004, exceeding the asymptotic no-cloning threshold. Thus, the quantum nature of the teleported states is preserved, opening the avenue toward unconditional security in microwave quantum communication. As their principal teleportation […]
A-list candidate for fault-free quantum computing delivers surprise
Science Daily December 22, 2021 Spin-triplet pairing is important because it can host topological states and majorana fermions relevant for quantum computation. Because spin-triplet pairing is usually mediated by ferromagnetic (FM) spin fluctuations, uranium-based materials near an FM instability are ideal candidates for realizing spin-triplet superconductivity. UTe2 has been identified as a candidate for a chiral spin-triplet topological superconductor near an FM instability, although it also has antiferromagnetic (AF) spin fluctuations. A team of researchers in the US (Rice University, Florida State University, Oak Ridge National Laboratory, UC San Diego, Arizona State University) used inelastic neutron scattering (INS) to show […]
Scientists document the presence of quantum spin liquids, a never-before-seen state of matter
Phys.org December 2, 2021 To reproduce the microscopic physics found in condensed matter systems an international team of researchers (USA – Harvard University, MIT, Austria) used a simulator that allows the researchers to create programmable shapes like squares, honeycombs, or triangular lattices to engineer different interactions and entanglements between ultracold atoms. Quantum spin liquids display none of that magnetic order because, essentially, there is a third spin added, turning the checker box pattern to a triangular pattern making it a “frustrated” magnet where the electron spins can’t stabilize in a single direction. The researchers used the simulator to create their […]