Phys.org December 3, 2021 Creating entangled photons can be a difficult task requiring a complicated setup as non-classical kinds of light have a small number of photons. In a new scheme researchers at the University of Chicago used two different sources to simultaneously emit photons into a cavity that has an extremely weak nonlinearity. With careful tuning, these sources then cancel each other out with destructive interference—creating a “wall” that blocks photons—once the selected number of photons are captured in the cavity. The basic mechanism can also be applied to all electromagnetic radiation. It can be used to generate and […]
Category Archives: Quantum technology
All-nitride superconducting qubit made on a silicon substrate
Science Daily September 20, 2021 Researchers in Japan have developed superconducting qubits based on NbN/AlN/NbN epitaxial Josephson junctions on silicon substrates which promise to overcome the drawbacks of qubits based on Al/AlOx/Al junctions. The all-nitride qubits have great advantages such as chemical stability against oxidation, resulting in fewer two-level fluctuators, feasibility for epitaxial tunnel barriers that reduce energy relaxation and dephasing, and a larger superconducting gap of ~5.2 meV for NbN, compared to ~0.3 meV for aluminum, which suppresses the excitation of quasiparticles. By replacing conventional MgO by a silicon substrate with a TiN buffer layer for epitaxial growth of […]
New quantum research gives insights into how quantum light can be mastered
Phys.org July 22, 2021 Researchers at Los Alamos National Laboratory propose that modulated quantum metasurfaces can control all properties of photonic qubits, a breakthrough that could impact the fields of quantum information, communications, sensing and imaging, as well as energy and momentum harvesting. They developed a metasurface that looked like an array of rotated crosses, then proposed to shoot a single photon through the metasurface, where the photon splits into a superposition of many colors, paths, and spinning states generating quantum entanglement meaning the single photon can inherit different properties at once. According to the researchers by manipulating these properties, […]
The quantum refrigerator
Science Daily July 29, 2021 An international team of researchers (Germany, Austria, Portugal, Singapore) has provided a detailed proposal of how to realize a quantum machine in one-dimensional ultracold atomic gases, which consists of a set of modular operations giving rise to a piston. These can then be coupled sequentially to thermal baths, with the innovation that a quantum field takes up the role of the working fluid. They proposed models for compression on the system to use it as a piston and coupling to a bath that gives rise to a valve controlling heat flow. By composing the numerically […]
The era of single-spin color centers in silicon carbide is approaching
Phys.org July 19, 2021 The spin color centers in silicon carbide, including silicon vacancies and divacancies have excellent optical and spin properties. Researchers in China have presented the coherent manipulation of single divacancy spins in 4H-SiC with a high readout contrast (−30%) and a high photon count rate under ambient conditions, which are competitive with the nitrogen-vacancy centres in diamond. Coupling between a single defect spin and a nearby nuclear spin is also observed. They provided a theoretical explanation for the high readout contrast by analysing the defect levels and decay paths. Since the high readout contrast is important in […]
A quantum step to a heat switch with no moving parts
Science Daily June 7, 2021 Based on foundational theory a team of researchers in the US (Iowa State University, University of Ohio, University of Chicago) engineered an alloy with the elements bismuth and antimony at precise ranges. In this material electrons move like massless photons, a phenomenon theoretically predicted to exist. Under the influence of an external magnetic field some of the electrons generate energy, while others absorb energy, effectively turning the material into an energy pump resulting in 300% increase in its thermal conductivity. The mechanism is turned off if the magnet is taken away. This property, and the […]
Scientists harness molecules into single quantum state
Science Daily April 28, 2021 For molecules to reach the quantum regime usually requires efficient cooling at high densities, which is frequently hindered by fast inelastic collisions that heat and deplete the population of molecules. An international team of researchers (USA- University of Chicago, China) prepared two-dimensional Bose–Einstein condensates of spinning molecules by inducing pairing interactions in an atomic condensate near a g-wave Feshbach resonance. The trap geometry and the low temperature of the molecules help to reduce inelastic loss, ensuring thermal equilibrium. They investigated the unpairing dynamics in the strong coupling regime and found that near the Feshbach resonance […]
Remote control for quantum emitters
Science Daily March 12, 2021 An international team of researchers (Austria, Spain) developed a method to individually address quantum emitters using tailored light pulses based on chirped light. In structures with certain electromagnetic properties, such as waveguides, the frequencies propagate at different speeds. If the initial conditions of the light pulse is correctly set, the pulse compresses itself at a certain distance. They analytically describe how the compression distance and width of the pulse can be tuned through its initial parameters. They showed that the interaction of such pulses with a quantum emitter is highly sensitive to its position due […]
New quantum theory heats up thermodynamic research
Phys.org March 5, 2021 The classical Gibbs paradox concerns the entropy change upon mixing two gases. Whether an observer assigns an entropy increase to the process depends on their ability to distinguish the gases. Moving the thought experiment into the quantum realm researchers in the UK have shown that the ignorant observer can extract work from mixing different gases, even if the gases cannot be directly distinguished. In the macroscopic limit, the quantum case diverges from the classical ideal gas: as much work can be extracted as if the gases were fully distinguishable. They showed that the ignorant observer assigns […]
Heat-free optical switch would enable optical quantum computing chips
Nanowerk March 3, 2021 In quantum integrated photonics integrated detectors offer optical readout and when interfaced with reconfigurable circuits, allow feedback and adaptive control, crucial for deterministic quantum teleportation, training of neural networks, and stabilization of complex circuits. However, the heat generated by thermally reconfigurable photonics is incompatible with heat-sensitive superconducting single-photon detectors, and thus their on-chip co-integration remains elusive. An international team of researchers (Sweden, Austria) has designed low-power microelectromechanical reconfiguration of integrated photonic circuits interfaced with superconducting single-photon detectors on the same chip. They demonstrated three key functionalities for photonic quantum technologies: 28 dB high-extinction routing of classical […]