Quantum systems learn joint computing

Phy.org  February 5, 2021 The big challenge in quantum computing is to realize scalable multi-qubit systems with cross-talk–free addressability and efficient coupling of arbitrarily selected qubits. Quantum networks promise a solution by integrating smaller qubit modules to a larger computing cluster. Such a distributed architecture, however, requires the capability to execute quantum-logic gates between distant qubits. An international team of researchers (Germany, Spain) experimentally realized such a gate over 60 meters. They employed an ancillary photon that they successively reflected from two remote qubit modules, followed by a heralding photon detection, which triggers a final qubit rotation. They used the […]

Laser loop couples quantum systems over a distance

Science Daily  May 7, 2020 An international team of researchers (Switzerland, Germany) used laser light to couple the vibrations of a 100 nanometer thin membrane to the motion of the spin of atoms over a distance of one meter. As a result, each vibration of the membrane sets the spin of the atoms in motion and vice versa. In this laser loop, the properties of the light can be controlled such that no information about the motion of the two systems is lost to the environment, thus ensuring that the quantum mechanical interaction is not disturbed. It is possible to […]

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 […]

How a new quantum approach can develop faster algorithms to deduce complex networks

EurekAlert  March 3, 2020 Complex networks form the basis of various applications in virtually all fields of science. To analyze and manipulate these networks, specific “search” algorithms are required. But conventional search algorithms are slow and, when dealing with large networks, require a long computational time. To develop more efficient quantum algorithms researchers in Japan performed numerical simulations on some basic fractal lattices to try to find out the relationship between the number of vertices and the optimal computational time in a quantum walk search. They confirmed that the scaling law for some fractal lattices varied according to their spectral […]

Longest microwave quantum link

Phys.org  March 5, 2020 Currently there are computers with a few dozen qubits, but several hundreds of thousands of them are almost impossible to accommodate in existing devices as they need to be cooled down to temperatures close to the absolute zero of -273,15 degrees Celsius. To connect two superconducting quantum chips to exchange superposition states between them with minimal decoherence researchers in Germany cooled the chips to a few hundredths of a degree above absolute zero and demonstrated that the quantum link can be sufficiently cooled down to reliably transmit quantum information between two quantum chips. They will report […]

On the way to quantum networks

Phys.org  January 24, 2020 Entanglement between stationary quantum memories and photonic channels is the essential resource for future quantum networks. Together with entanglement distillation, it will enable efficient distribution of quantum states. Researchers in Germany entangled a rubidium atom with a photon and were able to detect the entangled state—which now shares the quantum properties of both particles—after its passage through a 20-km coil of optic fiber. Rubidium atoms emit photons with a wavelength of 780 nanometers which is rapidly absorbed. They built a quantum frequency converter that was specifically designed to increase the wavelength of the emitted photons from […]