Quantum leap: Photon discovery is a major step toward at-scale quantum technologies

EurekAlert  May 20, 2020 Architectures for photonic quantum computing place stringent demands on high quality information carriers. An international team of researchers (UK, Italy) has fabricated on-chip photon sources and demonstrated that they meet the computing requirements. The photon sources are fabricated in silicon using mature processes and exploit a dual-mode pump-delayed excitation scheme to engineer the emission of spectrally pure photon pairs through inter-modal spontaneous four-wave mixing in low-loss spiraled multi-mode waveguides. They measured a spectral purity of 0.9904 ± 0.0006, a mutual indistinguishability of 0.987 ± 0.002, and >90% intrinsic heralding efficiency and on-chip quantum interference with a visibility of 0.96 ± 0.02 between […]

Army researchers see path to quantum computing at room temperature

EurekAlert  May 1, 2020 Researchers at MIT show that relatively simple integrated photonic circuits have the potential to realize a high fidelity deterministic controlled-phase gate between photonic qubits using bulk optical nonlinearities. The gate is enabled by converting travelling continuous-mode photons into stationary cavity modes using strong classical control fields that dynamically change the effective cavity-waveguide coupling rate. This architecture reduces the wave packet distortions that otherwise accompany the action of optical nonlinearities. They show that dynamically coupled cavities enable a trade-off between errors due to loss and wave packet distortion. The proposed architecture represents a new approach only relies […]

Weaving quantum processors out of laser light

Science Daily  October 17, 2019 The approach taken by an international team of researchers (Japan, Australia, USA – University of New Mexico) starts with extreme scalability, built in from the very beginning, because the processor, called a cluster state is made of light. A cluster state is a large collection of entangled quantum components that performs quantum computations when measured in a particular way. To be useful for real-world problems, a cluster state must be both large enough and have the right entanglement structure. To make the cluster state, specially designed crystals convert ordinary laser light into quantum light called […]

This New Chip Could Bridge The Gap Between Classical And Quantum Computing

Science Alert  September 28, 2019 An international team of researchers (USA – Purdue University, Japan) has developed hardware for a ‘probabilistic computer’ which solves quantum problems using a p-bit which can only be a 1 or a 0, but they can switch between those two states very quickly and p-bits work at room temperature. By carefully controlling these fluctuations, scientists can tackle calculations of a kind that are generally considered to be quantum computing problems. They modified MRAM device to present a proof-of-concept experiment for probabilistic computing. Factorization of integers up to 945 was demonstrated using eight correlated p-bits, and […]

Team closes in on ‘holy grail’ of room temperature quantum computing chips

Phys.org  September 18, 2019 Researchers at the Stevens Institute of Technology have coaxed photons into interacting by firing a laser beam into a racetrack-shaped microcavity carved into a sliver of crystal. As the laser light bounces around the racetrack, its confined photons interact with one another, producing a harmonic resonance that causes some of the circulating light to change wavelength. They boosted its efficiency by using a chip made from lithium niobate on insulator. They used an ion-milling tool to etch a tiny racetrack. The team has already identified ways to increase their Q-factor by a factor of at least […]

Scientists discover new state of matter

Phys.org  August 15, 2019 A team of researchers in the US (New York University, Wayne State University, SUNY Buffalo) have shown the experimental evidence for a topological superconductivity. They analyzed a transition of quantum state from its conventional state to a new topological state, measuring the energy barrier between these states focusing on majorana particles. Majorana particles have the potential to store quantum information in a special computation space where quantum information is protected from the environment noise. As there is no natural host material for these particles the new form of matter provides a platform on which these calculations […]

Physicists use light waves to accelerate supercurrents, enable ultrafast quantum computing

Science Daily  July 1, 2019 A team of researchers in the US (Iowa State University, University of Wisconsin, University of Alabama at Birmingham) is finding new macroscopic supercurrent flowing states and developing quantum controls for switching and modulating them. Experimental data obtained from a terahertz spectroscopy instrument indicates terahertz light-wave tuning of supercurrents is a universal tool and key for pushing quantum functionalities to reach their ultimate limits in many cross-cutting disciplines, design of emergent materials properties and collective coherent oscillations for quantum engineering applications…read more. TECHNICAL ARTICLES 

New holographic technique opens the way for quantum computation

Eurekalert  May 3, 2019 An international team of researchers (Switzerland, UK, Spain) shows that holograms of local electromagnetic fields can be obtained with combined attosecond/nanometer resolution in an ultrafast transmission electron microscope. Unlike conventional holography, where signal and reference are spatially separated and then recombined to interfere, our method relies on electromagnetic fields to split an electron wave function in a quantum coherent superposition of different energy states. In the image plane, spatial modulation of the electron energy distribution reflects the phase relation between reference and signal fields. Beyond imaging applications, this approach allows implementing quantum measurements in parallel, providing […]

The Case Against Quantum Computing

IEEE Spectrum  November 15, 2018 A useful quantum computer needs to process a set of continuous parameters that is larger than the number of subatomic particles in the observable universe. According to researchers in France while experimental research is beneficial and may lead to a better understanding of complicated quantum systems, they are skeptical that these efforts will ever result in a practical quantum computer. Such a computer would have to be able to manipulate—on a microscopic level and with enormous precision—a physical system characterized by an unimaginably huge set of parameters, each of which can take on a continuous […]

Quantum bugs, meet your new swatter

Science Daily  August 20, 2018 According to a team of researchers in the US (Rice University, University of Maryland, industry, UT Austin) when a quantum computer executes an algorithm, it starts at a specific state. The state at the very end is the answer to the algorithm’s question. Reassembling the full state from these measurements, one can later pinpoint hardware or software errors that may have caused the computer to deliver unexpected results. However, the computational cost of reconstruction can be high even as few as five or six qubits. The team solved the validation problem with an algorithm they […]