Lifeboat Foundation

(Phys.org)—One promising approach for scalable quantum computing is to use an all-optical architecture, in which the qubits are represented by photons and manipulated by mirrors and beam splitters. So far, researchers have demonstrated this method, called Linear Optical Quantum Computing, on a very small scale by performing operations using just a few photons. In an attempt to scale up this method to larger numbers of photons, researchers in a new study have developed a way to fully integrate single-photon sources inside optical circuits, creating integrated quantum circuits that may allow for scalable optical quantum computation.

The researchers, Iman Esmaeil Zadeh, Ali W. Elshaari, and coauthors, have published a paper on the integrated quantum circuits in a recent issue of Nano Letters.

As the researchers explain, one of the biggest challenges facing the realization of an efficient Linear Optical Quantum Computing system is integrating several components that are usually incompatible with each other onto a single platform. These components include a single-photon source such as quantum dots; routing devices such as waveguides; devices for manipulating photons such as cavities, filters, and quantum gates; and single-photon detectors.

In our last video we explained quantum annealing, and how the D-Wave system uses it for computation. In this new video we drill down into the physics of quantum annealing, and explain the concepts of the Hamiltonian and Eigenspectrum.

A team of researchers at the University of Ottawa has discovered that twisted light moves slower than the speed of light in a vacuum set by Einstein’s theory of relativity, with major implications for the development of quantum computing and communications.

The development of the logic gate had long been a stumbling block in the creation of functional quantum computers.

In 1937 Pyotr Kapitsa and John F. Allen discovered a strange behavior of ultracold liquids known as superfluidity. A superfluid is a fluid with no viscosity, basically a frictionless liquid. Without viscosity, the fluid has no way to dampen its motion. Because of this, superfluids have some pretty unusual behaviors. If a bit of superfluid is suspended in an open container, it will creep up along the walls, then drip down to a lower container. It can flow through tiny pores that regular liquids can’t, and can create fountains that could flow forever. This seeming defiance of gravity and common sense is due to the fact that its behavior is rooted in quantum physics. Though it is not a truly quantum state such as a Bose-Einstein condensate, it shares some commonality with it. In the lab, superfluids are only seen at temperatures barely above absolute zero. The most common example, helium-4, becomes superfluid when cooled below 2.17 K. So it might seem odd that superfluids are also found in the hot interiors of neutron stars.

A neutron star is a stellar remnant formed with a star runs out of hydrogen and heavier elements to fuse. After a star explodes as a supernova, the remaining core of the star collapses under its own weight to the point that only the pressure of nuclei can counter the force of gravity. A neutron star has a mass of about two Suns, but are only about 20 kilometers in diameter. They have a dense atmosphere of carbon only a few centimeters thick, and a thin crust of iron nuclei. In the interior of a neutron star, nuclei are pushed together ever more tightly, and reach a point where the nuclei can’t hold themselves together. As a result, individual neutrons “drip” out, and sink into the star’s core, forming a neutron fluid. As a neutron star cools, this neutron fluid transitions to a superfluid state. This happens not at a few degrees Kelvin, but at 500 to 800 million Kelvin. The interior of a neutron star is a hot superfluid sea.

Continue reading “The Quantum Fluid Inside Neutron Stars” »

Physicist John Martinis could deliver one of the holy grails of computing to Google—a machine that dramatically speeds up today’s applications and makes new ones possible.

Researchers from Griffith University and the University of Queensland have overcome one of the key challenges to quantum computing by simplifying a complex quantum logic operation. They demonstrated this by experimentally realising a challenging circuit—the quantum Fredkin gate—for the first time.

“The allure of quantum computers is the unparalleled processing power that they provide compared to current technology,” said Dr Raj Patel from Griffith’s Centre for Quantum Dynamics.

“Much like our everyday computer, the brains of a quantum computer consist of chains of logic gates, although quantum logic gates harness quantum phenomena.”

The classic quantum mechanics problem is a particle in a 1-D box. Here is a numerical solution to that problem.

Researchers from Griffith University and the University of Queensland have overcome one of the key challenges to quantum computing by simplifying a complex quantum logic operation. They demonstrated this by experimentally realising a challenging circuit — the quantum Fredkin gate — for the first time.

“The allure of quantum computers is the unparalleled processing power that they provide compared to current technology,” said Dr Raj Patel from Griffith’s Centre for Quantum Dynamics.

“Much like our everyday computer, the brains of a quantum computer consist of chains of logic gates, although quantum logic gates harness quantum phenomena.”

Continue reading “Unlocking the gates to quantum computing” »