Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: particle physics – Page 509

A new method allows the quantum state of atomic “qubits”—the basic unit of information in quantum computers—to be measured with twenty times less error than was previously possible, without losing any atoms. Accurately measuring qubit states, which are analogous to the one or zero states of bits in traditional computing, is a vital step in the development of quantum computers. A paper describing the method by researchers at Penn State appears March 25, 2019 in the journal Nature Physics.

“We are working to develop a quantum computer that uses a three-dimensional array of laser-cooled and trapped as qubits,” said David Weiss, professor of physics at Penn State and the leader of the research team. “Because of how works, the atomic qubits can exist in a ‘superposition’ of two states, which means they can be, in a sense, in both states simultaneously. To read out the result of a quantum computation, it is necessary to perform a measurement on each atom. Each measurement finds each atom in only one of its two possible states. The relative probability of the two results depends on the superposition state before the measurement.”

To measure qubit states, the team first uses lasers to cool and trap about 160 atoms in a three-dimensional lattice with X, Y, and Z axes. Initially, the lasers trap all of the atoms identically, regardless of their quantum state. The researchers then rotate the polarization of one of the laser beams that creates the X lattice, which spatially shifts atoms in one qubit state to the left and atoms in the other qubit state to the right. If an atom starts in a superposition of the two qubit states, it ends up in a superposition of having moved to the left and having moved to the right. They then switch to an X lattice with a smaller lattice spacing, which tightly traps the atoms in their new superposition of shifted positions. When light is then scattered from each atom to observe where it is, each atom is either found shifted left or shifted right, with a probability that depends on its initial state.

Read more

Physicists at EPFL propose a new “quantum simulator”: a laser-based device that can be used to study a wide range of quantum systems. Studying it, the researchers have found that photons can behave like magnetic dipoles at temperatures close to absolute zero, following the laws of quantum mechanics. The simple simulator can be used to better understand the properties of complex materials under such extreme conditions.

When subject to the laws of quantum mechanics, systems made of many interacting particles can display behaviour so complex that its quantitative description defies the capabilities of the most powerful computers in the world. In 1981, the visionary physicist Richard Feynman argued we can simulate such complex behavior using an artificial apparatus governed by the very same quantum laws – what has come to be known as a “.”

One example of a complex quantum system is that of magnets placed at really low temperatures. Close to absolute zero (−273.15 degrees Celsius), may undergo what is known as a “quantum phase transition.” Like a conventional phase transition (e.g. ice melting into water, or water evaporating into steam), the system still switches between two states, except that close to the transition point the system manifests quantum entanglement – the most profound feature predicted by . Studying this phenomenon in real materials is an astoundingly challenging task for .

Read more

Why do we exist? This is arguably the most profound question there is and one that may seem completely outside the scope of particle physics.

But our new experiment at CERN’s Large Hadron Collider has taken us a step closer to figuring it out.

To understand why, let’s go back in time some 13.8 billion years to the Big Bang. This event produced equal amounts of the matter you are made of and something called antimatter.

Read more

Astronomers observed a ghostly pulsar, a superdense, rapidly spinning neutron star exploded from a supernova 10,000 years ago, racing through space at nearly 2.5 million miles an hour—so fast it could travel the distance between Earth and the Moon in just 6 minutes. The discovery was made using NASA’s Fermi Gamma-ray Space Telescope and the National Science Foundation’s Karl G. Jansky Very Large Array (VLA).

The pulsar lies about 53 light-years from the center of a supernova remnant called CTB 1. Its rapid motion through interstellar gas results in shock waves that produce the tail of magnetic energy and accelerated particles detected at radio wavelengths using the VLA. The tail extends 13 light-years and clearly points back to the center of CTB 1.

This one, dubbed PSR J0002+6216 (J0002 for short), sports a radio-emitting tail pointing directly toward the expanding debris of a recent supernova explosion. “Thanks to its narrow dart-like tail and a fortuitous viewing angle, we can trace this pulsar straight back to its birthplace,” said Frank Schinzel, a scientist at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. “Further study of this object will help us better understand how these explosions are able to ‘kick’ neutron stars to such high speed.”

Read more

In February, the CMS and MoEDAL collaborations at CERN signed an agreement to hand over to MoEDAL a section of the LHC beam pipe that was located inside CMS between 2008 and 2013. The delicate object, 6 metres long and made of beryllium, will now be sliced and fed into a highly precise magnetic sensors in order to allow MoEDAL to look for magnetic monopoles: hypothetical particles with only a single magnetic pole – north or south – unlike north-south dipoles we are familiar with.

Paul Dirac posited the existence of magnetic monopoles in 1931, and, although never observed, they could be produced in collisions within the LHC. They would not travel very far after being produced, binding with the beryllium nuclei of the beam pipe and remaining there awaiting discovery.

The MoEDAL collaboration will cut the beam pipe at a special facility at the Centre for Particle Physics at the University of Alberta in Canada and ship the pieces back across the Atlantic to ETH Zurich in Switzerland to look for electromagnetic anomalies in them. Many theories attempting to unify all of the known forces into a single force (so-called “Grand Unified Theories”) require the existence of monopoles and finding them could open the door to all-new physics.

Read more

Up until now, the ability to make gray goo has been theoretical. However, the scientists at the Columbia University School of Engineering and Applied Science have made a significant breakthrough. The individual components are computationally simple but can exhibit complex behavior.

Current robots are usually self-contained entities made of interdependent subcomponents, each with a specific function. If one part fails, the robot stops working. In robotic swarms, each robot is an independently functioning machine.

In a new study published today in Nature, researchers at Columbia Engineering and MIT Computer Science & Artificial Intelligence Lab (CSAIL), demonstrate for the first time a way to make a robot composed of many loosely coupled components, or “particles.” Unlike swarm or modular robots, each component is simple, and has no individual address or identity. In their system, which the researchers call a “particle robot,” each particle can perform only uniform volumetric oscillations (slightly expanding and contracting), but cannot move independently.

The team, led by Hod Lipson, professor of mechanical engineering at Columbia Engineering, and CSAIL Director Daniela Rus, discovered that when they grouped thousands of these particles together in a “sticky” cluster and made them oscillate in reaction to a light source, the entire particle robot slowly began to move forward, towards the light.

Continue reading “Robotic ‘gray goo’” | >

In quantum physics, particles can ’tunnel’ through seemingly impenetrable barriers, even when they apparently don’t have the energy to do so. Now, researchers have gleaned behind the curtain to better understand how this trick is done.

This problem has puzzled scientists for decades – in particular, the time it takes for particles to do their quantum tunnelling, and get from one side of a barrier to another.

In the case of the atomic hydrogen particles used in these experiments, the researchers found that it happens instantaneously.

Read more