Quantum computer as detector shows space is not squeezed

As the Earth rotates every 24 hours, the orientation of the ions in the quantum computer/detector changes with respect to the Sun’s rest frame. If space were squeezed in one direction and not another, the energies of the electrons in the ions would have shifted with a 12-hour period. (Hartmut Haeffner image)

A new experiment by UC Berkeley physicists used partially entangled atoms — identical to the qubits in a quantum computer — to demonstrate more precisely than ever before that this is true, to one part in a billion billion.

The classic experiment that inspired Albert Einstein was performed in Cleveland by Albert Michelson and Edward Morley in 1887 and disproved the existence of an “ether” permeating space through which light was thought to move like a wave through water. What it also proved, said Hartmut Häffner, a UC Berkeley assistant professor of physics, is that space is isotropic and that light travels at the same speed up, down and sideways.

“Michelson and Morley proved that space is not squeezed,” Häffner said. “This isotropy is fundamental to all physics, including the Standard Model of physics. If you take away isotropy, the whole Standard Model will collapse. That is why people are interested in testing this.”

The Standard Model of particle physics describes how all fundamental particles interact, and requires that all particles and fields be invariant under Lorentz transformations, and in particular that they behave the same no matter what direction they move.

Häffner and his team conducted an experiment analogous to the Michelson-Morley experiment, but with electrons instead of photons of light. In a vacuum chamber he and his colleagues isolated two calcium ions, partially entangled them as in a quantum computer, and then monitored the electron energies in the ions as Earth rotated over 24 hours.

If space were squeezed in one or more directions, the energy of the electrons would change with a 12-hour period. It didn’t, showing that space is in fact isotropic to one part in a billion billion (1018), 100 times better than previous experiments involving electrons, and five times better than experiments like Michelson and Morley’s that used light.

The results disprove at least one theory that extends the Standard Model by assuming some anisotropy of space, he said.

Häffner and his colleagues, including former graduate student Thaned Pruttivarasin, now at the Quantum Metrology Laboratory in Saitama, Japan, will report their findings in the Jan. 29 issue of the journal Nature.

Entangled qubits

Häffner came up with the idea of using entangled ions to test the isotropy of space while building quantum computers, which involve using ionized atoms as quantum bits, or qubits, entangling their electron wave functions, and forcing them to evolve to do calculations not possible with today’s digital computers. It occurred to him that two entangled qubits could serve as sensitive detectors of slight disturbances in space.

“I wanted to do the experiment because I thought it was elegant and that it would be a cool thing to apply our quantum computers to a completely different field of physics,” he said. “But I didn’t think we would be competitive with experiments being performed by people working in this field. That was completely out of the blue.”

He hopes to make more sensitive quantum computer detectors using other ions, such as ytterbium, to gain another 10,000-fold increase in the precision measurement of Lorentz symmetry. He is also exploring with colleagues future experiments to detect the spatial distortions caused by the effects of dark matter particles, which are a complete mystery despite comprising 27 percent of the mass of the universe.

“For the first time we have used tools from quantum information to perform a test of fundamental symmetries, that is, we engineered a quantum state which is immune to the prevalent noise but sensitive to the Lorentz-violating effects,” Häffner said. “We were surprised the experiment just worked, and now we have a fantastic new method at hand which can be used to make very precise measurements of perturbations of space.”

Other co-authors are UC Berkeley graduate student Michael Ramm, former UC Berkeley postdoc Michael Hohensee of Lawrence Livermore National Laboratory, and colleagues from the University of Delaware and Maryland and institutions in Russia. The work was supported by the National Science Foundation.

Source: UC Berkeley

NASA's Dawn Spacecraft Captures Best-Ever View of Dwarf Planet

This animation of the dwarf planet Ceres was made by combining images taken by the Dawn spacecraft on January 25, 2015.

NASA's Dawn spacecraft has returned the sharpest images ever seen of the dwarf planet Ceres. The images were taken 147,000 miles (237,000 kilometers) from Ceres on Jan. 25, and represent a new milestone for a spacecraft that soon will become the first human-made probe to visit a dwarf planet.

"We know so little about our vast solar system, but thanks to economical missions like Dawn, those mysteries are being solved," said Jim Green, Planetary Science Division Director at NASA Headquarters in Washington.

At 43 pixels wide, the new images are more than 30 percent higher in resolution than those taken by NASA's Hubble Space Telescope in 2003 and 2004 at a distance of over 150 million miles (about 241 million kilometers). The resolution is higher because Dawn is traveling through the solar system to Ceres, while Hubble remains fixed in Earth orbit. The new Dawn images come on the heels of initial navigation images taken Jan. 13 that reveal a white spot on the dwarf planet and the suggestion of craters. Hubble images also had glimpsed a white spot on the dwarf planet, but its nature is still unknown.

"Ceres is a 'planet' that you've probably never heard of," said Robert Mase, Dawn project manager at NASA's Jet Propulsion Laboratory in Pasadena, California. "We're excited to learn all about it with Dawn and share our discoveries with the world."

As the spacecraft gets closer to Ceres, its camera will return even better images. On March 6, Dawn will enter into orbit around Ceres to capture detailed images and measure variations in light reflected from Ceres, which should reveal the planet's surface composition.

"We are already seeing areas and details on Ceres popping out that had not been seen before. For instance, there are several dark features in the southern hemisphere that might be craters within a region that is darker overall," said Carol Raymond, deputy principal investigator of the Dawn mission at JPL. "Data from this mission will revolutionize our understanding of this unique body. Ceres is showing us tantalizing features that are whetting our appetite for the detailed exploration to come."

Ceres, the largest body between Mars and Jupiter in the main asteroid belt, has a diameter of about 590 miles (950 kilometers). Some scientists believe the dwarf planet harbored a subsurface ocean in the past and liquid water may still be lurking under its icy mantle.

Originally described as a planet, Ceres was later categorized as an asteroid, and then reclassified as a dwarf planet in 2006. The mysterious world was discovered in 1801 by astronomer Giuseppe Piazzi, who named the object for the Roman goddess of agriculture, grain crops, fertility and motherly relationships.

"You may not realize that the word 'cereal' comes from the name Ceres. Perhaps you already connected with the dwarf planet at breakfast today," said JPL's Marc Rayman, mission director and chief engineer of the Dawn mission.

Powered by a uniquely capable ion propulsion system, Dawn also orbited and explored Vesta, the second most massive body in the asteroid belt. From 2011 to 2012, Dawn returned more than 30,000 images, 18 million light measurements and other scientific data about the impressive large asteroid. Vesta has a diameter of about 326 miles (525 kilometers).

"With the help of Dawn and other missions, we are continually adding to our understanding of how the solar system began and how the planets were formed," said Chris Russell, principal investigator for the Dawn mission, based at the University of California, Los Angeles.

Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena.

The framing cameras were provided by the Max Planck Institute for Solar System Research in Gottingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research in Berlin, and in coordination with the Institute of Computer and Communication Network Engineering in Braunschweig.

The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, was built by Selex ES, and is managed by Italy's National Institute for Astrophysics and Planetology in Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory in New Mexico, and is operated by the Planetary Science Institute of Tucson, Arizona.

Source: Nasa