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A Quantum Bit

Quantum physics began with revolutionary discoveries in the early twentieth century and continues to be central in today’s physics research. Learn about quantum physics, bit by bit. From definitions to the latest research, this is your portal. Subscribe to receive regular emails from the quantum world.

October 17, 2016

Check out the second half of our feature story on Weyl semimetals and Weyl fermions, new materials and particles that have become a major focus for condensed matter researchers around the world. Part two looks at some of the theoretical work going on at JQI and CMTC. If you missed part one, it's not too late to catch up on the series. And if you missed our roundup of the research that led to last week's Nobel Prize in Physicsresearch that is closely related to Weyl materialswe encourage you to take a look.

JQI is also happy to congratulate Karina Jiménez-García on receiving a 2016 L'Oréal-UNESCO For Women in Science fellowship. "This is a recognition that I owe to all those that have guided and inspired me and those who have supported me throughout my professional career, especially my family," Jiménez-García said. We wrote a short story on how she plans to use the fellowship funds. It links to stories about the research she worked on while visiting JQI.

November 18, 2013

Optical cavities can be made by arranging two mirrors facing each other. In this example, light bounces back and forth, forming a standing wave between the mirrors. One of the mirrors is designed to leak out a fraction of the light. Because of the boundaries created by the mirrors, the cavity will only build up light that satisfies a resonance condition--the light's wavelength must be a half-integer multiple of the cavity length. This means that cavities can be used to create narrow frequency sources. Read more to learn more about a cool research result using cavities.

November 14, 2013

Polarization refers to the orientation of traveling waves with respect to a well-defined direction. Polarized sunglasses shield your eyes from light having certain orientations. Projectors that display images having different polarizations are used to generate the 3D effects seen in movies. In quantum information research, two different polarization states of light can make up a photonic qubit.

November 7, 2013

Physicists can engineer quantum magnets using lasers and ion qubits. Ions are charged particles that interact strongly via the Coulomb force, which is an attraction/repulsion that decreases as particles separate. When a handful of positively charged ions are thrown together, they repel each other, and, for an oblong ion trap, form a linear crystal. Each ion has two internal energy states that make up a qubit. Laser beams can manipulate the Coulomb force to create tunable, long range magnetic-like interactions, where each ion qubit represents a tiny magnet. Images of ion traps can be found in our newly launched media galleries.

November 1, 2013

Magneto-optical traps use laser-cooling and magnetic fields to isolate clouds of neutral atoms. Room temperature atoms fly about at many hundreds of meters per second. To capture them in a single location, lasers interact with the atoms, removing energy through the absorption and emission of photons. Rubidium is the most common element used, but the image shown here is of a strontium cloud trapped inside a vacuum chamber.

October 28, 2013

Wave-particle duality is a key part of quantum mechanics. All matter, which as you zoom in appears to be particulate, can also behave like waves. Scientists can directly observe the wave nature of atoms by cooling them down to near-absolute zero temperature. At these temperatures the wavelength of each particle is long and can overlap with other matter waves. Like water waves, atom-wave interference creates ripples and patterns. Click on image to see animated gif in your browser.

October 24, 2013

How do fiber optics work? Light can be confined inside a reflective medium—a stream of water, a thread of glass fiber. The light moves, trapped in these materials via total internal reflection--light “totally” bounces at the surfaces, back and forth. Certain wavelengths of light can travel over vast distances without much loss or signal degradation. Thus information encoded using different attributes of the light (phase, frequency) can be transmitted efficiently. Read more to see how fibers are used in quantum information research.

Image credit: JQI. Figure attributes (color, lighting) altered for artistic purposes with permission of authors.
October 21, 2013

Topological Light: JQI/NIST scientists have observed infrared photons racing around the edge of a room temperature, silicon-on-insulator chip, unobstructed by defects. This novel design assists with the miniaturization of optical communication technology, bringing photons a little closer to their electronic circuit counterparts.