Items tagged with "quantum computing"
Symmetry permeates nature, from the radial symmetry of flowers to the left-right symmetry of the human body. As such, it provides a natural way of classifying objects by grouping those that share the same symmetry. This is particularly useful for describing transitions between phases of matter. For example, liquid and gas phases have translational symmetry, meaning the arrangement of molecules doesn’t change regardless of the direction from which they are observed.
If you’re designing a new computer, you want it to solve problems as fast as possible. Just how fast is possible is an open question when it comes to quantum computers, but JQI physicists have narrowed the theoretical limits for where that “speed limit” is. The work implies that quantum processors will work more slowly than some research has suggested.
JQI researchers, under the direction of Christopher Monroe have demonstrated modular entanglement between two atomic systems, separated by one meter. Here, photons are the long distance information carriers entangling multiple qubit modules.
In quantum mechanics, interactions between particles can give rise to entanglement, which is a strange type of connection that could never be described by a non-quantum, classical theory. These connections, called quantum correlations, are present in entangled systems even if the objects are not physically linked (with wires, for example). Entanglement is at the heart of what distinguishes purely quantum systems from classical ones; it is why they are potentially useful, but it sometimes makes them very difficult to understand.
Physicists led by ion-trapper Christopher Monroe at the JQI have proposed a modular quantum computer architecture that promises scalability to much larger numbers of qubits. The components of this architecture have individually been tested and are available, making it a promising approach. In the paper, the authors present expected performance and scaling calculations, demonstrating that their architecture is not only viable, but in some ways, preferable when compared to related schemes.
Quantum dots (QD) can be made from tiny crystals of semiconductor material, around 10 nanometers in size. The electron hole pairs in this structure are confined, resulting in a quantization of energy levels analogous to those of an atom – hence quantum dots are often dubbed ‘artificial atoms.’ Like an atom, a QD’s energy levels can be manipulated using lasers and magnetic fields. The fluorescing wavelengths can be tuned by altering the crystal size. Semiconductor quantum dots are attractive for quantum information processing because the technology for integration with modern electronics already exists. Read more to learn more about these artificial atoms.
This week’s issue of Science Magazine features new results from the research group of Christopher Monroe at the JQI, where they explored how to frustrate a quantum magnet comprised of sixteen atomic ions – to date the largest ensemble of qubits to perform a simulation of quantum matter.
All computers, even the future quantum versions, use logic operations or “gates,” which are the fundamental building blocks of computational processes. JQI scientists, led by Professor Edo Waks, have performed an ultrafast logic gate on a photon, using a semiconductor quantum dot.
Recently Science Magazine invited JQI fellow Chris Monroe and Duke Professor Jungsang Kim to speculate on ion trap technology as a scalable option for quantum information processing. The article is highlighted on the cover of this week’s (March 8, 2013) issue, which is dedicated to quantum information. The cover portrays a photograph of a surface trap that was fabricated by Sandia National Labs and used to trap ions at JQI and Duke, among other laboratories.