Global symmetry not required for fast quantum search
A quantum particle can search for an item in an unsorted "database" by jumping from one item to another in superposition, and it does so faster than a classical computer ever could.
In a complete graph (left) every node is connected to every other. For other well studied graphs, the Paley graph in the center and the Latin square graph on the right, that is not true. A quantum particle could hop directly to the target position, in red, only from connected nodes, marked in blue.
Credit: Tom Wong, UC San Diego
This assertion assumes, however, that the particle can directly hop from any item to any other. Any restriction on which items the particle can directly hop to could slow down the search.
"Intuition says that a symmetric database allows the particle to hop freely enough to retain the quantum speedup, but our research has shown this intuition to be false," says Tom Wong, a physicist at the University of California, San Diego.
In a paper accepted for publication by Physical Review Letters, the researchers used a technique familiar to physicists called "degenerate perturbation theory" in a novel way to prove that global symmetry is not required for a sped up search.
Information scientists represent the database to be searched as a graph. In globally symmetric graphs, the nodes can be swapped with each other such that the connections between them are preserved. "Strongly regular graphs" don't share this property, but this analysis shows they also support a fast search through local symmetries.
Their finding extends the use of this theory to the field of quantum information science and expands the kinds of data structures on which quantum computing outperforms classical computing.
Jonatan Janmark, KTH Royal Institute of Technology in Stockholm, Sweden and UC San Diego's Department of Mathematics and David Meyer, professor of mathematics at UC San Diego co-authored the work.
The Defense Advanced Research Projects Agency partially supported this work as part of its Quantum Entanglement Science and Technology program. Additional funding came from the Air Force Office of Scientific Research as part of the Transformational Computing in Aerospace Science and Engineering Initiative, and the Achievement Awards for College Scientists Foundation.
Tom Wong | Eurek Alert!
Hubble discovers mysterious black hole disc
12.07.2019 | ESA/Hubble Information Centre
What happens when you explode a chemical bond?
12.07.2019 | University of California - Berkeley
For some phenomena in quantum many-body physics several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University in the United States has now successfully deployed artificial neural networks for image analysis of quantum systems.
Is that a dog or a cat? Such a classification is a prime example of machine learning: artificial neural networks can be trained to analyze images by looking...
An international research group led by scientists from the University of Bayreuth has produced a previously unknown material: Rhenium nitride pernitride. Thanks to combining properties that were previously considered incompatible, it looks set to become highly attractive for technological applications. Indeed, it is a super-hard metallic conductor that can withstand extremely high pressures like a diamond. A process now developed in Bayreuth opens up the possibility of producing rhenium nitride pernitride and other technologically interesting materials in sufficiently large quantity for their properties characterisation. The new findings are presented in "Nature Communications".
The possibility of finding a compound that was metallically conductive, super-hard, and ultra-incompressible was long considered unlikely in science. It was...
An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.
Fuel cells may well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus...
The fly agaric with its red hat is perhaps the most evocative of the diverse and variously colored mushroom species. Hitherto, the purpose of these colors was...
Physicists at the Max Planck Institute for Nuclear Physics in Heidelberg report the first result of the new Alphatrap experiment. They measured the bound-electron g-factor of highly charged (boron-like) argon ions with unprecedented precision of 9 digits. In comparison with a new highly accurate quantum electrodynamic calculation they found an excellent agreement on a level of 7 digits. This paves the way for sensitive tests of QED in strong fields like precision measurements of the fine structure constant α as well as the detection of possible signatures of new physics. [Physical Review Letters, 27 June 2019]
Quantum electrodynamics (QED) describes the interaction of charged particles with electromagnetic fields and is the most precisely tested physical theory. It...
24.06.2019 | Event News
29.04.2019 | Event News
17.04.2019 | Event News
15.07.2019 | Life Sciences
15.07.2019 | Power and Electrical Engineering
15.07.2019 | Life Sciences