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Experiments at UCSB push quantum mechanics to higher levels
August 12, 2009(Santa Barbara, Calif.) -- Scientists at UC Santa Barbara have devised a new type of superconducting circuit that behaves quantum mechanically -- but has up to five levels of energy instead of the usual two. The findings are published in the August 7 issue of Science.
These circuits act like artificial atoms in that they can only gain or lose energy in packets, or quanta, by jumping between discrete energy levels. "In our previous work, we focused on systems with just two energy levels, 'qubits,' because they are the quantum analog of 'bits,' which have two states, on and off," said Matthew Neeley, first author and a graduate student at UCSB.
He explained that in this work they operated a quantum circuit as a more complicated artificial atom with up to five energy levels. The generic term for such a system is "qudit," where 'd' refers to the number of energy levels -- in this case, 'd' equals five.
"This is the quantum analog of a switch that has several allowed positions, rather than just two," said Neeley. "Because it has more energy levels, the physics of a qudit is richer than for just a single qubit. This allows us to explore certain aspects of quantum mechanics that go beyond what can be observed with a qubit."
Just as bits are used as the fundamental building blocks of computers, qubits could one day be used as building blocks of a quantum computer, a device that exploits the laws of quantum mechanics to perform certain computations faster than can be done with classical bits alone. "Qudits can be used in quantum computers as well, and there are even cases where qudits could be used to speed up certain operations with a quantum computer," said Neeley. "Most research to date has focused on qubit systems, but we hope our experimental demonstration will motivate more effort on qudits, as an addition to the quantum information processing toolbox."
University of California - Santa Barbara
"This is the quantum analog of a switch that has several allowed positions, rather than just two," said Neeley. "Because it has more energy levels, the physics of a qudit is richer than for just a single qubit. This allows us to explore certain aspects of quantum mechanics that go beyond what can be observed with a qubit."
Just as bits are used as the fundamental building blocks of computers, qubits could one day be used as building blocks of a quantum computer, a device that exploits the laws of quantum mechanics to perform certain computations faster than can be done with classical bits alone. "Qudits can be used in quantum computers as well, and there are even cases where qudits could be used to speed up certain operations with a quantum computer," said Neeley. "Most research to date has focused on qubit systems, but we hope our experimental demonstration will motivate more effort on qudits, as an addition to the quantum information processing toolbox."
University of California - Santa Barbara
Quantum Mechanics Current Events and Quantum Mechanics News RSSNIST demonstrates 'universal' programmable quantum processor
Physicists at the National Institute of Standards and Technology (NIST) have demonstrated the first "universal" programmable quantum information processor able to run any program allowed by quantum mechanics-the rules governing the submicroscopic world-using two quantum bits (qubits) of information.
First Bose-Einstein condensation of strontium
In an international first, scientists from the Institute of Quantum Optics and Quantum Information (IQOQI) produced a Bose-Einstein condensate of the alkaline-earth element strontium, thus narrowly winning an international competition between many first-rate scientific groups
Quantum gas microscope offers glimpse of quirky ultracold atoms
Physicists at Harvard University have created a quantum gas microscope that can be used to observe single atoms at temperatures so low the particles follow the rules of quantum mechanics, behaving in bizarre ways.
Quantum computer chips now 1 step closer to reality
In the quest for smaller, faster computer chips, researchers are increasingly turning to quantum mechanics -- the exotic physics of the small. The problem: the manufacturing techniques required to make quantum devices have been equally exotic. That is, until now.
Field experiment on a robust hierarchical metropolitan quantum cryptography network
Key Laboratory of Quantum Information (CAS), University of Science and Technology of China has recently demonstrated a metropolitan Quantum Cryptography Network (QCN) for Government Administration in Wuhu, China. Because of its scientific significance and social impact, the project is reported in Volume 54, Issue 17 (September, 2009) of the Chinese Science Bulletin authored by Fang-xing Xu et al.
UA scientists discover quantum fingerprints of chaos
Chaotic behavior is the rule, not the exception, in the world we experience through our senses, the world governed by the laws of classical physics.
Building a better qubit
Exploiting quantum mechanics for transmitting information is a tantalizing possibility because it promises secure, high speed communications.
Physicists at UC Santa Barbara make discovery in quantum mechanics
Physicists at UC Santa Barbara have made an important advance in quantum mechanics using a superconducting electrical circuit. The finding is reported in this week's issue of the journal Nature.
A tiny, tunable well of light, and a string theorist's toolbox
Photonics, the science of using photons to carry information, promises to continue improving a wide variety of technologies, from computing to high-speed communication.
Atoms don't dance the 'bose nova'
Hanns-Christoph Naegerl's research group has investigated how ultracold quantum gases behave in lower spatial dimensions. They successfully realized an exotic state, where, due to the laws of quantum mechanics, atoms align along a one-dimensional structure.
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