Cloud Computing

Researchers have succeeded in combining the power of quantum computing with the security of quantum cryptography and have shown that perfectly secure cloud computing can be achieved using the principles of quantum mechanics. They have performed an experimental demonstration of quantum computation in which the input, the data processing, and the output remain unknown to the quantum computer.

The international team of scientists will publish the results of the experiment, carried out at the Vienna Center for Quantum Science and Technology (VCQ) at the University of Vienna and the Institute for Quantum Optics and Quantum Information (IQOQI), in the forthcoming issue of Science.

Quantum computers are expected to play an important role in future information processing since they can outperform classical computers at many tasks. Considering the challenges inherent in building quantum devices, it is conceivable that future quantum computing capabilities will exist only in a few specialized facilities around the world -- much like today's supercomputers. Users would then interact with those specialized facilities in order to outsource their quantum computations. The scenario follows the current trend of cloud computing: central remote servers are used to store and process data -- everything is done in the "cloud." The obvious challenge is to make globalized computing safe and ensure that users' data stays private.

The latest research, to appear in Science, reveals that quantum computers can provide an answer to that challenge. "Quantum physics solves one of the key challenges in distributed computing. It can preserve data privacy when users interact with remote computing centers," says Stefanie Barz, lead author of the study. This newly established fundamental advantage of quantum computers enables the delegation of a quantum computation from a user who does not hold any quantum computational power to a quantum server, while guaranteeing that the user's data remain perfectly private. The quantum server performs calculations, but has no means to find out what it is doing -- a functionality not known to be achievable in the classical world.

The scientists in the Vienna research group have demonstrated the concept of "blind quantum computing" in an experiment: they performed the first known quantum computation during which the user's data stayed perfectly encrypted. The experimental demonstration uses photons, or "light particles" to encode the data. Photonic systems are well-suited to the task because quantum computation operations can be performed on them, and they can be transmitted over long distances.

The process works in the following manner. The user prepares qubits -- the fundamental units of quantum computers -- in a state known only to himself and sends these qubits to the quantum computer. The quantum computer entangles the qubits according to a standard scheme. The actual computation is measurement-based: the processing of quantum information is implemented by simple measurements on qubits. The user tailors measurement instructions to the particular state of each qubit and sends them to the quantum server. Finally, the results of the computation are sent back to the user who can interpret and utilize the results of the computation. Even if the quantum computer or an eavesdropper tries to read the qubits, they gain no useful information, without knowing the initial state; they are "blind."

The research at the Vienna Center for Quantum Science and Technology (VCQ) at the University of Vienna and at the Institute for Quantum Optics and Quantum Information (IQOQI) of the Austrian Academy of Sciences was undertaken in collaboration with the scientists who originally invented the protocol, based at the University of Edinburgh, the Institute for Quantum Computing (University of Waterloo), the Centre for Quantum Technologies (National University of Singapore), and University College Dublin
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Batteries

Looking toward improved batteries for charging electric cars and storing energy from renewable but intermittent solar and wind, scientists at Oak Ridge National Laboratory have developed the first high-performance, nanostructured solid electrolyte for more energy-dense lithium ion batteries.

Today's lithium-ion batteries rely on a liquid electrolyte, the material that conducts ions between the negatively charged anode and positive cathode. But liquid electrolytes often entail safety issues because of their flammability, especially as researchers try to pack more energy in a smaller battery volume. Building batteries with a solid electrolyte, as ORNL researchers have demonstrated, could overcome these safety concerns and size constraints.

"To make a safer, lightweight battery, we need the design at the beginning to have safety in mind," said ORNL's Chengdu Liang, who led the newly published study in the Journal of the American Chemical Society. "We started with a conventional material that is highly stable in a battery system -- in particular one that is compatible with a lithium metal anode."

The ability to use pure lithium metal as an anode could ultimately yield batteries five to 10 times more powerful than current versions, which employ carbon based anodes.

"Cycling highly reactive lithium metal in flammable organic electrolytes causes serious safety concerns," Liang said. "A solid electrolyte enables the lithium metal to cycle well, with highly enhanced safety."

The ORNL team developed its solid electrolyte by manipulating a material called lithium thiophosphate so that it could conduct ions 1,000 times faster than its natural bulk form. The researchers used a chemical process called nanostructuring, which alters the structure of the crystals that make up the material.

"Think about it in terms of a big crystal of quartz vs. very fine beach sand," said coauthor Adam Rondinone. "You can have the same total volume of material, but it's broken up into very small particles that are packed together. It's made of the same atoms in roughly the same proportions, but at the nanoscale the structure is different. And now this solid material conducts lithium ions at a much greater rate than the original large crystal."

The researchers are continuing to test lab scale battery cells, and a patent on the team's invention is pending.

"We use a room-temperature, solution-based reaction that we believe can be easily scaled up," Rondinone said. "It's an energy-efficient way to make large amounts of this material."

The study is published as "Anomalous High Ionic Conductivity of Nanoporous β-Li3PS4," and its ORNL coauthors are Zengcai Liu, Wujun Fu, Andrew Payzant, Xiang Yu, Zili Wu, Nancy Dudney, Jim Kiggans, Kunlun Hong, Adam Rondinone and Chengdu Liang. The work was sponsored by the Division of Materials Sciences and Engineering in DOE's Office of Science
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