David Kirkpatrick

October 25, 2010

One terabit optical ethernet

Coming to a point-of-presence near you in the near future.

From the link:

Researchers with the Terabit Optical Ethernet Center (TOEC) at the University of California, Santa Barbara (UCSB) are aiming for 1 Terabit Ethernet over optical fiber — 1 trillion bits per second — by 2015 and 100 Terabit Ethernet by 2020. Partnering with TOEC as founding industry affiliates are Google Inc., Verizon, Intel, Agilent Technologiesand Rockwell Collins Inc.

Ethernet is constantly evolving, but soon — in as little as five years, according to some estimates — it won’t be able to keep up with the speed and bandwidth required for applications like video and cloud computing, and distributed data storage. “Based on current traffic growth, it’s clear that 1 Terabit per second trunks will be needed in the near future,” says Stuart Elby, Vice President of Network Architecture for Verizon.

Current Ethernet technologies can’t be pushed much past 100 Gigabits per second — the speed that’s beginning to be implemented now — mainly because of the amount of power needed to run and cool the required systems, says Daniel Blumenthal, Professor of Electrical and Computer Engineering at UCSB and Director of TOEC. Large data centers can consume as much power as a small city. New generations of Ethernet need to be much more energy-efficient and cost-effective, or the power problem will limit Ethernet development, crippling the growth of key U.S. industries and technologies.

 

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July 8, 2010

Latest on quantum computing

There’s been a mini-flurry of quantum computing news of late, and here’s the latest. Even though quantum computing news is both fun and interesting it’s best to keep in mind we are nowhere close to actually building anything the average person would consider a quantum computer. The payoff for all this research and development, however, is worth the effort and certainly worth keeping track of.

From the second link:

One of the more interesting runners in the race to build scalable quantum computers is the idea of using point-like defects in a diamond lattice that have been filled with a nitrogen atom. The nitrogen interloper provides an extra electron which can be used to generate photons or to store quantum information.

The big advantage of these so-called nitrogen vacancies is that they’re easy to see (because they can be made to emit photons) which means they can be relatively easily addressed. They are also well isolated from many types of environmental interference and so can store qubits for relatively long periods of up to several hundred microseconds.

But the problem is how to make them en masse. Until now, the fastest way was to fire nitrogen atoms one by one through an aperture into a thin layer of diamond. That makes for slow going if you need hundreds of thousands of them in a single layer.

Now David Toyli at the University of California, Santa Barbara, and few buddies have demonstrated a much faster technique. Their approach is to cover the diamond with a thin layer of resist, through which they then blast an array of holes using electron beam lithography.

February 7, 2010

Another step closer to quantum computers

Here’s the release from Friday:

Princeton scientist makes a leap in quantum computing

A major hurdle in the ambitious quest to design and construct a radically new kind of quantum computer has been finding a way to manipulate the single electrons that very likely will constitute the new machines’ processing components or “qubits.”

Princeton University’s Jason Petta has discovered how to do just that — demonstrating a method that alters the properties of a lone electron without disturbing the trillions of electrons in its immediate surroundings. The feat is essential to the development of future varieties of superfast computers with near-limitless capacities for data.

Petta, an assistant professor of physics, has fashioned a new method of trapping one or two electrons in microscopic corrals created by applying voltages to minuscule electrodes. Writing in the Feb. 5 edition of Science, he describes how electrons trapped in these corrals form “spin qubits,” quantum versions of classic computer information units known as bits. Other authors on the paper include Art Gossard and Hong Lu at the University of California-Santa Barbara.

Previous experiments used a technique in which electrons in a sample were exposed to microwave radiation. However, because it affected all the electrons uniformly, the technique could not be used to manipulate single electrons in spin qubits. It also was slow. Petta’s method not only achieves control of single electrons, but it does so extremely rapidly — in one-billionth of a second.

“If you can take a small enough object like a single electron and isolate it well enough from external perturbations, then it will behave quantum mechanically for a long period of time,” said Petta. “All we want is for the electron to just sit there and do what we tell it to do. But the outside world is sort of poking at it, and that process of the outside world poking at it causes it to lose its quantum mechanical nature.”

When the electrons in Petta’s experiment are in what he calls their quantum state, they are “coherent,” following rules that are radically different from the world seen by the naked eye. Living for fractions of a second in the realm of quantum physics before they are rattled by external forces, the electrons obey a unique set of physical laws that govern the behavior of ultra-small objects.

Scientists like Petta are working in a field known as quantum control where they are learning how to manipulate materials under the influence of quantum mechanics so they can exploit those properties to power advanced technologies like quantum computing. Quantum computers will be designed to take advantage of these characteristics to enrich their capacities in many ways.

In addition to electrical charge, electrons possess rotational properties. In the quantum world, objects can turn in ways that are at odds with common experience. The Austrian theoretical physicist Wolfgang Pauli, who won the Nobel Prize in Physics in 1945, proposed that an electron in a quantum state can assume one of two states — “spin-up” or “spin-down.” It can be imagined as behaving like a tiny bar magnet with spin-up corresponding to the north pole pointing up and spin-down corresponding to the north pole pointing down.

An electron in a quantum state can simultaneously be partially in the spin-up state and partially in the spin-down state or anywhere in between, a quantum mechanical property called “superposition of states.” A qubit based on the spin of an electron could have nearly limitless potential because it can be neither strictly on nor strictly off.

New designs could take advantage of a rich set of possibilities offered by harnessing this property to enhance computing power. In the past decade, theorists and mathematicians have designed algorithms that exploit this mysterious superposition to perform intricate calculations at speeds unmatched by supercomputers today.

Petta’s work is using electron spin to advantage.

“In the quest to build a quantum computer with electron spin qubits, nuclear spins are typically a nuisance,” said Guido Burkard, a theoretical physicist at the University of Konstanz in Germany. “Petta and coworkers demonstrate a new method that utilizes the nuclear spins for performing fast quantum operations. For solid-state quantum computing, their result is a big step forward.”

Petta’s spin qubits, which he envisions as the core of future quantum logic elements, are cooled to temperatures near absolute zero and trapped in two tiny corrals known as quantum wells on the surface of a high-purity, gallium arsenide chip. The depth of each well is controlled by varying the voltage on tiny electrodes or gates. Like a juggler tossing two balls between his hands, Petta can move the electrons from one well to the other by selectively toggling the gate voltages.

Prior to this experiment, it was not clear how experimenters could manipulate the spin of one electron without disturbing the spin of another in a closely packed space, according to Phuan Ong, the Eugene Higgins Professor of Physics at Princeton and director of the Princeton Center for Complex Materials.

Other experts agree.

“They have managed to create a very exotic transient condition, in which the spin state of a pair of electrons is in that moment entangled with an almost macroscopic degree of freedom,” said David DiVencenzo, a research staff member at the IBM Thomas J. Watson Research Center in Yorktown Heights, N.Y.

Petta’s research also is part of the fledgling field of “spintronics” in which scientists are studying how to use an electron’s spin to create new types of electronic devices. Most electrical devices today operate on the basis of another key property of the electron — its charge.

There are many more challenges to face, Petta said.

“Our approach is really to look at the building blocks of the system, to think deeply about what the limitations are and what we can do to overcome them,” Petta said. “But we are still at the level of just manipulating one or two quantum bits, and you really need hundreds to do something useful.”

As excited as he is about present progress, long-term applications are still years away. “It’s a one-day-at-a-time approach,” Petta said.

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