QEG - Who We Work For
    Video of the week: Printable magnets

    The following two stories demonstrate potential energy saving in digital technologies, Why it is important that we seek new and environmentally friendly energy sources, it is also equally important to find new inefficiencies.  Decreasing power required or increasing speed can have the desired effect.

    Experiments show magnetic chips could dramatically increase computing’s energy efficiency

    Magnetic microscope image of three nanomagnetic computer bits. Each bit is a tiny bar magnet only 90 nanometers long. The microscope shows a bright spot at the “North” end and a dark spot at the “South” end of the magnet. The “H” arrow shows the direction of magnetic field applied to switch the direction of the magnets. (Image by Jeongmin Hong and Jeffrey Bokor)

    In a breakthrough for energy-efficient computing, engineers at the University of California, Berkeley, have shown for the first time that magnetic chips can operate with the lowest fundamental level of energy dissipation possible under the laws of thermodynamics.

    “We wanted to know how small we could shrink the amount of energy needed for computing,” said senior author Jeffrey Bokor, a UC Berkeley professor of electrical engineering and computer sciences and a faculty scientist at the Lawrence Berkeley National Laboratory. “The biggest challenge in designing computers and, in fact, all our electronics today is reducing their energy consumption.”

    Lowering energy use is a relatively recent shift in focus in chip manufacturing after decades of emphasis on packing greater numbers of increasingly tiny and faster transistors onto chips.

    “Making transistors go faster was requiring too much energy,” said Bokor, who is also the deputy director the Center for Energy Efficient Electronics Science, a Science and Technology Center at UC Berkeley funded by the National Science Foundation. “The chips were getting so hot they’d just melt.”

    Magnetic computing

    Magnetic computing emerged as a promising candidate because the magnetic bits can be differentiated by direction, and it takes just as much energy to get the magnet to point left as it does to point right.

    “These are two equal energy states, so we don’t throw energy away creating a high and low energy,” said Bokor.

    Bokor teamed up with UC Berkeley postdoctoral researcher Jeongmin Hong, UC Berkeley graduate student Brian Lambson and Scott Dhuey at the Berkeley Lab’s Molecular Foundry, where the nanomagnets used in the study were fabricated. They experimentally tested and confirmed the Landauer limit, named after IBM Research Lab’s Rolf Landauer, who in 1961 found that in any computer, each single bit operation must expend an absolute minimum amount of energy.

    Landauer’s discovery is based on the second law of thermodynamics, which states that as any physical system is transformed, going from a state of higher concentration to lower concentration, it gets increasingly disordered. That loss of order is called entropy, and it comes off as waste heat.

    Landauer developed a formula to calculate this lowest limit of energy required for a computer operation. The result depends on the temperature of the computer; at room temperature, the limit amounts to about 3 zeptojoules, or one-hundredth the energy given up by a single atom when it emits one photon of light.

    The UC Berkeley team used an innovative technique to measure the tiny amount of energy dissipation that resulted when they flipped a nanomagnetic bit. The researchers used a laser probe to carefully follow the direction that the magnet was pointing as an external magnetic field was used to rotate the magnet from “up” to “down” or vice versa.

    They determined that it only took 15 millielectron volts of energy – the equivalent of 3 zeptojoules – to flip a magnetic bit at room temperature, effectively demonstrating the Landauer limit.

    Dramatic reductions in power consumption are possible — down to as little as one-millionth the amount of energy per operation used by transistors in modern computers.

    Links

    http://news.berkeley.edu/2016/03/11/magnetic-chips-low-power-computing/

    http://spectrum.ieee.org/tech-talk/semiconductors/devices/zeptojoule-nanomagnetic-switch-supports-fundamental-limit-of-computing

    http://phys.org/news/2016-03-magnetic-chips-energy-efficiency.html

    Light helps the transistor laser switch faster

    A new study by University of Illinois engineers found that in the transistor laser, a device for next-generation high-speed computing, the light and electrons spur one another on to faster switching speeds than any devices available.

     

    Junyi Qiu, Curtis Wang and Milton Feng) for Intra Cavity Photon Assisted Tunneling (ICpaT)

    Graduate students Junyi Wu and Curtis Wang and professor Milton Feng found that light stimulates switching speed in the transistor laser, a device they hope will usher in the next generation of high-speed data transmission. Photo by L. Brian Stauffer

    100 Times Faster

    As big data become bigger and cloud computing becomes more commonplace, the infrastructure for transferring the ever-increasing amounts of data needs to speed up, Feng said. Traditional technologies used for fiber optic cables and high-speed data transmission, such as diode lasers, are reaching the upper end of their switching speeds, Feng said.

    “You can compute all you want in a data center. However, you need to take that data in and out of the system for the user to use,” Feng said. “You need to transfer the information for it to be useful, and that goes through these fiber optic interconnects. But there is a fundamental switching limitation of the diode laser used. This technology, the transistor laser, is the next-generation technology, and could be a hundred times faster.”

    Diode lasers have two ports: an electrical input and a light output. By contrast, the transistor laser has three ports: an electrical input, and both electrical and light outputs.

    The three-port design allows the researchers to harness the intricate physics between electrons and light. For example, the fastest way for current to switch in a semiconductor material is for the electrons to jump between bands in the material in a process called tunneling. Light photons help shuttle the electrons across, a process called photon-assisted tunneling, making the device much faster.

    “The collector can absorb the photon from the laser for very quick tunneling, so that becomes a direct-voltage-modulation scheme, much faster than using current modulation,” Feng said. “We also proved that the stimulated photon-assisted tunneling process is much faster than regular photon-assisted tunneling. Previous engineers could not find this because they did not have the transistor laser. With just a diode laser, you cannot discover this.

    Links

    https://news.illinois.edu/blog/view/6367/336751
    http://www.eurekalert.org/pub_releases/2016-03/uoia-lht030916.php
    http://www.sciencenewsline.com/news/2016030918520079.html

    A new study by University of Illinois engineers found that in the transistor laser, a device for next-generation high-speed computing, the light and electrons spur one another on to faster switching speeds than any devices available.

    This technology, the transistor laser, is the next-generation technology, and could be a hundred times faster.”

    “The collector can absorb the photon from the laser for very quick tunneling, so that becomes a direct-voltage-modulation scheme, much faster than using current modulation,” Feng said. “We also proved that the stimulated photon-assisted tunneling process is much faster than regular photon-assisted tunneling. Previous engineers could not find this because they did not have the transistor laser. With just a diode laser, you cannot discover this.

    “This is not only proving the scientific point, but it’s very useful for high-speed device modulation. We can directly modulate the laser into the femtosecond range. That allows a tremendous amount of energy-efficient data transfer,” Feng said.

    QEG - Who We Work For
    Video of the week: Printable magnets