YSM Issue 90.1

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FOCUS physics IMAGE COURTESY OF HONG TANG ►Professor Hong Tang (right), along with graduate students Chang-Ling Zou (left) and Xu Han (not pictured), developed a piezo-optomechanical resonator that has applications to quantum memory storage. move, the object responds by changing shape physically. In this way, vibrations in physical objects and electrical fields can easily be connected, or, as physicists say, coupled. Piezoelectrics in smartphones often power tiny speakers— they convert electrical signals into sound waves, which arise from physical pulses. The Yale piezo-optomechanical device consists of a pair of tiny resonators: a silicon wafer and a wire loop situated above it. “It is useful to think of a resonator like a tuning fork because it responds most powerfully to a particular resonant frequency,” said Han, an electrical engineering Ph.D candidate who worked on the project. The two ends of the wire loop do not quite connect, so electrical charges tend to bounce back and forth around the circle, which functions as an electrical resonator in the microwave region of the electromagnetic spectrum. The wafer, which is about as thick as five sheets of paper, functions as an acoustic, or mechanical, resonator. This resonator is coated with a thin layer of aluminum nitride, a piezoelectric material, which facilitates the exchange of oscillations—and energy— between mechanical and electrical components. “If you want to transfer information between two systems, it is necessary to have an efficient coupling mechanism,” Han said. The idea of coupling between mechanical and microwave electrical domains is not new; the Yale team’s innovation is achieving stronger coupling on a smaller scale. The key is using resonators with a higher frequency: Whereas other designs have used frequencies on the order of a few million oscillations per second, the Yale design runs at ten billion oscillations per second. As a result, the device is solidly in the so-called strong-coupling regime —meaning that the rate of information transfer is greater than the natural energy dissipation rates of the individual systems—and transmitted signals are clearer and longer-lasting. Yet high frequency comes at the cost of increased construction difficulties. “Since the device is small, it is more susceptible to perturbations in the environment,” Tang said. As a result, the design carefully balances considerations of compactness and robustness. The researchers believe that applications of their breakthrough lie mostly in the far future. “This is fundamental research, so it’s not immediately pertinent to daily life,” Han said. Instead, the piezo-optomechanical resonator’s real value is as a component of more complex systems. Because of the strong coupling achieved, it is well suited for quantum uses where “noise” from ambient heat (analogous to TV static) would otherwise be disruptive. “For high-frequency devices, the temperature requirement is not as low,” Han said. Chang-Ling Zou, a postdoctoral student in Tang’s lab, hopes to develop this strength into a basis for quantum memory storage, which is currently unfeasible at most temperatures. Small vibrating crystals would serve as physical memory, and the resonators would convert between these crystals and the computational part of the computer, which would likely operate in the microwave domain. The Yale team is also looking to incorporate visible light into their design. “The next step is integrating an optical resonator and using the acoustic resonator as an intermediary between microwave and optics,” Han said. Accomplishing this feat could improve computer signal processing, radio receiving efficiency, and information transmission across long distances via optical fiber cables. Given its versatility, the piezo-optomechanical resonator may find its way into all kinds of applications. From analyzing the stock market to sending trans-Atlantic messages, you can expect to hear more about this small device in big-time situations. ABOUT THE AUTHOR NOAH KRAVITZ NOAH KRAVITZ is a freshman in Calhoun College. He is interested in studying math, music, physics and philosophy. THE AUTHOR WOULD LIKE TO THANK Xu Han, Chang-Ling Zou, and Professor Hong Tang for explaining their research. FURTHER READING Li, Mo, W.H.P. Pernice, and H.X. Tang. “Ultrahigh-Frequency Nano- Optomechanical Resonators in Slot Waveguide Ring Cavities.” Applied Physics Letters 07 (2010). 24 Yale Scientific Magazine December 2016 www.yalescientific.org
evolutionary biology FEATURE A WORLD OF WONDER Opening the David Friend Hall at the Peabody Museum ►BY CHUNYANG DING Nearly every observed galaxy has a giant black hole at its center. Step into the Peabody’s new David Friend Hall and it might take a minute for your eyes to adjust to the darkness—and then another hour for your mind to adjust to the dazzling marvels that surround you. From the 2000-pound, single-quartz crystal from Namibia to the 30-million-year-old sandstone concretion with smooth undulating curves, each object in the hall aims to wows visitors. Curators carefully chose every detail—from the lighting to the case design—to showcase the world-class treasures here in New Haven, Connecticut. Dramatic lighting highlights specimens with dazzling clarity and draws attention to the kaleidoscope of colors filling the hall. This focus on showmanship was well developed; David Friend (YC ’69), who donated three million dollars for the exhibit, hoped to fill people with a sense of wonder. “The function of a museum is not so much to teach but to inspire a desire to learn,” Friend said shortly before he cut the ribbon to officially open the exhibit. It is fitting for Yale to host this transformative mineral exhibit, since modern mineralogy originated here. Just as Carl Linneaus brought order to the natural world by classifying plants and animals, Yale professor James Dwight Dana brought order to the world of rocks and minerals with a classification scheme that is still used today. Geology has always been strong at Yale; Benjamin Silliman, Yale’s first science professor, started the American Journal of Science in 1818. Not only is the AJS IMAGE COURTESY OF MICHAEL MARSLAND ►Prominent members of the Yale and New Haven communities attended the ribbon cutting ceremony with David Friend (YC ’69). The opening speeches set the tone for an exhibit that would wow visitors. the oldest scientific journal in the United States, it is one of the most influential journals in the fields of geology and mineralogy. The Peabody Museum continues to challenge the expectations for natural history museums with the David Friend Hall. Rather than bombard visitors with text, the exhibit isolates the singular beauty of sparkling minerals. Educational materials for the displays are captured by a smartphone application, where visitors can access and browse background information. In addition, the gallery will feature rotating exhibits: many gems are on loan from private collectors, so new treasures can be featured in the future. Although art galleries often feature loaned art, the David Friend Hall is one of the first natural history exhibits to do the same. And the treasures are dazzling, indeed. Beside the 2000-pound quartz stands a giant geode from Uruguay, completely encrusted by deep purple amethyst shards. Nearby, a white-board-sized fossil of a fan-like frond flanked by ancient fish demands your attention. The crystals, ranging from a five-by-four-foot fluorite from China to miniature “thumbnail” specimens in a display case, vary in size, shape, and geographic origin. “If you go around and look at every single crystal, they’re from all over the world,” said Dave Skelly, the Director of the Peabody Museum. Stefan Nicolescu, head of the Peabody’s minerology collections, guided the selection of minerals, consulting private collections throughout the region and selecting specimens for their wow factor. “The interest is to stir curiosity and to make people want to know more about these things,” said Nicolescu. The recent ribbon cutting ceremony thoroughly explored this theme of curiosity and inspiration: “The goal is to capture people’s imagination, particularly the imaginations of budding young scientists, to get them fascinated by the natural world,” said Jay Ague, chair of Yale’s Geology and Geophysics department. They hope to reach far beyond New Haven. Since its conception 150 years ago, the Peabody Museum has served as the archetype for many natural history museums. The curators of the David Friend Hall hope that their setup will also set an example that diffuses globally. For New Haven residents and Yale University students, the hall breathes new life into an already brilliant collection of natural history. “I think this exhibit will certainly bring more students up [to the Peabody],” said Dean Jonathan Holloway. The brilliant jewels may prompt curiosity for understanding our world. www.yalescientific.org December 2016 Yale Scientific Magazine 25
Page 1 and 2: Yale Scientific Established in 1894
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Page 7 and 8: in brief NEWS The Miller laboratory
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Page 11 and 12: medicine NEWS THE FLU SEASON CRAVIN
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Page 37 and 38: ALUMNI PROFILE DR. RALPH GRECO, M.D
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YSM Issue 90.1

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