{"id":4166,"date":"2015-05-15T06:12:23","date_gmt":"2015-05-15T06:12:23","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=4166"},"modified":"2015-05-15T06:14:18","modified_gmt":"2015-05-15T06:14:18","slug":"researchers-build-new-fermion-microscope","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/researchers-build-new-fermion-microscope\/","title":{"rendered":"Researchers build new fermion microscope"},"content":{"rendered":"

Instrument freezes and images 1,000 individual fermionic atoms at once.<\/strong><\/em><\/p>\n

\"Graduate<\/a>
Graduate student Lawrence Cheuk adjusts the optics setup for laser cooling of sodium atoms.
Photo: Jose-Luis Olivares\/MIT<\/figcaption><\/figure>\n

CAMBRIDGE, Mass. —\u00a0Fermions are the building blocks of matter, interacting in a multitude of permutations to give rise to the elements of the periodic table. Without fermions, the physical world would not exist.<\/p>\n

Examples of fermions are electrons, protons, neutrons, quarks, and atoms consisting of an odd number of these elementary particles. Because of their fermionic nature, electrons and nuclear matter are difficult to understand theoretically, so researchers are trying to use ultracold gases of fermionic atoms as stand-ins for other fermions.<\/p>\n

\"The<\/a>
The Fermi gas microscope group: (from left) graduate students Katherine Lawrence and Melih Okan, postdoc Thomas Lompe, graduate student Matt Nichols, Professor Martin Zwierlein, and graduate student Lawrence Cheuk.
Photo: Jose-Luis Olivares\/MIT<\/figcaption><\/figure>\n

But atoms are extremely sensitive to light: When a single photon hits an atom, it can knock the particle out of place \u2014 an effect that has made imaging individual fermionic atoms devilishly hard.<\/p>\n

Now a team of MIT physicists has built a microscope that is able to see up to 1,000 individual fermionic atoms. The researchers devised a laser-based technique to trap and freeze fermions in place, and image the particles simultaneously.<\/p>\n

The new imaging technique uses two laser beams trained on a cloud of fermionic atoms in an optical lattice. The two beams, each of a different wavelength, cool the cloud, causing individual fermions to drop down an energy level, eventually bringing them to their lowest energy states \u2014 cool and stable enough to stay in place. At the same time, each fermion releases light, which is captured by the microscope and used to image the fermion\u2019s exact position in the lattice \u2014 to an accuracy better than the wavelength of light.<\/p>\n

With the new technique, the researchers are able to cool and image over 95 percent of the fermionic atoms making up a cloud of potassium gas. Martin Zwierlein, a professor of physics at MIT, says an intriguing result from the technique appears to be that it can keep fermions cold even after imaging.<\/p>\n

\u201cThat means I know where they are, and I can maybe move them around with a little tweezer to any location, and arrange them in any pattern I\u2019d like,\u201d Zwierlein says.<\/p>\n

Zwierlein and his colleagues, including first author and graduate student Lawrence Cheuk, have published their results today in the journal\u00a0Physical Review Letters.<\/em><\/p>\n

Seeing fermions from bosons<\/strong><\/p>\n

For the past two decades, experimental physicists have studied ultracold atomic gases of the two classes of particles: fermions and bosons \u2014 particles such as photons that, unlike fermions, can occupy the same quantum state in limitless numbers. In 2009, physicist Marcus Greiner at Harvard University devised a microscope that successfully imaged individual bosons in a tightly spaced optical lattice. This milestone was followed, in 2010, by a second boson microscope, developed by Immanuel Bloch\u2019s group at the Max Planck Institute of Quantum Optics.<\/p>\n

These microscopes revealed, in unprecedented detail, the behavior of bosons under strong interactions. However, no one had yet developed a comparable microscope for fermionic atoms.<\/p>\n

\u201cWe wanted to do what these groups had done for bosons, but for fermions,\u201d Zwierlein says. \u201cAnd it turned out it was much harder for fermions, because the atoms we use are not so easily cooled. So we had to find a new way to cool them while looking at them.\u201d<\/p>\n

Techniques to cool atoms ever closer to absolute zero have been devised in recent decades. Carl Wieman, Eric Cornell, and MIT\u2019s Wolfgang Ketterle were able to achieve Bose-Einstein condensation in 1995, a milestone for which they were awarded the 2001 Nobel Prize in physics. Other techniques include a process using lasers to cool atoms from 300 degrees Celsius to a few ten-thousandths of a degree above absolute zero.<\/p>\n

A clever cooling technique<\/strong><\/p>\n

And yet, to see individual fermionic atoms, the particles need to be cooled further still. To do this, Zwierlein\u2019s group created an optical lattice using laser beams, forming a structure resembling an egg carton, each well of which could potentially trap a single fermion. Through various stages of laser cooling, magnetic trapping, and further evaporative cooling of the gas, the atoms were prepared at temperatures just above absolute zero \u2014 cold enough for individual fermions to settle onto the underlying optical lattice. The team placed the lattice a mere 7 microns from an imaging lens, through which they hoped to see individual fermions.<\/p>\n

However, seeing fermions requires shining light on them, causing a photon to essentially knock a fermionic atom out of its well, and potentially out of the system entirely.<\/p>\n

\u201cWe needed a clever technique to keep the atoms cool while looking at them,\u201d Zwierlein says.<\/p>\n

His team decided to use a two-laser approach to further cool the atoms; the technique manipulates an atom\u2019s particular energy level, or vibrational energy. Each atom occupies a certain energy state \u2014 the higher that state, the more active the particle is. The team shone two laser beams of differing frequencies at the lattice. The difference in frequencies corresponded to the energy between a fermion\u2019s energy levels. As a result, when both beams were directed at a fermion, the particle would absorb the smaller frequency, and emit a photon from the larger-frequency beam, in turn dropping one energy level to a cooler, more inert state. The lens above the lattice collects the emitted photon, recording its precise position, and that of the fermion.<\/p>\n

Zwierlein says such high-resolution imaging of more than 1,000 fermionic atoms simultaneously would enhance our understanding of the behavior of other fermions in nature \u2014 particularly the behavior of electrons. This knowledge may one day advance our understanding of high-temperature superconductors, which enable lossless energy transport, as well as quantum systems such as solid-state systems or nuclear matter.<\/p>\n

\u201cThe Fermi gas microscope, together with the ability to position atoms at will, might be an important step toward the realization of a quantum computer based on fermions,\u201d Zwierlein says. \u201cOne would thus harness the power of the very same intricate quantum rules that so far hamper our understanding of electronic systems.\u201d<\/p>\n

This research was funded in part by the National Science Foundation, the Air Force Office of Scientific Research, the Office of Naval Research, the Army Research Office, and the David and Lucile Packard Foundation.<\/p>\n","protected":false},"excerpt":{"rendered":"

Instrument freezes and images 1,000 individual fermionic atoms at once. CAMBRIDGE, Mass. —\u00a0Fermions are the building blocks of matter, interacting in a multitude of permutations to give rise to the elements of the periodic table. Without fermions, the physical world would not exist. Examples of fermions are electrons, protons, neutrons, quarks, and atoms consisting of […]<\/p>\n","protected":false},"author":2,"featured_media":4167,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-4166","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-news"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/05\/MIT-Fermion-1.jpg",150,100,false]},"author_info":{"info":["RevoScience"]},"category_info":"News<\/a>","tag_info":"News","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4166","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=4166"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4166\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/4167"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=4166"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=4166"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=4166"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}