February 15, 2016.
In the field of atomic, molecular and optical (AMO) science, lasers are used as a tool for regulatively manipulating the quantum states and for coherently controlling the interactions among quantum objects. Such ambition to conduct favorable outcomes in the quantum world and exploitation of quantum phenomena, especially in quantum information science, would not be possible without laser cooling techniques that serve to significantly increase the duration of atomic coherence Fig. 1 (click here to see the figure)
In the past five years, the Quantum-Atom Optics (QAO) lab (in affiliation with the Thailand Center of Excellence in Physics or ThEP Center) has implemented several novel schemes anticipated to help sustaining basic research activity in Thailand, e.g. making money work more than its value, entering the topmost research rings on a budget, collaborating through student internship and shaping up atomic physics entrepreneurship. Finally yet importantly, we have spent most of the time on developing own technologies for experimental atomic physics as well as designing and building research equipment most necessary for running an atomic lab. Engineering skills gained not only reduce the cost for laboratory installation by at least 40% but also does make the QAO lab globally unique. At the moment, there are 14 devices we reckon as “good enough,” two of which have gone through packaging design and will be soon ready for production line.
On the 21st of December 2015, the QAO lab has demonstrated the capability to control all home-built devices to work in concert pertaining to atomic time scales. The first full characterization of our cold atomic ensemble has verified the sub-Doppler cooling (the Doppler limit in D2-line of rubidium-85 atom is ~150 µK) along which the FIRST MILESTONE, the recoil-limit temperature of 9 µK, has been finally reached and confirmed. Beyond this temperature, light plays no role in cooling no more and atoms colliding in the dark are termed "Ultra-cold." The ability to quantitatively extract physical entities from basic quantum bodies has paved the way for progressing toward the SECOND and THIRD MILESTONES, i.e. the SiAM trap and the single atom trap, respectively, expected by the first half of 2016.
We truly hope that all endeavors and devotions consistently exerted over years would help strengthening the AMO research collaboration and pushing forward Thai research community to the establishment of the national center for quantum technologies in no time. The communication report of the QAO timeline below Fig. 2 (click here to see the figure) is meant to be nothing more than a research legacy we attempt to preserve.
Some fact: Exciting a rubidium-85 atom with atomic mass 1.41 X 10-25 kg in D2-line F=3 -> F’=4 would require a photon at wavelength 780.241384 nm (8MHz red-detuned from the resonance peak as used in the MOT). This photon produces a momentum kick of 8.5 x 10-28 kg.m/s that changes the atomic velocity by 6.03 X 10-3 m/s. The atom would later spontaneously emit a photon at small difference in energy due to the Doppler shift in an average time of 2.6 X 10-8 s before the next absorption may occur 5.2 X 10-8 s later. The average deceleration per circle is 7.7 X 104 m/s2 which are about 7.8 x 103 times of the Earth’s gravitational pull. In an analogy, a human mass of 70 kg would weigh equivalent to an Airbus A380 when taking off! Cooling a rubidium-85 atom from room temperature (20oC) down to close to stop only takes 4.43 X 10-3 s. In the QAO lab, gaseous rubidium with mean free path of 2.82 x 105 m can be easily produced by decreasing the atomic density to 3.55 x 106 atoms/cm3. The pressure of 10-10 torr would be like sitting on the Moon without an astronaut suit. When atomic collisions are rare and the temperature is ultra-cold, it is possible to compress 1010 rubidium-85 atoms and confine them in a volume of 10-2 cm3. This number is about one order lower than the number of all observable stars in the Milky Way. Picking out an atom out of 10 trillion and taking a picture are ambitious. However what makes this endeavor worthwhile is the control over the trapped single atoms.
Reported by :
Dr. Waranont Anukool
Quantum-Atom Optics Lab, Department of Physics and Materials Science,
Faculty of Science, Chiang Mai University, Chiang Mai-50200, Thailand