Countable cold clouds of atoms

Put some cold atoms in a closed magnetic 'bucket' - count how many you have, throw away the excess - and do it again and again with the same number of atoms. At IFA Jan Arlt's research group has developed a new and promising technique to assure that a known number of atoms can be reproduced time after time i cold atomic clouds. The results have been published in Physical Review Letters 12 August 2016. The paper has received the special honour of being an Editors' Suggestion in PRL, plus a background article in Physical Review Focus.

[Translate to English:] Digram af forsøgsopstillingen — [Translate to English:] Den kolde gas er fanget i den aflange (blå) 'skål' til venstre ved hjælp af et magnetfeltudstyr, som ikke er vist på tegningen. Laserlys sendes igennem gassen, hvorved vekselvirkningen mellem lyset og atomerne roterer lysets polarisering. Det sendes videre igennem et optisk system, hvor kun det roterede lys slipper igennem til et CCD kamera, som hurtigt tager en række billeder af det polariseringsdrejede lys. Metoden kaldes Faraday imaging. Hvert billede analyseres efterhånden som de optages, af et integreret kredsløb, som kaldes en FPGA (Field-Programmable Gate Array), og herfra sendes besked til RF-enheden, som 'åbner' fælden for at lukke få atomer ud ad gangen, hvorpå en ny billedserie bekræfter udfaldet af stabiliseringsproceduren. Fotodioden PD er med til at sikre, at laserens lysstyrke er konstant, så variationer her ikke ødelægger præcisionen i atomantallet.

15 August 2016 by Ole J. Knudsen

Ultra cold gasses are quite suitable for many experiments. At very low temperatures - far below the temperatures even in Outer Space - the atoms of the gas will form a Bose-Einstein-condensate; a state of matter where the atoms will 'melt together' into one large 'super' atom. This can be interesting both in basic research in quantum mechanics and nuclear physics and for precise measurements a.o. of gravity.

In the paper, titeled "Preparation of ultracold atom clouds at the shot noise level" the Aarhus group describes the development of a process enabling the creation of ultracold clouds of Rubidium atoms, where the variation in the number of atoms from one experiment to the next is less than 0,1%. This gives far better initial conditions in a wealth of other experiments, and the method is both fast and precise.

The Physical Review Focus article is here