A flexible
control system

Ottó Elíasson

Former PhD Student in Experimental Physics

To conduct experiments with cold atomic clouds one needs a lot of dedicated technology. To interact with the atoms we use laserlight and microwaves of a specific frequency (color) and intensity, as well as magnetic fields of a certain strength. During a single run of our experiment, we need to capture, cool, manipulate and perform measurements on the atomic cloud. In our system, each experimental cycle takes about 30 seconds.

A screenshot of Alice, the experimental control system under operation.

To manage all commands necessary for controlling the devices in the course of the sequence we use a home built experimental control environment developed in LabView. The fundamental entity in Alice is the wave, which is a single command to a single device. The power of the program lies in the fact that many waves can be grouped into high-level blocks of commands, with only a few relevant variables open to the user. Thereby we shift the focus from the often unnecessary technical control details to physically relevant variables.

As an example of a block of commands, let’s consider what it takes to acquire a shadow image of an atomic cloud (also called absorption images [1], p. 74). This is the most common way of imaging an atomic cloud, where one makes an absorb light, and look at the shadow forming on your image. Afterwards one can rebuild an image of the cloud by analysing how much light is missing. One sends a pulse of light onto the cloud and must capture that light on a camera. The light must have a very specific frequency (color), matching with an electronic transition of the atom. We control the presence of the light, with a device called a shutter; the frequency with an Acousto-optical modulator; and we must tell the camera to take a picture. To take a single picture, we first tune the light to the correct frequency and simultaneously open the shutter so the light passes through. A signal is then sent to the camera to take a picture. In order to reconstruct the atomic cloud, one actually needs to take three different images. One with both the imaging light and the atomic cloud present, one with only the imaging light and the last one with neither the imaging light or the atomic cloud present. This series of commands are then grouped as a block, which can be slid into the sequence and shifted around at wish.

To learn more about how Alice control system contributes to ScienceAtHome mission of building a quantum computer see this talk by Jacob Sherson and Aske Thorsen at the National Instruments Week 2016:


[1] W. Ketterle, D.S. Durfee and D.M. Stamper-Kurn (1999). Making, probing and understanding Bose-Einstein condensates. arXiv:cond-mat/9904034.

Next, read about
Alice: the remote lab

Alice: A flexible experimental control system