On your wavelength

Achieving a Bose–Einstein Condensate from my living room during lockdown

During the COVID-19 lockdown which led to the closure of many labs around the world, Dr. Amruta Gadge, a postdoctoral researcher in the Quantum Systems and Devices group at the University of Sussex*, made headlines for remotely setting up a Bose–Einstein condensate from her living room. Here, she tells us her story.

When the UK government announced the national lockdown on 23rd March due to the pandemic, my lab at the University of Sussex was forced to temporarily close its doors.  We of course had a strong inkling this was coming, and rushed to get ourselves in order before it happened. In my laboratory, we were determined to keep our experiments going as best we could although we had never run them remotely before. Without being able to set foot in the labs, bar a few essential maintenance visits, the only way to continue working on our experiments was to use dedicated remote control and monitoring technology.

Dr Amruta Gadge adjusting a laser pre lockdown

Rebecca Bond

Pre-lockdown, I was part of a team building an apparatus to produce Bose-Einstein condensates (BECs).  A BEC consists of a cloud of hundreds of thousands of rubidium atoms, which have been cooled down to nanokelvin temperatures using lasers and magnetic fields.  At such temperatures the cloud suddenly takes on different characteristics, with all atoms behaving together as a single quantum object. This object has such low energy that it can be used to sense very low magnetic fields, a property we are making use of to probe   novel materials such as silver nanowires , silicon nitride nano membranes or to probe ion channels in biological cells.

We had started assembling this system just a few months before, and were looking forward to reaching a big milestone in the lab – producing our first BEC.  Time was short!  To run such an experiment from home was no easy feat, with large and complex laser and optics set-ups in state-of-the-art labs – which couldn’t just be transported.  In the days leading up to lockdown, equipment, chairs, and computers were being ferried to various homes, deliveries of equipment were diverted and protocols for remote access and online control were put in place.

Ultra-cold atom experiments are very complex. Obtaining a BEC involves a large amount of debugging and optimising of the experimental sequence. When not in the lab, at times it felt almost impossible to debug. We set up software control for the equipment, such as oscilloscopes, vacuum pumps, and others. However, the tool that played the most important role was our environmental monitoring system. Trapped cold atoms are extremely sensitive to any variations in the environmental conditions. Changes in the ambient temperature of the lab, humidity, residual magnetic fields, vacuum pressure, and so on, result in laser instability, polarisation fluctuations or changes in the trapping fields. All of these effects lead to fluctuations of the number of trapped atoms, as well as their position and temperature.

Debugging the system is a long process, but this can be greatly helped by monitoring the environmental conditions at all times. This may sound elaborate, however with the rising popularity of time series databases and data visualisation software, it is possible to develop a convenient monitoring system. We made use of cheap and easily programmable microcontrollers for data collection, and two popular open source platforms, InfluxDB and Grafana, for storing and visualising the data, respectively. We set up a large network of sensors throughout the labs, aimed at monitoring all the parameters relevant to the operation of the experiments. If atom numbers fluctuated, or something wasn’t performing well, we could quickly narrow down the problem by looking at our Grafana dashboards. This meant that our experimental control sequence could be quickly tweaked from home for compensating the environmental fluctuations, and the monitoring system proved to be an extremely useful tool in achieving BECs remotely.

Dr Amruta Gadge working from home with an image of her BEC on screen

Amruta Gadge

We were installing a new 2D magneto-optical trap atom source in the lab, and managed to see a signal from it just the day before the lockdown. I remember clearly that I was very worried that lockdown was going to delay the progress of our experiment significantly.  .  However, thankfully we could keep operating remotely, and managed to achieve our long-awaited first BEC from my home.

I was very excited when I saw the image of our first BEC. I had spent the whole day optimising the evaporation cooling stage. It was past 10pm, and I was about to stop for the day and suddenly the numbers started looking promising. I continued tweaking the parameters and in just few attempts, I saw the bimodal distribution of the atoms — a signature of a BEC. It was strange to have no one there to celebrate with in person, but we instead got together to hold celebrations virtually — something we are all getting used to now. I was really hoping to get the first BEC of our experiment before moving to my next post-doc, and having it obtained remotely turned out to be even more gratifying.

 

*Dr. Amruta Gadge is now a post-doctoral researcher in the cold atoms and laser physics group at the Weizmann Institute of Science, Israel.

 

 

 

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