This week 100TB brings you the highlights from the world of quantum physics: scientists create a new form of light in two dimensions and an AI performs a flawless Bose Einstein condensate Nobel Prize recreation.
A New Spin on Light
In physics we deal with certain quantities found in nature which are preserved, meaning they cannot be created or destroyed, but transferred. One of these quantities is the linear momentum of an object, which is the product of mass times its velocity. It is, in essence, a measure of the force it would require to bring a moving object to slow down – the bigger the object, the larger its momentum is, and the greater the force needed to bring it to a standstill.
Angular momentum is the “rotational analog” of linear momentum. Basically it is a measure of rotation. It is also a conserved quantity making it an important quantity in physics. The angular momentum is defined by the point of origin from where the particle distance is measured and the speed of rotation of a particle around a defined axis in relation to the moment of inertia, or “ a quantity dependent on the distribution of mass about the axis of rotation”.
In quantum mechanics, the angular momentum of a particle of light, or a photon, has always been an integer multiple of Planck’s constant, until now. Physicists at Trinity College Dublin’s School of Physics and the CRANN Institute, Trinity College, Professor Paul Eastham and his graduate Kyle Ballantine, have shown that light can exist in a new form where the angular momentum of a photon is one half of the value.
Prof Eastham commented: “We’re interested in finding out how we can change the way light behaves, and how that could be useful. What I think is so exciting about this result is that even this fundamental property of light, that physicists have always thought was fixed, can be changed.”
As light moves in a straight line, it simultaneously “twists” or rotates around its own axis. Being able to change the nature of angular momentum, hence creating a new form of light, will be highly relevant to the study of secure optical communications. The experiment was conducted in two dimensions rather than three, so the reduction in angular momentum is only possible in lower dimensions for now.
AI Robot Brings Atoms to a Stand Still
A team of physicists at the Australian National University have taught an AI how to reconstruct and improve the intricate process of creating a Bose-Einstein Condensate. The condensate is a super cold gas in which the atoms are brought almost to a standstill, creating varying interesting effects.
The physicists started the experiment by cooling the atoms, and then letting the AI proceed: “It then had to figure out how to apply its lasers and control other parameters to best cool the atoms down to a few hundred nanokelvin (i.e. a billionth of a second), and over dozens of repetitions, it found more and more efficient ways to do so.” The highly sensitive process was monitored by the AI and it managed to adjust multiple factors at once. This enables a new, fast and precise way to create Bose Einstein condensates.
Wishing you a nanophotonic spinning weekend!