New twisted laser beam can sculpt ultra-cold atoms into unusual shapes: ScienceAlert

Getting atoms to do what they want isn’t easy — but it’s at the heart of much of the groundbreaking research in physics.

The creation and control of new forms of matter is of particular interest and an active area of ​​research.

Our new study, Posted in physical review messageshas unveiled an entirely new way to sculpt ultra-cold atoms into different shapes using laser light.

Extremely cold atoms, cooled to temperatures close to absolute zero (-273 degrees Celsius), are of great interest to researchers because they allow them to see and explore physical phenomena that would otherwise be impossible.

At these temperatures, which are colder than outer space, groups of atoms form new mass state of matter (not solid, liquid or gaseous) known as Bose-Einstein capacitors (BEC). In 2001, physicists were He won the Nobel Prize To generate such a capacitor.

The defining characteristic of BEC is that its atoms behave very differently from what we normally expect. Instead of acting as independent particles, they all have the same (very low) energy and are coordinated with each other.

This is similar to the difference between photons (particles of light) coming from the Sun, which may have different wavelengths (energies) and oscillate independently, and those in lasers, which have the same wavelength and oscillate together.

In this new state of matter, the atoms act more like a single wave-like structure than a collection of individual particles.

The researchers were able to display wave-like interference patterns between two different BECs and even produce moving “BEC droplets”. The latter can be considered as Atomic equivalent of a laser beam.

moving drops

In our recent study, conducted with our colleagues Gordon Rub And the Gian Luca Ubowe examined how specially designed lasers can be used to manipulate ultracold atoms in BEC.

The idea of ​​using light to move objects is not new: when light falls on an object, it can exert a (very small) force. This radiation pressure is the principle behind it The idea of ​​solar sailsThe force that sunlight exerts on large mirrors can be used to propel a spacecraft through space.

However, in this study, we used a specific type of light that can not only “push” atoms, but also rotate them around, like “optical screwdriver“.

These lasers look like bright rings (or cakes) rather than dots and have a twisted (helical) wave front, as shown in the image below.

Illustration of twisted purple light waves.
Light carrying orbital angular momentum (OAM, m) “spins” as it moves. (Grant Henderson and Alison Yao)

Under the right conditions, when such a twisted light is shone on a moving BEC, the atoms in it are first attracted towards the bright ring before orbiting around it.

As the atoms rotate, both the light and the atoms begin to form droplets that rotate around the original direction of the laser beam before being ejected outward, away from the ring.

The number of drops is twice the number of light turns. By changing the number or direction of twists in the initial laser beam, we have complete control over the number of droplets formed, and the speed and direction of their subsequent rotation (see image below).

Illustration showing the transmission of light to BEC.
The twisted light shines on a moving BEC, sculpting it into a ring before breaking it into a number of BEC droplets that orbit around the direction of the light before releasing and twisting away. (Grant Henderson and Alison Yao)

We can even prevent the atomic droplets from escaping the loop so that they continue to spin longer, producing a form of an extremely cold atomic current.

cold atomic currents

This approach of shining twisted light through ultra-cold atoms opens up a new and simple way to manipulate the material and sculpt it into other unconventional and complex shapes.

is a generation”electronic circuits‘, where matter waves from ultracold atoms are directed and manipulated by optical and/or magnetic fields to form advanced equivalents for electronic circuits and devices such as transistors and diodes.

The ability to reliably manipulate the shape of a BEC will eventually help in the creation of atomtronic circuits.

Our atoms are so cold, here they behave like “Atomic Superconducting Quantum InterferometerIt has the potential to provide much higher hardware than conventional electronic devices.

That’s because neutral atoms lose less information than the electrons that normally make up the current. We also have the ability to change device features more easily.

Even more exciting, however, is the fact that our method allows us to produce complex electronic circuits that would be impossible to design using ordinary materials.

This could help design highly controllable and easily reconfigurable quantum sensors capable of measuring small magnetic fields that would otherwise be unmeasurable.

These sensors It will be useful In fields ranging from basic physics research to the discovery of new materials or the measurement of signals from the brain.Conversation

Grant HendersonPhD candidate in physics, University of Strathclyde And the Alison Yao– Senior Lecturer in Physics, University of Strathclyde

This article has been republished from Conversation Under a Creative Commons License. Read the original article.

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