Saturday, April 1, 2023

Atomtronics trying to replace Electronics

We all have heard of electronics, mechatronics and maybe even spintronics, but the latest buzzword doing the rounds of physics labs is atomtronics—the science of creating circuits, devices and materials using ultra-cold atoms instead of electrons -- Dr S.S. Verma

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A consequence of the near-ideal experimental conditions for optical lattice systems is that theoretical descriptions for atomtronic systems can be developed from firstprinciples. This allows theorists to develop detailed models that can reliably predict the properties of devices.

2. Atomtronic systems are richer than their electronic counterparts because atoms possess more internal degrees of freedom than electrons. Atoms can be either bosons or fermions, and the interactions between these can be widely varied from short to long range and from strong to weak. This can lead to behavior that is qualitatively different to that of electronics.

Consequently, one can study repulsive, attractive or even non-interacting atoms in the same experimental setup. Additionally, current experimental techniques allow the detection of atoms with fast, state-resolved and near-unit quantum efficiency. Thus it is possible in principle, to follow the dynamics of an atomtronic system in real time.

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3. Neutral atoms in optical lattices can be well isolated from the environment, reducing de-coherence. These combine a powerful means of state readout and preparation, with methods for entangling atoms. Such systems have all the necessary ingredients to be the building blocks of quantum signal processors. The close analogies with electronic devices can serve as a guide in the search for new quantum information architectures, including novel types of quantum logic gates that are closely tied with the conventional architecture in electronic computers.

4. Recent experiments studying transport properties of ultra-cold atoms in optical lattices can be discussed in the context of the atomtronics framework. In particular, one can model the short-time transport properties of an optical lattice with the open quantum system formalism discussed here.

Latest developments
The atoms placed in an optical lattice, when super-cooled to form Bose-Einstein condensates, may form states analogous to electrons in solid-state crystalline media such as semiconductors. Impurity doping allows the creation of n- and p-type semiconductor analogue states, and an atomtronic battery can be created by maintaining two contacts at different chemical potentials. Analogues to diodes and transistors have also been theoretically demonstrated.

Although atomtronic devices have yet to be realised experimentally, the properties of condensed atoms offer a wide range of possible applications. The use of ultra-cold atoms allows for circuit elements, which further allow for the coherent flow of information and may be useful in connecting classical electronic devices and quantum computers.

The use of atomtronics may allow for quantum computers that work on macroscopic scales and do not require the technological precision of laser-controlled few-ion computing methods. Since the atoms are Bose condensed, they have the property of superfluidity and, therefore, have resistance-less current in which no energy is lost or heat is dissipated, similar to superconducting electronic devices. The vast knowledge of electronics may be leveraged to easily adapt to ultra-cold atomic atomtronic circuits.

Physicists have developed a new type of circuit that is little more than a puff of gas dancing in laser beams. By choreographing the atoms of the ultra-cold gas to flowas a current that can be controlled and switched on and off, the scientists have taken a step toward building the world’s first‘atomtronic’ device.

The research team used Bose-Einstein condensate to make atomtronic sensors. The team reports creating this gas by cooling sodium atoms suspended in magnetic felds. Researchers then trapped the atoms in a pair of crossed laser beams and further chilled the atoms to less than 10-billionths of a degree above absolute zero. The two beams also shaped the condensate that formed at these low temperatures into a flattened dough-nut with a radius of about 20 micrometre.

A second pair of lasers transferred energy to the dough-nut to start its rotation. Because atoms in the condensate behave as a single, coherent quantum particle, such a ring of the substance does not speed up or slow down gradually. It jumps between different speeds, much like a blender would, if it could change settings instantaneously.

The scientists chose the lowest setting for their ring; about one revolution every second. Because the condensate also happens to be frictionless, this ring should, in theory, rotate forever. Limited by technical diffiulties, the research team kept it going for about 40 seconds—the lifetime of their condensate.

Scientists believed that Bose-Einstein condensate could provide an extremely sensitive rotation sensor. They added a ‘weak link’ to their condensate ring—a barrier created by a blue laser that could speed up or shut down the flow. Theoretically, if the condensate were kept still and the barrier was attached to a rotating sensor, the barrier would cause a sudden jump in current at certain rotation speeds.



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