An Ultracold Analogue ofSemiconductor Devices and Circuits
Introduction and TheoryAtomtronics is a branch of Science , Engineering and Technology that deals with the creation of analogues of electronic circuits and devices by the use of Atoms . Atomtronics is an emerging technology that offers a wide range of applications. In Atomtronics , The current carriers in electronics is replaced with Ultracold atoms . The Ultracold atoms have interesting properties that conventional materials lack – Superfluidity , SuperConductivity and Coherence. Being Cold they are well behaved enough to be manipulated by Lasers. They can be used to measure time on unimaginably short time scales, can carry out simple calculations and belived to form the basis of future quantum computing
The Motivation to construct and study atomtronic analogues ofelectronic systems comes from several directions• The Experimental atomtronics • neutral atoms in optical lattices can realisations promise to be be well isolated from the extremely Clean. Imperfection such environment , reducing de- as lattice defects or photons can be coherence. These combine a completely eliminated. This allows powerful means of state readout one to study an idealised system. and preparation , with methods for entanging atoms. Such systems• Atomtronics System are richer than have alll the necessary ingredients their electronic counterparts to be the building blocks of because atoms possess more quantum signal processors. The internal degrees of freedom than close analogies with electronic electronics and the interaction devices can serve as a guide in the between these can be widely search for new quantum varied from strong to information architectures , weak.Thus, One can Study including types of quantum logic repulsive,attractive and non gates that are closely tied with the interacting atoms in same conventtional architectures in experimental setup. electronic computers.
The Science BehindAtomtronicsPhysicists Satyendra Nath Boseand Albert Einstein proposed in 1924that large numbers of atoms could bechilled to the point that they joinedtogether in a single quantum state,bringing subatomic effects to a scaleaccessible by laboratory experiments. The First Pure Bose-But it wasn’t until 1995 that scientists Eintein condensatemade a Bose-Einstein condensate was created by(ultra-cold gas) using lasers to carefullycool rubidium-87 atoms down Eric Cornell andto temperatures less than a millionth Carl Wiemanof a degree above absolute zero. The2001 Nobel Prize in Physics celebratedthis accomplishment, which was alsoachieved using sodium atoms.
What is the Bose – EinsteinCondensation• In the early 1920s Satyendra Nath Bose was studying the new idea (at that time) that the light came in little discrete packets (we now call these "quanta" or "photons"). Bose assumed certain rules for deciding when two photons should be counted up as either identical or different. We now call these rules "Bose statistics" (or sometimes "Bose-Einstein statistics").• Einstein guessed that these same rules might apply to atoms. He worked out the theory for how atoms would behave in a gas if these new rules applied.• What Einsteins equations predicted was that at normal temperatures the atoms would be in many different levels. However, at very low temperatures, a large fraction of the atoms would suddenly go crashing down into the very lowest energy level and most of the atoms will be in the same quantum level.
How was the Bose-EinsteinCondensation finally Made ?• It took 70 years to realize Einsteins concept of Bose-Einstein condensation in a gas. It was first accomplished by Eric Cornell and Carl Wieman in Boulder, Colorado in 1995. They did it by cooling atoms to a much lower temperature than had been previously achieved. Their technique used laser light to first cool and hold the atoms, and then these atoms were further cooled by something called evaporative cooling.• The success of the Bose-Einstein condensation experiment , Opened the gates to the possibility of the development of Atomtronics technology. The BEC Apparatus
The Need for Electronics to Evolveinto Atomtronics Electronics is a field of Electron movement in the circuits governed by the use of wires , Silicon and Electricity. Until recently, electronics had been based on a single property of electronics – Their charge. But now the physicists are exploiting another Property – Electron Spin.(Spintronics)• Spintronics , The branch of electronics employing the property of Electron spin promises to revolutise the world of electronics beacause The idea is to use the electrons spin, as well as its charge. Electrons can spin in two directions (Spin-Up, Spin-Down, which is actually clockwise and anti-clockwise), and the spin is detectable as weak magnetic energyThere are many usages of Spintronics like MRAM a memory system based on Spintronics, and it promises to be a fast, small and non-volatile memory electrons lose any possible initial quantum state as they bounce around through the energy-dissipatingsemiconductor or metallic systems, they are ill-equipped for quantum computing.
Atomtronics could be better than BothElectronics and Spintronics in the quantumcomputing era• Even though the field of Atomtronics is still a theoritical field , But scientist believes that atomtronics can bring revolutionary revolutionary changes in the field of Advanced computing , The properties of condensed atoms offer a wide range of possible applications. The use of ultra- cold atoms allows for the coherent 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, similarto superconducting electronic devices.• In a new research in this field, researchers from the Joint Quantum Institute in Maryland took sodium atoms, suspended them in a magnetic field, and then trapped them using laser beams. They cooled this down (to a few billionths of a degree above absolute zero) which gave them a Bose-Einstein condensate — the atoms began to act as one quantum particle. The atoms were them flattened to a donut-shaped ring with a radius of about 20 micrometers. Then, using another set of laser, they managed to get the ring to spin - which it does without friction - so it could theoretically spin forever (or 40 seconds in that case, which is the lifetime of the condensate). This method could be used to build a new type of rotation sensor.
Optical Lattice• An optical lattice is simply a set of standing wave lasers. The electric field of these lasers can interact with atoms - the atoms see a potential and therefore congregate in the potential minima. In the case of a typical one- dimensional setup, the wavelength of the opposing lasers is chosen so that the light shift is negative. This means that the potential minima occur at the intensity maxima of the standing wave. Furthermore, the natural beam width can constrain the system to being one-dimensional.• An optical lattice is formed by the interface of counter-propogation laser beams , creating a spatially periodic polarization pattern . The resulting periodic pattern may trap neutral atoms. Atoms are cooled and congregate in the locations of potential minima.• Atoms trapped in the optical lattice may move due to quantum tunneling even if the potential well depth of the lattice points, exceeds to the kinetic energy of the atoms , which is similar to the electrons in a conductor.• things that conducts are entire ultracold atoms in an optical lattice instead of electrons in a crystalline lattice
Latest Developments in the field of Atomtronics and suggested Practical applications• Atomtronics has the goal of developing a one-to-one analogy of electronic systems, components and devices with ultracold atoms trapped in optical lattices It is being researched at the University of Colorado. The Atomtronic Anderson Group of Optical Physics• Atomtronics uses atoms in strange quantum states to power devices or computer memory. Using atoms intead of electrons to process information could change the world of Computing
Atomtronics in Quantum Computer• A quantum computer is a device for computation that makes direct use of quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. Quantum computers are different from digital computers based on transistors. Whereas digital computers require data to be encoded into binary digits (bits) , But In quantum computing we store a quantum state on an object, perform operations on the object and then read out the final state.• Atoms trapped in optical lattices (in Atomtronics Devices ) have been considered extensively for specific quantum computing schemes due to their inherent energy conserving characteristics. Therefore the dynamics of atomtronic devices would be coherent and potentially useful in quantum computing.
Atomtronics Devices• It has been concluded that atomtronic systems provide a nice test of fundamental concepts in condensed matter physics. While these ideas have been modeled,they are yet to be built. They are :- Atomtronic Battery Atomtronic Conductor Atomtronic diode Atomtronic Transistor
Atomtronic Battery• Experimentally, a battery can be created by establishing two separate large systems which act as reservoirs, each with its own constant chemical potential. These mayalso be lattices or other experimentally plausible systems, such as large harmonic traps, containing a large number of atoms. Changing the frequency of the harmonic traps, or adjusting the lattice height, can be used to tune the chemical potentials of these reservoirs. Each of these reservoirs can be connected to one end of the atomtronic system and current is then possible from the higher chemical potential system to the lower one. As shown in fig below ;• Schematic of atoms in a lattice connected to an atomtronic batteryA voltage is applied by connecting the system to two reservoirs,one of higher (left) and another oflower(right) chemical potential , Giving Rise to a current from left to right .
Atomtronics Conductor• An attractive feature of atomtronic materials is that their conductivity properties can be easily modified. The primary conductor for an atomtronic system is an optical lattice with no other external potentials. This corresponds to a wire in an electronic system.• And current refers to the number of atoms that pass a specific point in a given amount of time.
Atomtronic Diode• The atomtronic diode is a device that allows an atomic flux to flow across it in essentially only one direction. It is made by adding a potential step, which emulates a semiconductor junction (the boundary between p-type and n-type solid-state materials), to an energetically-flat optical lattice.• Atomtronic analogy to a simple diode circuit. The atomtronic analogy of a diode formed from the joining of p-type and n-type semiconductor materials. Electrons are replaced by ultracold atoms, the battery is replaced by high and low chemical potential reservoirs, and the metallic crystal lattices (the microscopic medium that the electrons traverse) are replaced by an optical lattice. The atomtronic diode is achieved by energetically shifting one half of the optical lattice with respect to the other.
Atomtronic Transistor• The desired function of an atomtronic transistor is to enable a weak atomtronic current to be amplified or to switch,either on or off, a much larger one and acts as an amplifier. Transistor action requires at least three lattice sites connected to three independent reservoirs. The resonance condition for this device is found to be an extension of the diode case to account for the third well: the left external energy is shifted above the middle site by the on-site interaction energy and is of equal energy to that of the right site.• By configuring the optical lattice in a manner researchers show that it is possible to recover the characteristics of the conventional electronic transistor in the atomic world.
Limitations of Atomtronics• Atomtronics is still a theoretical subject , And needs lot of development and research to make it a reality.• It is pointed out, however, that atomtronics probably won’t able to entirely replace electronics as atoms are sluggish compared to electrons. This means it might be difficult to replace fast electronic devices with sluggish atomtronic devices
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