Atomtronics

An Ultracold Analogue of
Semiconductor Devices and Circuits

Introduction and Theory
Atomtronics 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 of
electronic 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 Behind
Atomtronics
Physicists Satyendra Nath Bose
and Albert Einstein proposed in 1924
that large numbers of atoms could be
chilled to the point that they joined
together in a single quantum state,
bringing subatomic effects to a scale
accessible by laboratory experiments. The First Pure Bose-
But it wasn’t until 1995 that scientists Eintein condensate
made a Bose-Einstein condensate was created by
(ultra-cold gas) using lasers to carefully
cool rubidium-87 atoms down Eric Cornell and
to temperatures less than a millionth Carl Wieman
of a degree above absolute zero. The
2001 Nobel Prize in Physics celebrated
this accomplishment, which was also
achieved using sodium atoms.

What is the Bose – Einstein
Condensation
• 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 Einstein's 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-Einstein
Condensation finally Made ?
• It took 70 years to realize Einstein's 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 Evolve
into 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 electron's spin, as well as it's 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 Both
Electronics and Spintronics in the quantum
computing 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 ultracold 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 battery
A voltage is applied by connecting the system to two reservoirs,
one of higher (left) and another of
lower(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

Reference
 Electronics for you (September 2010 issue)
 http://jila.colorado.edu/content/quantum-dynamics-
condensates-atomtronic-systems-and-photon-fluids
 http://nextbigfuture.com/2009/10/atomtronic-circuits-
of-diodes-and.html
 http://www.geeky-gadgets.com/why-is-atomtronics-
important-13-02-2011/
 http://cdsweb.cern.ch/record/966590
 http://martyscoolstuff.blogspot.com/2011/02/why-is-
atomtronics-important.html
 http://www.opticsinfobase.org/abstract.cfm?uri=LS-
2006-LMG2
 http://www.physorg.com/news174303837.html

Atomtronics

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