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Showing posts with label atomtronics. Show all posts
Showing posts with label atomtronics. Show all posts

February 20, 2014

Atomtronic Progress - Bose Einstein condensate can display memory

While pursuing the goal of turning a cloud of ultracold atoms into a completely new kind of circuit element, physicists at the National Institute of Standards and Technology (NIST) have demonstrated that such a cloud—known as a Bose-Einstein condensate (BEC)—can display a sort of "memory."

The findings, featured as the cover article of the Feb. 12, 2014, issue of Nature, pave the way for a host of novel devices based on "atomtronics," an emerging field that offers an alternative to conventional electronics.

Just as electronic devices manipulate the flow of electrons, atomtronic devices manipulate the flow of atoms. Since atoms have properties that are very different from electrons, atomtronic devices have the potential to go beyond the capabilities of electronics. The newfound effect of the BEC could be an important tool for constructing atomtronic devices similar to computer memory, according to the research team's leader, Gretchen Campbell.

The atomtronic circuit could be useful in applications such as rotation sensors, playing the part that gyroscopes have in spacecraft and aeroplane navigation. The devices could also some day perform rudimentary quantum computations.

And because superfluidity in atoms is analogous to the way electrons flow without resistance in a superconductor, studying the transitions in atomtronics could drive theoretical work in superconductivity, says Campbell. Still, she acknowledges that practical devices are far in the future. “We’re still in the infancy of learning how to control our systems and what we can do. But that is our hope,” she adds.

Nature - Atom circuits a step closer, Ring-shaped flow of ultracold atoms remembers how it has been stirred

January 11, 2013

Analog of Electric Capacitance for Stored Neutral Atoms

First came electronics, the processing of information in terms of the charge of electrons flowing through circuits. Later a new form of tronics, spintronics, was invented to exploit the magnetic properties of electrons. Over the past decade or so still another information modality, atomtronics, has been under development, one employing not electrons but neutral atoms as the vehicle for information. The latest chapter in this development is the demonstration of a rudimentary atomtronic analog of capacitance.

Journal Nature Scientific Reports - Analogs of Basic Electronic Circuit Elements in a Free-Space Atom Chip

For more than a century the movement of electrons in circuits has been described in terms of three handy parameters: resistance, the energy lost by electrons in wires by scattering and heating; capacitance, the storage of energy in the circuit in the form of an excess of electric charge; and inductance, the storage of energy in the form of magnetic fields.

Dumbbell-shaped optical enclosure for atoms. (Courtesy JQI)


First Controllable Atom SQUID

Researchers have created the first controllable atomic circuit that functions analogously to a superconducting quantum interference device (SQUID) and allows operators to select a particular quantum state of the system at will.

By manipulating atoms in a superfluid ring thinner than a human hair the investigators were able for the first time to measure rotation-induced discrete quantized changes in the atoms’ state, thereby providing a proof-of-principle design for an “atomtronic” inertial sensor.



Absorption time-of-flight images show quantized stages in the central vortex. Images (e) and (f) show off-center vortices forming in the condensate when rotation speed exceeds a transition point, just as a voltage appears in a traditional Josephson junction when current exceeds a critical value.
Image Courtesy of Authors


August 21, 2012

First Atomtronic Radio Broadcasts Matter Waves

Arxiv - A Matterwave Transistor Oscillator

A triple-well atomtronic transistor combined with forced RF evaporation is used to realize a driven matterwave oscillator circuit. The transistor is implemented using a metalized compound glass and silicon substrate. On-chip and external currents produce a cigar-shaped magnetic trap, which is divided into transistor source, gate, and drain regions by a pair of blue-detuned optical barriers projected onto the magnetic trap through a chip window. A resonant laser beam illuminating the drain portion of the atomtronic transistor couples atoms emitted by the gate to the vacuum. The circuit operates by loading the source with cold atoms and utilizing forced evaporation as a power supply that produces a positive chemical potential in the source, which subsequently drives oscillation.

Oscillating circuits are the workhorses of many electronic devices. In particular, oscillating electrons emit electromagnetic waves, a mechanism that has lead to one or two applications that readers may have come across.

Seth Caliga and teams at the University of Colorado and National Institute for Standards and Technology in Boulder have built a version of this kind of circuit that works with atoms rather than electrons.

February 11, 2011

First Atomtronic sensor from a bose-einstein condensate shaped as a doughnut

This doughnut of ultracold gas spins without friction, creating a current of atoms that could be used to develop the first “atomtronic” sensors.

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 this ultracold gas to flow as 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.

In an upcoming paper in Physical Review Letters, the team reports creating this gas by cooling sodium atoms suspended in magnetic fields. The 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 doughnut with a radius of about 20 micrometers.

This site has covered atomtronics before

May 20, 2010

Open quantum systems approach to atomtronics

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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

Their atom-optical analogy to electronic circuits begins with the definition of the `atomtronic battery', which is composed of two reservoirs of ultracold atoms having different chemical potentials (corresponding to different electric potentials at the terminals of a conventional battery). The `wires' and atomtronic components are composed of optical lattices, and current refers to the number of atoms that pass a specific point in a given amount of time. The atomtronic diode is a device that allows an atomic flux to flow across it in essentially only one direction. 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.


the Colorado atomtronic researchers have published an Open quantum systems approach to atomtronics in Arxiv

We derive a quantum master equation to treat quantum systems interacting with multiple reservoirs. The formalism is used to investigate atomic transport across a variety of lattice configurations. We demonstrate how the behavior of an electronic diode, a field-effect transistor, and a bipolar junction transistor can be realized with neutral, ultracold atoms trapped in optical lattices. An analysis of the current fluctuations is provided for the case of the atomtronic diode. Finally, we show that it is possible to demonstrate AND logic gate behavior in an optical lattice.


October 09, 2009

Atomtronic Circuits of Diodes and Transistors

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

Their atom-optical analogy to electronic circuits begins with the definition of the `atomtronic battery', which is composed of two reservoirs of ultracold atoms having different chemical potentials (corresponding to different electric potentials at the terminals of a conventional battery). The `wires' and atomtronic components are composed of optical lattices, 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.



The 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. 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.


Dynamics of the atomtronic transistor.(a) A cartoon of the atomtronic transistor as a three-well system, where each well is connected to its own independent reservoir. (b) An energy schematic of the relevant states of the system under the assumed resonance condition. In both illustrated cases, there is a fixed chemical potential difference across the system. In case 1, the middle chemical potential maintains an occupancy of zero particles on the middle site and most of the population remains on the left site. In case 2, the base potential is raised to put one particle on the middle site. This triggers two competing cycles that, given weak coupling of the middle reservoir, causes an avalanche of current to flow across the system. (c) An exact calculation of the current responses of the atomtronic transistor. The middle reservoir here has one-tenth the coupling strength of the left and right reservoirs. For a fixed chemical potential difference across the device, we vary the middle potential and record the response of currents leaving the system from both the right site (blue) as well as out of the middle site (red). The differential current gain for this specific system is both large and essentially linear
Atomtronic Circuits of Diodes and Transistors in Physic Review Letters

From Physorg: Atomtronics probably won’t replace electronics. “Atoms are sluggish compared to electrons, and that means that you probably won’t see atomtronics replace current electronic devices. What atomtronics might be useful for is the field of quantum information.”

The dynamics of our atomtronic devices would be coherent and potentially useful in quantum computing.” He also suggests that there is the possibility that atomtronics could be useful in obtaining sensitive measurements. At the very least, he concludes, “atomtronic systems provide a nice test of fundamental concepts in condensed matter physics.”

While these ideas have been modeled, they have yet to be built. Pepino says that an effort is under way to set up experiments that could provide a proof of principle for the work being done at JILA and the University of Colorado by experimantal collaborator and co-author Dana Anderson.


We illustrate that open quantum systems composed of neutral, ultracold atoms in one-dimensional optical lattices can exhibit behavior analogous to semiconductor electronic circuits. A correspondence is demonstrated for bosonic atoms, and the experimental requirements to realize these devices are established. The analysis follows from a derivation of a quantum master equation for this general class of open quantum systems.



Atomtronics: Ultracold-atom analogs of electronic devices (from 2007)

Atomtronics focuses on atom analogs of electronic materials, devices, and circuits. A strongly interacting ultracold Bose gas in a lattice potential is analogous to electrons in solid-state crystalline media. As a consequence of the gapped many-body energy spectrum, cold atoms in a lattice exhibit insulatorlike or conductorlike properties. P-type and N-type material analogs are created by introducing impurity sites into the lattice. Current through an atomtronic wire is generated by connecting the wire to an atomtronic battery which maintains the two contacts at different chemical potentials. The design of an atomtronic diode with a strongly asymmetric current-voltage curve exploits the existence of superfluid and insulating regimes in the phase diagram. The atom analog of a bipolar junction transistor exhibits large negative gain. Our results provide the building blocks for more advanced atomtronic devices and circuits such as amplifiers, oscillators, and fundamental logic gates.