Atoms with quantum memory

Feb 28, 2013
The Atom chip (above) - in the background the measured distributions are shown, whicht characterize the quantum physical state of the condensate.

Order tends towards disorder. This is also true for quantum states. Measurements at the Vienna University of Technology show that in quantum mechanics this transition can be quite different from what we experience in our daily lives.

Ice cubes in a cocktail glass melt until an equilibrium state is reached in which the ice cubes are gone. After that, the of the ice cubes is completely lost. The liquid does not contain any memory of their shape, the ordered ice crystal has turned into disordered . Ultra cold Bose-Einstein condensates behave differently; these highly ordered clouds of ultra cold particles also approach a disordered equilibrium state, but they retain some "memory" about their initial state for a remarkably long time. This phenomenon does not depend on the temperature, it seems to be a stable, fundamental property of .

Stopover on the way to chaos

In 2012, the research group around Professor Jörg Schmiedmayer at the Vienna Center for and Technology (VCQ), Vienna University of Technology, were able to show that they have found an intermediate state between order and disorder; the atoms of an ultra cold tend towards an equilibrium state, in which their quantum physical properties are not visible any more.

Melting ice cubes: all the information about the geometry is lost when the ice melts.

This, however, does not happen continuously like the transition from an ice cube to . Instead, there is an intermediate step called "prethermalized state", in which the atoms remain for a surprisingly long time without forgetting about their quantum mechanical origin. "If we split the atom cloud into two parts and recombine them after some time, a wave pattern forms", Jörg Schmiedmayer explains. "That is proof that the atom clouds still contain information about having emerged from a highly ordered quantum physical state."

Intermediate state independent of temperature

Now the scientists have managed to take a closer look at this transition – and it turns out to be remarkably stable with respect to external conditions. From experience, we are used to the opposite case: "Imagine a room full of air, and a vacuum in the room next to it", says Max Kuhnert (Vienna University of Technology). "When we open a door between those rooms, the system approaches an equilibrium, until the molecules are evenly distributed in the two rooms. This transition, however, strongly depends on external parameters such as pressure and temperature." The higher the pressure and the temperature, the faster information about the initial state is lost – be it information about the initial distribution of air molecules or about the geometry of melting ice cubes.

Wave pattern, created by the interference of atom clouds.

"The prethermalized state of our atom clouds is reached quite independently from pressure and temperature", says Max Kuhnert. The experiments, which have now been published in Physical Review Letters, show that this state is characterized by a new length scale. This so-called correlation length is a direct measure of the quantum memory of the ordered initial state. It is the length scale on which the quantum physical properties of the atom clouds can still be perceived.

Vacuum chamber, containing the atom chip.

"This emergent correlation length is defined by the density of the initial quantum gas, but it only becomes visible in the dynamics of the transition from an ordered state into the prethermalized state" says Jörg Schmiedmayer. "The fact that this correlation length does not depend on the initial temperature at all strongly indicates that the prethermalized state is a of quantum physics and has major significance", Max Kuhnert believes.

A deeper understanding of this is expected not only to explain ultra cold Bose-Einstein condensates, it may also shed some light on the processes in the early universe, or it could help to understand phenomena in the quark-gluon-plasma created in high energy particle accelerators.

Explore further: Interview with Gerhard Rempe about the fascination of and prospects for quantum information technology

More information: arxiv.org/abs/1211.5323

Related Stories

Ultracold atoms reveal surprising new quantum effects

Sep 06, 2012

Vienna University of Technology physicists have studied the transition of quantum systems towards thermal equilibrium. They detected an astonishingly stable intermediate state between order and disorder. ...

Vienna physicists create quantum twin atoms

May 02, 2011

At the Vienna University of Technology, sophisticated atomchips have been used to create pairs of quantum mechanically connected atom-twins. Until now, similar experiments were only possible using photons.

The diamond’s quantum memory

Aug 10, 2011

For years, quantum computers have been the holy grail of quantum technology. When a normal computer has to solve a number of problems, it can only execute them one after the other. In contrast, a quantum computer ...

Recommended for you

Could 'Jedi Putter' be the force golfers need?

10 hours ago

Putting is arguably the most important skill in golf; in fact, it's been described as a game within a game. Now a team of Rice engineering students has devised a training putter that offers golfers audio, ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

vacuum-mechanics
1.5 / 5 (8) Feb 28, 2013
…. Instead, there is an intermediate step called "prethermalized state", in which the atoms remain for a surprisingly long time without forgetting about their quantum mechanical origin. "If we split the atom cloud into two parts and recombine them after some time, a wave pattern forms….
…."The fact that this correlation length does not depend on the initial temperature at all strongly indicates that the prethermalized state is a fundamental property of quantum physics and has major significance", Max Kuhnert believes….

Maybe understanding the mechanism which explains how the quantum waves of atom was created (as below) could help to settle the matter.
http://www.vacuum...19〈=en
Antoweif
2.7 / 5 (7) Feb 28, 2013
...but it didn't. Stop advertising your useless site.
Tektrix
2 / 5 (1) Feb 28, 2013
Sadly, the autologous ego-stroking of alternative-physics evangelists has become a hallmark of PhysOrg.
Tausch
1 / 5 (1) Feb 28, 2013
Correlation length. Check.
The fundamentals underlying Quantum Reality - QR - begins.
Trekkies eat your hearts out. You were either dead or alive, not both.
Probability space. The last frontier.
Substituting suspense with superposition without loss of excitement.

Oh, almost forgot. That interference you see...well there's dual nature to that - the amount of scatter rate is fundamental as well - at ANY temperature.

"no matter what the temperature or the particle, the rate at which they bounce off each other – 'scatter'– changes by the same amount as the temperature is changed."

Read more at: http://phys.org/n...html#jCp
Tausch
1 / 5 (2) Feb 28, 2013
The consequences of QR are beyond imagination.
Remember thermodynamics? The 'laws' that can not be derived? Because there was no theory for the 'laws' to be derived from?
The 'laws' that never have, never do, and never will contradict all observations?

Now there is a reality from which those 'laws' can be derive.
Yes. We live in exciting times.

More news stories

Could 'Jedi Putter' be the force golfers need?

Putting is arguably the most important skill in golf; in fact, it's been described as a game within a game. Now a team of Rice engineering students has devised a training putter that offers golfers audio, ...

Treating depression in Parkinson's patients

A group of scientists from the University of Kentucky College of Medicine and the Sanders-Brown Center on Aging has found interesting new information in a study on depression and neuropsychological function in Parkinson's ...