Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Squeezed quantum cats

27.05.2015

Quantum physics is full of fascinating phenomena. Take, for instance, the cat from the famous thought experiment by the physicist Erwin Schrodinger. The cat can be dead and alive at once, since its life depends on the quantum mechanically determined state of a radioactively decaying atom which, in turn, releases toxic gas into the cat's cage. As long as one hasn't measured the state of the atom, one knows nothing about the poor cat's health either - atom and kitty are intimately "entangled" with each other.

Equally striking, if less well known, are the so-called squeezed quantum states: Normally, Heisenberg's uncertainty principle means that one cannot measure the values of certain pairs of physical quantities, such as the position and velocity of a quantum particle, with arbitrary precision. Nevertheless, nature allows a barter trade:


The scientists used this ion trap to create the new quantum states.

Credit: ETH Zurich

If the particle has been appropriately prepared, then one of the quantities can be measured a little more exactly if one is willing to accept a less precise knowledge of the other quantity. In this case the preparation of the particle is known as "squeezing" because the uncertainty in one variable is reduced (squeezed).

Schrödinger's cat and squeezed quantum states are both important physical phenomena that lie at the heart of promising technologies of the future. Researchers at the ETH were now able successfully to combine both in a single experiment.

Squeezing and shifting

In their laboratory, Jonathan Home, professor of experimental quantum optics and photonics, and his colleagues catch a single electrically charged calcium ion in a tiny cage made of electric fields. Using laser beams they cool the ion down until it hardly moves inside the cage. Now the researchers reach into their bag of tricks: they "squeeze" the state of motion of the ion by shining laser light on it and by skilfully using the spontaneous decay of its energy states.

Eventually the ion's wave function (which corresponds to the probability of finding it at a certain point in space) is literally squashed: now the physicists have a better idea of where the ion is located in space, but the uncertainty in its velocity has increased proportionately. "This state squeezing is an important tool for us", Jonathan Home explains. "Together with a second tool - the so-called state-dependent forces - we are now able to produce a "squeezed Schrödinger cat" ".

To that end the ion is once more exposed to laser beams that move it to the left or to the right. The direction of the forces induced by the laser depends on the internal energy state of the ion. This energy state can be represented by an arrow pointing up or down, also called a spin. If the ion is in an energy superposition state composed of "spin up" and "spin down", the force acts both to the left and to the right. In this way, a peculiar situation is created that is similar to Schrödinger's cat: the ion now finds itself in a hybrid state of being on the right (cat is alive) and on the left (cat is dead) at the same time. Only when one measures the spin does the ion decide whether to be on the right or on the left.

Stable cats for quantum computers

The Schrödinger cat prepared by professor Home and his collaborators is special in that the initial squeezing makes the ion states "left" and "right" particularly easy to distinguish. At the same time, it is also pretty large as the two ion states are far apart. "Even without the squeezing our "cat" is the largest one produced to date", Home points out.

"With the squeezing, the states "left" and "right" are even more distinguishable - they are as much as sixty times narrower than the separation between them". All this isn't just about scientific records, however, but also about practical applications. Squeezed Schrödinger cats are particularly stable against certain types of disturbances that would normally cause the cats to lose their quantum properties and become ordinary felines. That stability could, for instance, be exploited in order to realize quantum computers, which use quantum superposition states to do their calculations. Furthermore, ultra-precise measurements could be made less sensitive to unwanted external influences.

###

Literature reference

Lo HY, Kienzler D, de Clercq L, Marinelli M, Negnevitsky V, Keitch, BC, Home JP: Spin-motion entanglement and state diagnosis with squeezed oscillator wavepackets. Nature, 21 May 2015, doi: 10.1038/nature14458 [http://dx.doi.org/10.1038/nature14458]

Media Contact

Dr. Jonathan Home
jhome@phys.ethz.ch
41-446-333-166

 @ETH_en

http://www.ethz.ch/index_EN

Dr. Jonathan Home | EurekAlert!

More articles from Physics and Astronomy:

nachricht From rocks in Colorado, evidence of a 'chaotic solar system'
23.02.2017 | University of Wisconsin-Madison

nachricht Prediction: More gas-giants will be found orbiting Sun-like stars
22.02.2017 | Carnegie Institution for Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>