Rochester physicist's quantum-'uncollapse' hypothesis verified

August 6, 2008

In 2006, Andrew Jordan, professor of physics and astronomy at the University of Rochester, together with Alexander Korotkov at the University of California, Riverside, spelled out how to exploit a quantum quirk to accomplish a feat long thought impossible, and this week a research team at the University of California at Santa Barbara has tested the theory, proving it correct.

Quantum particles behave in ways that from our everyday experience seem utterly impossible. For instance, quantum particles have wave-like properties and can exist in many places at once. Why the objects we see around us every day—in what physicists call the "classical" world—don't behave this way despite being made of these very same strange quantum particles is a deep question in modern physics.

Most scientists have believed that the instant a quantum object was measured it would "collapse" from being in all the locations it could be, to just one location like a classical object. Jordan proposed that it would be possible to weakly measure the particle continuously, partially collapsing the quantum state, and then "unmeasure" it, causing the particle to revert back to its original quantum form, before it collapsed.

Jordan's hypothesis suggests that the line between the quantum and classical worlds is not as sharply defined as had been long thought, but that it is rather a gray area that takes time to cross.

In a recent issue of Nature News, Postdoctoral Fellow Nadav Katz explains how his team put the idea to the test and found that, indeed, he is able to take a "weak" measurement of a quantum particle, which triggered a partial collapse. Katz then "undid the damage we'd done," altering certain properties of the particle and performing the same weak measurement again. The particle was returned to its original quantum state just as if no measurement had ever been taken.

Because theorists had believed since 1926 that a measurement of a quantum particle inevitably forced a collapse, it was said that in a way, measurements created reality as we understand it. Katz, however, says being able to reverse the collapse "tells us that we really can't assume that measurements create reality because it is possible to erase the effects of a measurement and start again."

Source: University of Rochester

Explore further: Partnership at a distance: Deep-frozen helium molecules

Related Stories

Partnership at a distance: Deep-frozen helium molecules

December 7, 2016

Helium atoms are loners. Only if they are cooled down to an extremely low temperature do they form a very weakly bound molecule. In so doing, they can keep a tremendous distance from each other thanks to the quantum-mechanical ...

Taking statistics to the quantum domain

November 9, 2016

(Phys.org)—The change point problem is a concept in statistics that pops up in a wide variety of real-world situations, from stock markets to protein folding. The idea is to detect the exact point at which a sudden change ...

First signs of weird quantum property of empty space?

November 30, 2016

By studying the light emitted from an extraordinarily dense and strongly magnetized neutron star using ESO's Very Large Telescope, astronomers may have found the first observational indications of a strange quantum effect, ...

Recommended for you

Researchers improve qubit lifetime for quantum computers

December 8, 2016

An international team of scientists has succeeded in making further improvements to the lifetime of superconducting quantum circuits. An important prerequisite for the realization of high-performance quantum computers is ...

A nano-roundabout for light

December 8, 2016

Just like in normal road traffic, crossings are indispensable in optical signal processing. In order to avoid collisions, a clear traffic rule is required. A new method has now been developed at TU Wien to provide such a ...

Electron highway inside crystal

December 8, 2016

Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their ...

7 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

deatopmg
1 / 5 (1) Aug 06, 2008
Is this a clue how quantum objects may also exist in other dimensions, i.e. the other 6 in Dirac's equation, and how classical objects may be shifted into one or more of those dimensions?
komone
not rated yet Aug 06, 2008
Would this mean that quantum crytographic techniques are not actually 100% secure as has been thought? i.e. Message interceptions could be made undetectable.
Alexa
Aug 07, 2008
This comment has been removed by a moderator.
visual
not rated yet Aug 07, 2008
seeing that the "original state" is by definition not measured and so unknown, how can they know the particle actually reverted to the same state and not a different unknown one?
drel
4 / 5 (1) Aug 07, 2008
"...he is able to take a "weak" measurement of a quantum particle, which triggered a partial collapse..."

What measurement are they making (polarization, spin, momentum, position, etc) and what is meant by a "weak" measurement? I would like a bit more information please.

I'm not a physicist, but I did sleep in a hotel last night...
thales
3 / 5 (1) Aug 07, 2008
My first thought was that this is a blow to the Many Worlds Interpretation. In fact, according to http://www.hedweb...urement,
worlds only split off due to irreversible decoherence, which clearly is not happening here. I am very curious as to what multiple "weak" measurements of the same quantum particle would tell us. It seems to me that would give us insight to whether the MWI is correct (in which case each measurement yields different information) or incorrect (in which case each measurement yields the same info).
yp_me
not rated yet Aug 07, 2008
OK, here are my 2 dollars: I read Nature article and see possible problem: They check "un-collapse" by measuring energy distribution, but it is not full information about wave-function, there is also phase, which they most certainly destroyed by their "partial collapse" measurement. I bet standard interpretation will stand.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.