Quantum 'trampoline' to test gravity

[Savwafair2012 Profile]

IT'S the world's smallest trampoline. Bouncing atoms with lasers could make ultra-precise measurements of gravity.

To test theories such as general relativity, the strength of gravity is measured precisely using ensembles of supercold atoms falling in a vacuum chamber. These ensembles are called "Bose-Einstein condensates".

BECs act in a quantum-mechanical wave-like fashion and interfere with each other. The interference pattern depends on the paths the atoms take, so gravity's effect on how fast they fall can be calculated by analysing the pattern with an interferometer. The longer the fall, the more precise the measurement – but the harder it is to keep the ensemble intact.

"The longer your interferometer, the more precise is your measurement," says Thomas Bourdel of the Charles Fabry Institute of Optics in Palaiseau, France. "But you are limited by the size of your apparatus."

Quantum fall
Now Philippe Bouyer of the Institute of Optics in Palaiseau, France, along with Bourdel and colleagues have increased the fall time with a "quantum trampoline".

In a microscopic chamber, they fired a specially designed laser pulse at the falling BECs. The pulse affected the BECs in the same way that a crystal lattice can affect light: since the atoms exhibit wave-like behaviour, they can be diffracted in a similar way to light in a crystal.

By tuning the laser, the team were able to split up the wave, causing some of its components to bounce upwards. When the parts fell back down, the laser was pulsed so they split again, and so on. Eventually the parts recombined in an interference pattern.

The device is less precise than existing atom interferometers, but the team plan to improve precision markedly by, for instance, using lighter atoms. Lighter atoms like helium and lithium will levitate for longer after each bounce than heavier atoms. This has the same effect as creating a longer interferometer with heavier atoms.

Journal reference: arxiv.org/abs/0911.0203

[Cryptillian Profile]

IT'S the world's smallest trampoline. Bouncing atoms with lasers could make ultra-precise measurements of gravity.

To test theories such as general relativity, the strength of gravity is measured precisely using ensembles of supercold atoms falling in a vacuum chamber. These ensembles are called "Bose-Einstein condensates".

BECs act in a quantum-mechanical wave-like fashion and interfere with each other. The interference pattern depends on the paths the atoms take, so gravity's effect on how fast they fall can be calculated by analysing the pattern with an interferometer. The longer the fall, the more precise the measurement – but the harder it is to keep the ensemble intact.

"The longer your interferometer, the more precise is your measurement," says Thomas Bourdel of the Charles Fabry Institute of Optics in Palaiseau, France. "But you are limited by the size of your apparatus."

Quantum fall
Now Philippe Bouyer of the Institute of Optics in Palaiseau, France, along with Bourdel and colleagues have increased the fall time with a "quantum trampoline".

In a microscopic chamber, they fired a specially designed laser pulse at the falling BECs. The pulse affected the BECs in the same way that a crystal lattice can affect light: since the atoms exhibit wave-like behaviour, they can be diffracted in a similar way to light in a crystal.

By tuning the laser, the team were able to split up the wave, causing some of its components to bounce upwards. When the parts fell back down, the laser was pulsed so they split again, and so on. Eventually the parts recombined in an interference pattern.

The device is less precise than existing atom interferometers, but the team plan to improve precision markedly by, for instance, using lighter atoms. Lighter atoms like helium and lithium will levitate for longer after each bounce than heavier atoms. This has the same effect as creating a longer interferometer with heavier atoms.

Journal reference: arxiv.org/abs/0911.0203

as far as i know the bose/einstein condensate is the only known particle that is a particle and wave at the same time.......different from photons which can switch between the two.

200 years ago if you were to postulate that atoms could exist as particles and act like waves at the same time they would have cut your head off.

i saw a program on NOVA that was about the quest for 'absolute zero' and the struggle to capture liquefied hydrogen 100+ years ago and even until recently the bose/einstein condensate was theoretical.

now they are using the condensate to prove various aspects of physics.

what an awsome world we live in now.

science at the speed of light

[Lucidlemondrop Profile]

I must say I was so surprised and impressed when I found a conversation here and not a pic of sexy girls on a trampoline..............

Not that such doesn't have a time and place, but hey, maybe we are getting back on track a bit here................

A quantum trampoline to me would be one where I would bounce out as far as I could and get boomeranged back into my earlier place, with the added experience of my expansion!