Vienna physicists create quantum twin atoms

May 2, 2011, Vienna University of Technology
An ultra cold Bose-Einstein condensate emits pairs of atoms in an atom-chip.

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.

Objects that are well separated in space but still cannot be understood separately belong to the profoundest mysteries of . Pairs of are prominent examples of such systems. They allow the of quantum states or tap-proof data transfer using . In future, such experiments will not be restricted simply to photons: at the Vienna University of Technology (TU Vienna), a method has been developed to create correlated pairs of using ultracold Bose-Einstein condensates. The results of the experiments have now been published in the journal .

Even Einstein did not like the idea of well-separated particles still being quantum mechanically connected. He called this phenomenon “spooky action at a distance”. However, since then, the startling predictions of quantum theory have been verified in countless experiments. Quantum particles can – even if they are far apart – still belong together and “share” certain physical properties. “This does not mean that by manipulating one particle we can at the same time change the other, as if they were connected by an invisible thread”, Professor Jörg Schmiedmayer (TU Vienna) says, “but still, we have to treat both particles as one single quantum system – and that opens the door to fascinating new experiments.” Jörg Schmiedmayer’s team at the Institute for Atomic and Subatomic Physics, TU Vienna carried out the experiments, while theoretical calculations were done by Ulrich Hohensteiner (Karl Franzens University, Graz, Austria).

In order to produce the quantum-correlated atoms, the scientists first create a . This exotic state of matter occurs at extremely low temperatures, at less than a millionth of a degree above absolute zero. In a Bose-Einstein condensate, the atoms are in the lowest possible energy state. “The key to success are our atomchips”, Thorsten Schumm (TU Vienna) explains. With perfectly tailored chip structures, atoms can be manipulated with incredible precision. It is possible to deliver single quanta of vibrational energy to the atoms of the ultracold Bose-Einstein condensate. When the atoms return to the lowest energy state, the condensate has to get rid of the surplus energy. “Because of the sophisticated design of our atomchips, the Bose-Einstein condensate is left with only one single way to dispose of its energy: emitting pairs of atoms. All other possibilities are forbidden by quantum mechanics”, Robert Bücker (TU Vienna) explains. According to the law of momentum conservation, the two atoms move in exactly opposite directions. This process is closely related to effects in special optical crystals, in which pairs of photons can be created (so-called “optical parametric oscillators”), but now massive particles can be used instead of light.

The emitted twin atoms cannot be understood in the same way as classical , such as debris scattered into all directions in an explosion. They are quantum mechanical copies of each other and only differ by their direction of motion. They form one common quantum object. One atom cannot be mathematically described without also describing the other. “We are going to use these atoms for exciting new experiments”, Schmiedmayer enthuses. “A fascinating new field of research is opening up which new insights and possible applications will evolve from. This cannot yet be foreseen. It is conceivable that these correlated atom beams will lead to new quantum measurement methods, with a precision far beyond the scope of classical physics.”

Explore further: Atom and its quantum mirror image

More information: R. Bücker et al., Twin-atom beams, Nature Physics, Advance Online Publication 01 May 2011. doi:10.1038/nphys1992

Abstract
In recent years, substantial progress has been made in exploringand exploiting the analogy between classical light and matter waves for fundamental investigations and applications1. Extending this analogy to quantum matter-wave optics is promoted by the nonlinearities intrinsic to interacting particles and is a stepping stone towards non-classical states2, 3. In light optics, twin-photon beams4 are a key element for generating the non-local correlations and entanglement required for applications such as precision metrology and quantum communication5. Similar sources for massive particles have so far been limited by the multi-mode character of the processes involved or a predominant background signal6, 7, 8, 9, 10, 11, 12, 13. Here we present highly efficient emission of twin-atom beams into a single transversal mode of a waveguide potential. The source is a one-dimensional degenerate Bose gas14 in the first radially excited state. We directly measure a suppression of fluctuations in the atom number difference between the beams to 0.37(3) with respect to the classical expectation, equivalent to 0.11(2) after correcting for detection noise. Our results underline the potential of ultracold atomic gases as sources for quantum matter-wave optics and should enable the implementation of schemes previously unattainable with massive particles.

Related Stories

Scientists make quantum breakthrough

April 20, 2011

(PhysOrg.com) -- Scientists have demonstrated for the first time that atoms can be guided in a laser beam and possess the same properties as light guided in an optical communications fiber.

Discovery could pave the way for quantum computing

March 18, 2010

(PhysOrg.com) -- Two experimental systems at the forefront of modern physics research -- a single trapped ion and a quantum atomic gas -- have been combined for the first time by researchers at Cambridge.

Recommended for you

Scientists produce 3-D chemical maps of single bacteria

November 16, 2018

Scientists at the National Synchrotron Light Source II (NSLS-II)—a U.S. Department of Energy (DOE) Office of Science User Facility at DOE's Brookhaven National Laboratory—have used ultrabright x-rays to image single bacteria ...

Quantum science turns social

November 15, 2018

Researchers in a lab at Aarhus University have developed a versatile remote gaming interface that allowed external experts as well as hundreds of citizen scientists all over the world to optimize a quantum gas experiment ...

Bursting bubbles launch bacteria from water to air

November 15, 2018

Wherever there's water, there's bound to be bubbles floating at the surface. From standing puddles, lakes, and streams, to swimming pools, hot tubs, public fountains, and toilets, bubbles are ubiquitous, indoors and out.

Terahertz laser pulses amplify optical phonons in solids

November 15, 2018

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg/Germany presents evidence of the amplification of optical phonons ...

0 comments

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.