Researchers from the University of Bonn have just shown how a single
atom can be split into its two halves, pulled apart and put back
together again. While the word "atom" literally means "indivisible,"
the laws of quantum mechanics allow dividing atoms - similarly to light
rays - and reuniting them. The researchers want to build quantum
mechanics bridges by letting the atom touch adjacent atoms while it is
being pulled apart so that it works like a bridge span between two
pillars.
Dividing atoms? |
| The
Bonn scientists working with Prof. Dr. Dieter Meschede from the
Institute for Applied Physics of the University of Bonn succeeded in
keeping a single atom simultaneously in two places that were more than
ten micrometers, or one hundredth of a millimeter, apart. |
What sounds like nuclear fission and radioactivity is, however, a
precision process using quantum mechanics. The laws of quantum
mechanics allow objects to exist in several states simultaneously. This
is what the so-called double-slit experiment is based on, where a
particle can go through two slits at the same time. The Bonn scientists
working with Prof. Dr. Dieter Meschede from the Institute for Applied
Physics of the University of Bonn succeeded in keeping a single atom
simultaneously in two places that were more than ten micrometers, or
one hundredth of a millimeter, apart. This is an enormous distance for
an atom. Afterwards, the atom was put back together undamaged.
The atom has a split personalityThe fragile quantum effects can only occur at the lowest temperatures
and with careful handling. One method is cooling a cesium atom
enormously using lasers – to a temperature of a tenth of a
million above absolute zero – and then holding it with another
laser. This laser beam is key to splitting the atom. It works because
atoms have a spin that can go in two directions. Depending on the
direction, the atom can be moved to the right or the left by the laser
like on a conveyor. Key is that the atom's spin can be in both
directions simultaneously. So, if the atom is moved to the right and
left at the same time, it will split. "The atom has kind of a split
personality, half of it is to the right, and half to the left, and yet,
it is still whole," explained Andreas Steffen, the publication's lead
author.
The parts compare their "experiences"
But you cannot see the split directly; if you shine a light on the atom
to take a picture, the split will collapse immediately. The atom can
then be seen in several images; sometimes on the left, sometimes on the
right - but never in both places. And yet, the split can be proved
successfully by putting the atom back together. Thus an interferometer
can be built from individual atoms that can, e.g., be used to measure
external impacts precisely. Here, the atoms are split, moved apart and
joined again. What will become visible, e.g., are differences between
the magnetic fields of the two positions or accelerations since they
become imprinted in the quantum mechanical state of the atom. This
principle has already been used to very precisely survey forces such as
the earth's acceleration.
Quantum systems as tools?
The Bonn scientists, however, are looking for something else:
simulating complex quantum systems. Many physicists have been hoping
for a long time to be able to simulate so-called topological isolators
or plant photosynthesis – phenomena that are hard to capture with
modern super computers – using small quantum systems. The first
steps on the way to such simulators could consist of modeling the
movement of electrons in solid bodies, thus gaining insights for
innovative electronic devices. Examples for this are Dirac motion of
electrons in a single graph-layer or the emergence of artificial
molecules from interacting particles. But for this purpose, individual
atoms would not only have to be well controlled, but also linked
according to quantum mechanical laws since where the crux of the matter
lies is exactly in a structure made up from many quantum objects.
A cog in a gearbox"For us, an atom is a well-controlled and oiled cog," said Dr. Andrea
Alberti, the team lead for the Bonn experiment. "You can build a
calculator with remarkable performance using these cogs, but in order
for it to work, they have to engage." This is where the actual
significance of splitting atoms lies: Because the two halves are put
back together again, they can make contact with adjacent atoms to their
left and right and then share it. This allows a small network of atoms
to form that can be used – like in the memory of a computer
– to simulate and control real systems, which would make their
secrets more accessible. The scientists believe that the entire
potential of controlling individual atoms this precisely will become
apparent over time.
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