This “atom chip” was a central part of the experiment that produced the first Bose-Einstein condensate in Australia. The “chip” consists of a silver foil mirror, mounted on an alumina substrate. The mirror foil has grooves cut into its surface which form a network of conductors used to produce magnetic fields.
Bose-Einstein condensates are a special form of matter that form when a gas of bosons is cooled to a temperature near absolute zero (0 Kelvin, or -273.14 Celsius). To cool a gas of particles to such an incredibly cold temperature two processes are performed. First, the gas of particles - in the case of this device, a gas of rubidium atoms - is bathed in laser light. The combination of the laser light and magnetic fields generated by the “chip” traps a cloud of atoms. As photons carry momentum, an atom that absorbs a photon as it is moving towards the laser will be slowed. Slowing all the atoms reduces the gas cloud to a temperature around 1/10,000 of a degree above absolute zero.
Following this, the laser beams are switched off and the now-cooled atoms are left trapped in a magnetic field and allowed to evaporatively cool. The magnetic field can be thought of as a bowl shape from which the higher energy - and thus higher-temperature - atoms can spill out from. The sides of the magnetic trap are then lowered, allowing cooler and cooler atoms to escape. This leaves only the coldest particles which have a temperature of around 100 nanoKelvin. At this temperature, the individual atoms become indistinguishable and form a single quantum entity. This is the Bose-Einstein condensate.
This form of matter was first proposed theoretically as a culmination of work between Satyendra Nath Bose, an Indian Bengali physicist, and Albert Einstein. Bose sent Einstein his theoretical work on the quantum statistics of photons, which were then expanded upon by Einstein to the notion of other particles creating overlapping ground states. It is from both their names that we derive the name of the condensate.
This item is part of the UQ Physics Museum ‘2015, International Year of Light’ Tour
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This item is part of the UQ Physics Museum ‘100 Years if Physics at UQ’ Tour
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