A recent paper in the Physical Review Letters journal proposes a model of a self-organised one-dimensional lattice which does not require lasers to hold the atoms in place, unlike the case of optical lattices. Researchers have had a keen interest in studying self-organised lattices for several reasons.

The method proposed by the authors is to allow atoms to spread between two thin nanoscale optical fibres. These fibres act as nanophotonic waveguides – that is, pipes through which the electromagnetic field is channelled. The electromagnetic field leaks slightly out of the fibres. The leaking field interacts with the atoms and trap them along its length spaced evenly. The researchers go further and study what happens when the atoms are excited by lasers. They propose exciting the atoms using pump lasers.

By tuning the laser, the atoms would absorb light quanta and go to an excited state and then subsequently drop back to the ground state by emitting light. These emitted light quanta are channelled by means of the optical fibres (waveguide) and eventually will be absorbed by another atom. Thus the atoms can interact with one another and exchange momentum.

The authors have calculated the expected behaviour on tuning the strength of the interaction between atoms. When the frequency of the laser is less than optimal, the atoms form an evenly spaced row. When the interaction strength is varied, depending on the frequency of the laser, the lattice in a self-organised manner may expand, contract or split into two equal halves.

This is exciting because no external agency is used to keep them pinned at regular distances; it is entirely a result of their interactions with the waveguide and with each other through photon exchange.

The theory presents an exciting interface between optics and condensed matter physics and may contribute to yet another field – quantum computation, by suggesting a model for qubits (quantum bits) in a quantum computer.

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