Physicists successfully demonstrate controlled transport of stored light

The controlled manipulation and storage of quantum information just as the capacity to recover it are essential prerequisites for accomplishing propels in quantum communication and performing corresponding computer operations in the quantum world.

Optical quantum memories, which allow for the storage and on-demand retrieval of quantum information carried by light, are essential for scalable quantum communication networks. For instance, they can represent essential building blocks of quantum repeaters or tools in linear quantum computing.

Using a technique known as electromagnetically induced transparency (EIT), incident light pulses can be trapped and coherently mapped to create a collective excitation of the storage atoms. Since the process is largely reversible, the light can then be retrieved again with high efficiency.

In a new study, a team of physicists led by Professor Patrick Windpassinger at Johannes Gutenberg University Mainz (JGU) has achieved a milestone in quantum physics. Physicists have demonstrated how light stored in a cloud of ultra-cold atoms can be transported using an optical conveyor belt.

They transported light stored in a quantum memory over a distance of 1.2 millimeters. Using ultra-cold rubidium-87 atoms as a storage medium for the light, the team has achieved a high storage efficiency level.

Professor Patrick Windpassinger, explaining the complicated process, said, “We stored the light by putting it in a suitcase so to speak, only that in our case the suitcase was made of a cloud of cold atoms. We moved this suitcase over a short distance and then took the light out again. This is very interesting not only for physics in general but also for quantum communication because the light is not very easy to ‘capture.’ If you want to transport it elsewhere in a controlled manner, it usually ends up being lost.”

Some time ago, the team developed a technique to ensemble cold atoms to be transported on an ‘optical conveyor belt,’ produced by two laser beams. This method allows a relatively large number of atoms to be transported and positioned with a high degree of accuracy without significant loss of atoms and without the atoms being unintentionally heated.

The physicists have now succeeded in using this method to transport atomic clouds that faint memory. The stored information can then be retrieved elsewhere.

Journal Reference:
  1. W. Li, P. Islam, P. Windpassinger, Controlled transport of stored light, Physical Review Letters 125, 150501, 8 October 2020, DOI:10.1103/PhysRevLett.125.150501
  2. M. Langbecker, P. Windpassinger, Kalte Atome auf einem optischen Förderband, Physik in unserer Zeit 50:1, 2 January 2019, DOI:10.1002/piuz.201970106
  3. M. Langbecker et al., Highly controlled optical transport of cold atoms into a hollow-core fiber, New Journal of Physics 20, 083038, 28 August 2018, DOI: 10.1088/1367-2630/aad9bb

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