On-off atomic: Optical data transfer

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  • Published: Dec 15, 2015
  • Author: David Bradley
  • Channels: Atomic
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Experimental set-up  The rubidium atoms are trapped around the optical nanofibre and absorb light of wavelength 780 nm and 776 nm that has tunnelled out of the nanofibre. This effect can be used to create on/off switches. Credit: OIST Press Office

Researchers in Japan have developed an atomic on-off switch with ultrathin optical fibres, which could be used for data transfer in the future.

Binary underpins our digital world, its 1s and 0s are represented by ons and offs of billions of microscopic switches. Now, researchers in the Light-Matter Interactions Unit led by Síle Nic Chormaic of the Okinawa Institute of Science and Technology Graduate University (OIST) have developed an on-off switch using ultrathin optical fibres. Writing in the New Journal of Physics, they suggest that the approach could be critical to high-speed data transfer of the future that far outstrips the conventional fibre optic communications of today.

The OIST researchers have a far more efficient approach to those 1s and 0s that does not involve switching the light beam on and off rapidly, instead they have created an on-off switch based on the quantum characteristics of rubidium atoms in the presence of light of different wavelengths. Their proof-of-concept system could be used as a building block in a quantum network that might allow us to build a new class of data network.

OIST setup

The OIST team's setup consists of two lasers that produce light at different wavelengths, an optical nanofibre acts as a 350 nanometre thick waveguide with the rubidium atoms trapped around it. At this diameter the light is not entirely contained within the waveguide as it is of longer wavelength than the diameter of the fibre. As such, it can interact with the surrounding rubidium atoms and their properties can thus be modulated by the light and they can thus act as a quantum node, a redistribution point within a network.

The off switch condition is obtained when only the laser producing 780 nm is on. In this case, at the point where light spills beyond the boundaries of the optical nanofibre, the rubidium atoms absorb the maximum amount of light and almost no light can continue to pass along the fibre. Conversely, when it is operating with both 776 and 780 nm lights, most of the light is transmitted through the optical nanofibre and the rubidium atoms absorb only a minimal amount of light. Since the optical nanofibre is directly connected to a standard optical fibre, the light can, in principle, be transferred to another quantum system or node some distance away.

Optical nanofibres

"Using optical nanofibres would allow us to fully integrate our system with existing fibre-based communication networks. While the current work is far from being a practical solution to quantum information, it brings the notion of using atoms and light to develop real devices based on quantum mechanics ever closer to fulfilment," explains Nic Chormaic.

Of course, quantum computing is all about superposition of states, and while this current system generates 0s/off and 1s/on sequentially, further development might one day exploit the quantum behaviour of these or other clusters of atoms and their interaction with light so that dual states can be used simultaneously for greater data transmission speeds and for applications that scientists are yet to consider. In this way, in the future, quantum networks will be able to process more data simultaneously, increase efficiency of information transfer and also provide better cyber security.

"It has been very exciting to work with optical nanofibres which can guide light extremely efficiently even if their diameter is much smaller than the wavelength of light itself," explains team member Ravi Kumar of University College Cork, Ireland. "These systems are sure to give us significant progress in quantum networks in the years to come," he adds.

"The next step in the work is to use more complex optical mode profiles propagating through the optical fibre that carry a property known as "orbital angular momentum". These beams are termed "doughnut beams" when travelling through free-space. They would give us an additional degree of freedom for any information that may be transferred via the fibre to the atoms," Nic Chormaic told SpectroscopyNOW. "Ultimately, we'd like to achieve quantum state transfer from one ensemble of atoms to another ensemble of atoms mediated by the optical nanofibre. For this, we need to improve our control over the atomic states within the ensemble, and this is our short-term target."

Related Links

New J Phys 2015, 17, 123012: "Multi-level cascaded electromagnetically induced transparency in cold atoms using an optical nanofibre interface"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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