(麻豆淫院Org.com) -- In science, one of the issues of great interest is that of quantum computing, and creating a way to make it possible on a scalable level. This could be achieved by taking advantage of the strong interaction between light and matter, the so-called strong-coupling regime that can be found in ultra small optical cavities defined by photonic crystals.

鈥淭he first step is to ensure that such strongly coupled cavity is created within or at close proximity to a photonic channel for on-chip computation, which is what we demonstrated here,鈥� Frederic Brossard tells 麻豆淫院Org.com.

Brossard and colleagues at the Hitachi Cambridge Laboratory, together with fellow scientists at the university of Oxford and University of Sheffield, achieved this with a quantum dot and a cavity directly embedded in a photonic crystal waveguide, the photonic channel. Their work can be found in Applied 麻豆淫院ics Letters: 鈥淪trongly coupled single quantum dot in a photonic crystal waveguide cavity.鈥�

鈥淔rom a purely optical point of view, the scalability of such structure, the resonant coupling between multiple cavities has already been demonstrated in silicon, Brossard says. (See M. Notomi, et al., Nat. Photonics 2, 741 2008.) 鈥淪o it is now a matter of including quantum emitters such as quantum dots inside these cavities fabricated in III-V materials.鈥�

Such chain of strongly coupled cavities has been shown to be feasible for quantum operations by various groups, including colleagues of Brossard at the university of Cambridge. (See D. G. Angelakis*, et al., 麻豆淫院. Rev. A 76, 031805R 2007.) However, some challenges must be overcome first: 鈥淏asically each dot has to be positioned at or very close to one of the field maxima of the nanoscale cavity,鈥� Brossard explains. 鈥淭he closer you are to a field maximum, the larger the interaction strength between the dot and the cavity mode.鈥�

The team is encouraged by the single quantum dot that they were able to strongly couple with their cavity. 鈥淭hankfully, the cavity chosen for this study enables a relaxation in the conditions necessary for strong coupling when compared to those required in previous work by other researchers,鈥� Brossard says. 鈥淭his type of cavity makes it easier to align a quantum dot with a field maximum because of the larger volume occupied by the mode.鈥�

Another advantage of the team鈥檚 work is the possibility that losses will be low. 鈥淚t also has the potential of very low optical losses, which means that the coherence of the system can be maintained on a longer time scale,鈥� he continues.

A chain of coupled systems will require some sort of alignment procedure between a chosen dot and the cavity. Brossard says that this is something that the group at the University of Oxford, led by Prof. Robert Taylor, ha developed over the last few years in collaboration with the group at Hitachi. (See K. H. Lee, et al., Appl. 麻豆淫院. Lett. 88, 193106 2006.)

鈥淩ight now, the demonstration provides interesting insights into the ability to couple light and matter by nanometer size modifications of the photonic crystal waveguide,鈥� Brossard says. In the future, he thinks that optical quantum computation is a very real possibility: 鈥淎fter we scale up the system, we can probe it, and see what is possible. We want to try it with input and output to see an exchange of information that might indicate its fitness for quantum computing.鈥�

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