The technique “squeezes” quantum dots – tiny semiconductor particles a few nanometers in size that exhibit both optical and electronic properties – to emit single photons with precisely the same color and with positions that can be less than a millionth of a meter apart.
“This breakthrough,” says Allan Bracker, a chemist at NRL and one of the researchers on the project, “could accelerate the development of quantum information technologies and brain-inspired computing.”
In order for quantum dots to “communicate” (interact), they have to emit light at the same wavelength – a characteristic determined by the size of a quantum dot. However, say the researchers, just as no two snowflakes are alike, no two quantum dots have exactly the same size and shape – at least when they’re initially created.
This natural variability makes it impossible for researchers to create quantum dots that emit light at precisely the same wavelength [color], says NRL physicist Joel Grim, the lead researcher on the project.
“Instead of making quantum dots perfectly identical to begin with, we change their wavelength afterwards by shrink-wrapping them with laser-crystallized hafnium oxide,” says Grim. “The shrink wrap squeezes the quantum dots, which shifts their wavelength in a very controllable way.”
While “tuning” of quantum dot wavelengths has been demonstrated in the past, say the researchers, this is the first time it has been achieved precisely in both wavelength and position.
“This means,” says Bracker, “that we can do it not just for two or three, but for many quantum dots in an integrated circuit, which could be used for optical, rather than electrical, computing.”
This milestone in the manipulation of quantum dots, say the researchers, could lay the groundwork for future strides in a number of areas.
“NRL’s new method for tuning the wavelength of quantum dots,” says Bracker, “could enable new technologies that use the strange properties of quantum physics for computing, communication, and sensing. It may also lead to ‘neuromorphic’ or brain-inspired computing based on a network of tiny lasers.”
In addition, say the researchers, applications in which space and power-efficiency are limiting factors may also benefit from this breakthrough approach.
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