Researchers change the color and shape of a single photon

October 6, 2011
The color and shape of single photons produced by a quantum dot single photon source (QD SPS) are changed by combining them with a strong, pulsed pump laser in a nonlinear crystal (PPLN WG).

( -- A team of researchers from the CNST and ITL has simultaneously changed the color and shape of a single photon, the smallest unit of light.

The work, reported in the August 19 issue of Physical Review Letters, represents an important step towards implementing communication over long distances with privacy secured by the laws of .

Using a specially designed optical fiber probe, a single photon at a telecommunications wavelength was extracted from a quantum dot, a semiconductor analog of an atom, that was engineered to emit photons one at a time.

Each photon was then combined with a much stronger pulsed laser beam inside a nonlinear optical crystal that enables the two to interact efficiently.

After exiting the crystal, the wavelength, or color, of the photon is shifted by almost 600 nm, an amount greater than the size of the entire visible spectrum.

Because the researchers use a pulsed laser, its temporal shape becomes imprinted on the single photon during the color-conversion process.

Researchers utilizing different , which often require single photons of a specific wavelength and shape, may be able to use this approach to link their previously incompatible systems together in a large-scale network for applications.

Explore further: This little light of mine: Changing the color of single photons emitted by quantum dots

More information: Simultaneous wavelength translation and amplitude modulation of single photons from a quantum dot, M. T. Rakher, L. Ma, M. Davanço, O. Slattery, X. Tang, and K. Srinivasan, Physical Review Letters 107, 083602 (2011).

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5 / 5 (1) Oct 06, 2011
In the "related stories" column the same authors, the same research and the same institute are reported.
not rated yet Oct 06, 2011
a single photon at a telecommunications wavelength was extracted from a quantum dot, a semiconductor analog of an atom, that was engineered to emit photons one at a time.

Quick question, do quantum dots actually emit single photons in a fully controllable way, or do they just emit single photons at a low enough frequency (time between emissions) to be distinguished by the electronics?
not rated yet Oct 06, 2011
lol Quick ans. Yes.
The slower ans. The latter.
1 / 5 (2) Oct 06, 2011
in a fully controllable way
"Fully controllable way" sounds suspiciously in a quantum world due the quantum uncertainty - or not?

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