|
|
|
|
|
Twisted Photons May Improve Optical ImagingFiltering noise photons through light entanglement |
By Gabriel Gache, Science News Editor
25th of March 2008, 11:54 GMT
Adjust text size:  
|
| |
In an already random quantum world, parasite signals could spell disaster for quantum information systems. Take the example of the quantum computers. Even the slightest noise signal could bring it to a complete halt. However, parasite signals may not be as bad as previously thought, according to Seth Lloyd from the Massachusetts Institute of Technology. Lloyd claims to have found a way to exploit noise signal in order to create new quantum imaging systems.
Let's imagine an optical microscope. An image of a specific object is only obtained if it is shined with light. Light is reflected on the surface of the object so that it returns to the observer,
thus an image is obtained. However, the technique only works if the process isn't affected by noise determined by random photon source that interfere with the reflected light, because reflected photons and photons of noise cannot be distinguished by conventional detectors.
Lloyd believes that a filtering technique to eliminate the photons of noise could be implemented with the help of the principle of entanglement. Light entanglement allows photons to interact with each other in a more intimate way than classical physics would allow. For example, light entanglement may give the photon pair characteristics that clearly show that they have been created in an entangled state, some kind of a memory of their past, if I may.
The technique proposed by Lloyd involves the use of one of the entangled photons as signal, to shine the object that is studied while the other photon, called ancilla, is used as reference. Thus, as the signal photon is being reflected back at the observer, it can be compared with its entangled partner, the ancilla, to create a accurate image of the object. On the other hand, if the ancilla does not present evidence of a previous entangled state while being compared with the signal photon, it is rejected as noise.
Calculations reveal that, for the technique to work, it would require 2^e times the degree of entanglement of the photons than that generated through conventional systems existent today. The degree of entanglement describes the number of modes of the electromagnetic field entangled between the two photons.
The degree of entanglement is not the problem, but the comparison of the ancilla with the signal photon is. Theoretically this can be done by high energy photon recombination inside photonic crystals, which reverse of the process that takes place during entanglement. If Lloyd's calculations are correct, then the recombination process should be easier in the case of entangled photons which bear a memory of the entanglement.
The problem is, this would mean that the signal photon and the ancilla should be put in the same place at the same time, something which is extremely hard to do with the technology today, but not totally impossible. In comparison with other quantum-information processes, the recombination of two entangled photons should be relatively easy and could even be used in future systems to enhance the performance of optical communications.
|
|
| Rating: |
|
Poor (1.4/5) |
5 vote(s) so far |
|
|
|
|
User opinions: |
 No user comments yet.  Be the first to express your opinion using the form below! |
|
|
