To use this gate, Kumar needs photons that are identical in every way except polarization, or the orientation of their electromagnetic fields.These "identical" photons are sent through optical fiber to the gate itself, a small maze of devices that route photons in different directions depending on their polarization. Passing through the maze causes certain photon pairs to become entangled. But not all photons make it through the gate; only when photons reach detectors on the other end, and the researchers can measure whether or not they are entangled, do they know the gate succeeded. The only way to know whether or not the gate worked is to wait until a collection of photons has been fired at it, says Carl Williams, coordinator of the quantum information program at the National Institute of Standards and Technology. "Most of the time the gate fails," he says. "It's a probabilistic thing." But when the gate fails, the researchers simply disregard the unentangled photons. "The great thing about this work," says Williams, "is that it's in fiber. This is a big deal because it could lead to distributed networks. ... The obvious application is for long-distance quantum communication between two smaller quantum computers." One of the crucial elements in a conventional optical network is a device called a repeater, which amplifies signals that have degraded over distance. Williams says that a quantum logic gate, such as the one that Kumar built, could be used in a circuit that amplifies a signal without losing the entanglement of the photons. "This is an important step toward constructing a quantum Internet," says Seth Lloyd, a professor of mechanical engineering at MIT and a leading researcher in quantum computation. "Such a network would have powers that the ordinary Internet does not," he says. "In particular, communication over the quantum Internet would be automatically secure." Lloyd notes that Kumar's paper illustrates how a simple quantum logic operation can be performed using individual photons. "The current paper represents a significant advance in the technology of quantum computation and quantum networks," he says. |
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Quantum Leap
07/17/2008
Comments
Shiladie on 04/16/2008 at 9:57 AM
35
also, with the qubit, is it simply taking the X^2 of binary we know and love and making it X^3 by adding a 3rd option? or is there more that I'm not understanding?
brunascle on 04/16/2008 at 1:47 PM
Web Developer
70
not really. from what i understand, a qubit is kind of like a bunch of regular bits blurred together. each of those bits can only be a 1 or 0.
and a quantum computer is kind of like a bunch of classical (binary) computers blurred together, all running the same algorithm at the same time. each one comes up with a different answer, and if the algorithm is set up right, the one answer you're looking for will stand out above the rest.
Maverick Page on 04/16/2008 at 12:54 PM
1
bugme on 04/16/2008 at 1:20 PM
6
LarryH on 04/17/2008 at 11:50 AM
Senior Editor
7
warplayer on 04/16/2008 at 1:18 PM
2
This article really helped me wrap my head around the basics of quantum computers. And this article is just a bit more challenging but provides a great basis:
http://antoine.frostburg.edu/chem/senese/101/quantum/
Enjoy :)
warplayer on 04/16/2008 at 1:21 PM
2
jmaximus9 on 04/17/2008 at 1:13 AM
32
mergatroid on 04/18/2008 at 7:01 PM
12
When was the word quantum first uttered in relation to the atomic world? More than eighty years ago?
Geez, let's get going, fellas! God forbid some Bangladeshi, or heavens to Mergatroid, a North Korean brilliantly writes the paper of Papers ...! The humiliation we'll pass on to future generations, and it'll never lie down.
desolation0 on 04/19/2008 at 12:13 PM
13
Unfortunately, quantum computing is one of the areas I've started to allow other people to learn about instead of taking it on myself. I may be able to wrap my head around it all with enough effort but I'm beginning to realize how little impact I have on the subject compared with other areas. The amount of effort it takes to become an expert in this particular field is better left to someone more passionate about it than myself. It's basically become the next subject ignored in a line that started with Greek Tragedy.