Design Research Optics

Physicists take steps toward delivering quantum information to the home

A tree network is often used to distribute classical data to homes via fiber optics. Researchers are working on co-propagating quantum information with the classical data to improve security. Image copyright: Iris Choi, et al. ©2011 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft

(PhysOrg.com) -- Today, fiber optics technology transports information in the form of classical data to homes and businesses. But researchers are currently working on ways to combine quantum data with the classical data in fiber optics networks in order to increase security. In a new study, scientists have shown how quantum and classical data can be interlaced in a real-world fiber optics network, taking a step toward distributing quantum information to the home, and with it a quantum internet.

The physicists, Iris Choi, Robert J. Young, and Paul D. Townsend, from the Tyndall National Institute at the University College Cork in Cork, Ireland, have published their study on combining quantum and classical signals in a recent issue of the New Journal of Physics . While the feasibility of transferring qubits on modern fiber-to-the-home (FTTH) networks has previously been demonstrated, this is the first time that researchers have investigated how the operation would work in a real-world network.

“I believe that our work constitutes the first really hard-nosed, pragmatic attempt to address the question of whether quantum key distribution (QKD) can work on a real fiber-to-the-home (FTTH) network,” Townsend told PhysOrg.com . “The new scheme that we have developed and tested demonstrates that the answer is ‘yes it can.’ I say pragmatic and hard-nosed because we have taken a widely deployed classical FTTH system and have adapted QKD to interwork with it, leaving the design of the classical part of the system essentially unchanged. The alternative approach, sometimes taken in QKD research, is to leave out the classical system completely or to adapt it to work with the QKD. In our view this is not very practical for cost reasons.”

The biggest challenge in transferring qubits in real-world networks is overcoming the crosstalk between the classical and quantum channels. Crosstalk is induced by spontaneous Raman scattering of photons in the optical fiber. Since the classical channels involve strong laser pulses while the quantum information is carried by single photons, the crosstalk primarily affects the quantum channel, making the error rate so high that the quantum channel is unable to operate.

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No Maksutov-Cassegrain telescopes need collimation?

I'm getting ready to buy my first serious telescope and have been investigating possible to find something that best suits me. One of the telescopes I am considering is using a Maksutov-Cassegrain design, but I can not find any info on if required as Newtonian Reflector Collimation. If they do occasionally require optical alignment, which is more difficult than with a reflector? And How often are required? Any other maintenance that requires that others do not? One of the reasons I'm leaning towards the Mak-Cass is its portability, as the telescope is best to make the most use. Also, my telescope was once a model of refraction of age in an equatorial mount, so I'm anxious to do Indeed, some of sight in one area of quality.

Unlike Cassegrains Ritchey and Schmidt, Maksutov-Cassegrains never need to be collimated by the user, and the tubes are sealed, and therefore also no need to clean the mirrors every time year or so as Newtonian done. However, at some point would to remove the film that can accumulate in the lens correction in time. Try as you would a camera lens, and not put the cleaning solution directly about the spelling! If he goes inside, you have a disorder that requires the telescope to be disassembled and cleaned before reassembly and collimation, which has to be done by an expert. These telescopes have succeeded, when the image quality that rivals apochromatic refractors of the same aperture, at a fraction of the price. They have no aberration chromatic field curvature, coma, astigmatism and very high image contrast. They are great for the moon, planets and double stars, and show no diffraction peaks around stars in the classic way Cassegrains, Newtonian and Dobsonians do. In fact, they are easy to mount steadily as well and no doubt they are portable. However, they have drawbacks, namely the long focal ratio, a narrow field of vision. That's not a problem for most deep sky objects, but not be able to fit large clusters of stars or galaxies in the field of vision, even with low-power eyepiece. The sealed tube also means they take longer to cool the surrounding air temperature. Until that happens, you will not get strong views. While it takes into account the cameras, the long focal ratio means longer exposures and that would be a problem to try to photograph a galaxy. The 6-inch and smaller Maksutov-Cassegrains are highly portable and are very good price. I recently looked at M-13 through a 5 "Mak and found the view was as good as my 6-inch F / 8 Newton, which has excellent optics. The group was well resolved globular and surprisingly bright for a 5-inch Maksutov given the amount of light the sky was contaminated.

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