How To Encode 2.05 Bits Per Photon, By Using Twisted Light

Thorfinn.au writes Researchers at the University of Rochester and their collaborators have developed a way to transfer 2.05 bits per photon by using "twisted light." [Abstract here.]This remarkable achievement is possible because the researchers used the orbital angular momentum of the photons to encode information, rather than the more commonly used polarization of light. The new approach doubles the 1 bit per photon that is possible with current systems that rely on light polarization and could help increase the efficiency of quantum cryptography systems.

Comments

I can't be the only one wondering

[Anonymous Coward]

How do you have a fraction of a bit?

Re:I can't be the only one wondering

[Anonymous Coward]

205 bits per 100 photons.

Re:I can't be the only one wondering

[Anonymous Coward]

Come on, 41 per 20 is so much simpler.

Re:I can't be the only one wondering

[RightwingNutjob]

Oh come on. You could have said Shroedinger's child and gotten modded way funnier.

Re:I can't be the only one wondering

[ArcadeMan]

And 42 would be so much funnier.

Re:I can't be the only one wondering

[rossdee]

"How can you have 1.5 children per household?"

Shared custody, happens quite a bit these days.

Re:I can't be the only one wondering

[sribe]

I'm wondering how the conventional logic at either end of the process would manage to cope with three values. Can hardware be designed to work with more than on/off one/zero logic, i.e. perhaps one reaction for zero volts, another reaction for 2 volts, and a third reaction for 4 volts.

Dude, analog modems have been coding multiple bits per transition for DECADES, using both amplitude and phase to encode multiple values per transition. As do cable modems, DSL, and so on. Just about every transmission encoding method for the past 30 years...

In the example of 3 values, you get 0, 1 or 2. Then on the next transition, multiply by 3 and add 0, 1, or 2. And so on. That's simplified, because in fact there's typically more states than values, and mapping of states -> values involves techniques to mitigate the effects of interference.

Re:I can't be the only one wondering

[K. S. Kyosuke]

Inflation.

Re:Telecom use?

[Anonymous Coward]

Infinite-capacity wireless vortex beams carry 2.5 terabits per second

American and Israeli researchers have used twisted vortex beams to transmit data at 2.5 terabits per second. As far as we can discern, this is the fastest wireless network ever created — by some margin. This technique is likely to be used in the next few years to vastly increase the throughput of both wireless and fiber-optic networks.

These twisted signals use orbital angular momentum (OAM) to cram much more data into a single stream. In current state-of-the-art transmission protocols (WiFi, LTE, COFDM), we only modulate the spin angular momentum (SAM) of radio waves, not the OAM. If you picture the Earth, SAM is our planet spinning on its axis, while OAM is our movement around the Sun. Basically, the breakthrough here is that researchers have created a wireless network protocol that uses both OAM and SAM.

New Optical Fiber Puts a Twist on Data Transmission
“For several decades since optical fibers were deployed, the conventional assumption has been that OAM-carrying beams are inherently unstable in fibers,” said BU engineering professor Siddharth Ramachandran, who designed the new fiber. “Our discovery of design classes in which they are stable has profound implications for a variety of scientific and technological fields that have exploited the unique properties of OAM-carrying light, including the use of such beams for enhancing data capacity in fibers.”

The strategy by Ramachandran, Willner and colleagues, OAM mode-division multiplexing, combines both approaches. They packed several colors into each mode and used multiple modes. Unlike in conventional fibers, OAM modes in these specially designed fibers can carry data streams across an optical fiber while remaining separate at the receiving end.

Ramachandran’s OAM fiber had four modes (an optical fiber typically has two), and he and Willner showed that for each OAM mode, they could transmit 400 Gb/s in just a single wavelength of light — or 1.6 Tb/s across 10 wavelengths — over the course of 0.68 miles (1.1 km).

How To Encode 4 Bits Per Photon, By Using Colors

[Anonymous Coward]

An Anonymous Coward at Slashdot have developed a way of transfer 4 bits per photon by using "different colors". This remarkable achievement is possible because the anonymous coward used the wavelength of the photons to encode information, rather than the more commonly used polarization of light. During transmission Alice sends a photon of one of 16 predefined wavelengths (colors) and using a prism Bob detects the color and thus obtains 4 bits of information. The new approach quadruples the 1 bit per photon that is possible with current systems that rely on light polarization and could help increase the efficiency of quantum cryptography systems.

Re:Hmm

[ShanghaiBill]

Am I only one who finds the concept of using twisted beams of light to encode information overwhelmingly obvious?

You may have thought of it, but they did it. Ideas are a dime a dozen. Implementing them is harder.

Re:Telecom use?

[ArcadeMan]

American and Israeli researchers have used twisted vortex beams to transmit data at 2.5 terabits per second.

Egon Spengler: There's something very important I forgot to tell you.
Peter Venkman: What?
Spengler: Don't cross the streams.
Venkman: Why?
Spengler: It would be bad.
Venkman: I'm fuzzy on the whole good/bad thing. What do you mean, "bad"?
Spengler: Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
Ray Stantz: Total protonic reversal!
Venkman: Right. That's bad. Okay. All right. Important safety tip. Thanks, Egon.

Re:e and on a related topic the lameness filter su

[mrbester]

I'm still stuck reciting 2... being able to get to e is a pipe dream

DSN has been at 2.5 bits/photon for decades

[hyc]

The Deep Space Network has been transmitting 2.5 bits per photon for the past 30+ years. http://what-when-how.com/space...

How do these researchers not know that already?