Fiber-optic links and the lasers that send data across them are nothing new. Both have been used in data communication for literally decades, now, and various technologies have improved the utility of both over that time. While they are generally used for longer-haul connections between routing and switching equipment within a communications network – as opposed to between the user-endpoints like computers and phones and the “first hop” connection they use – there’s been efforts at bringing that technology closer to the end user. Light is far faster than electrical pulses which would open the door to much fast computing technology. There are also advantages to using light over electricity in security terms because it’s much harder to eavesdrop on an optical link than a traditional wired one.
One of the efforts that’s been underway involves the use of quantum mechanics to encode and encrypt data. Theoretically, it becomes possible to inscribe data within the quantum characteristics of a single photon of light. Rather than encode the data in a series of “on’s” and “off’s” of a laser shining down a fiber optic, you can literally send complex data in a stream of photons, each one carrying distinct data instead of being just 1 bit of an information flow. The speed of transmittal would increase phenomenally. Such a technology would also raise security concerns.
There are ways to detect an unauthorized tap into an electrical circuit. Current laser transceivers have an operating limitation that makes it far more difficult to replicate that kind of detection. When they fire, they emit several photons at the same time, making it possible that someone can receive the information being sent and do so in such a way that the authorized recipient would never know. The issue has made it critical to find a way to make a photon gun that can actually fire only 1 photon at a time. Via Instapundit I read this fascinating article over at the technology review blog, published by MIT.
One of the significant weaknesses of current quantum cryptographic systems is the finite possibility that today’s lasers emit photons in bunches rather than one at a time. When this happens, an eavesdropper can use these extra photons to extract information about the data being transmitted.
So there’s no shortage of interest in developing photon guns that emit single photons and indeed various groups have made significant progress towards this.
Against this background, Michael Fortsch at the Max Planck Institute for the Science of Light in Erlangen, Germany, and a few pals today say they’ve made a significant breakthrough. These guys reckon they’ve built a photon emitter with a range of properties that make it far more flexible, efficient and useful than any before–a kind of photon supergun.
This “Quantum Rainbow Color Gun” manages to fire 2 entangled photons at a time, but photons with different properties. The one of them is being refered to as a photon herald, definitively announcing that the gun has fired and that a 2nd photon is on the way. The 2nd one carries the encoded data. This effectively removes all doubt as to whether the gun is leaking data. It’s an important step in the development of the next generation of computing devices.