Technology Today - Home
[an error occurred while processing this directive]
Connecting the Quantum Dots

The process of coming up with a good idea can be long; building a prototype and acquiring funding can have many facets. Most pursuits of technology breakthroughs are dry holes. But sometimes an examination of the pile of dirt next to the hole leads you in a new direction that eventually creates real value.

Connecting the Dots From Concept to Customer
In the 1990s, Raytheon was completing a project that studied the possibility of constructing a massively parallel image processor chip for use in kinetic kill vehicles. The logic circuits at the heart of this superprocessor would be composed of quantum dot logic gates. These tiny logic elements are about 10 nanometers in each dimension and ideally suited to packing into the three-dimensional logic arrays needed to make the concept work. Since the quantum-coupled image processor (QuIP) project was only a design effort, when it ended it was judged a complete success. The component was never built, but the effort resulted in a lot of creative thinking and a few patents.

One question arose while pondering the quantum content of the processor. "What would happen if this 'Rubik's Cube®' of quantum dots blew up at impact and scattered the quantum dot cells all over outer space?" Besides wasting a lot of perfectly good quantum dots (about 10 trillion), there would in fact be an optical side effect. The ambient solar energy, rich in ultraviolet radiation, would optically pump the quantum dots and they would re-emit this absorbed energy in the visible and infrared region of the spectrum. In fact, the plume of debris would create a brilliant fluorescent cloud of broadband light that could emit many watts of optical power. So the ambitious but successful super-processor would disassemble into a nebula of brilliant light some hundred miles above the earth.

Fast forward to today. In 2007 Raytheon held the first Grand Challenge workshop that united people from across the company to stimulate new ideas and concepts. One of the challenges included the need to develop ways to counter enemy air defenses. One idea that emerged was the notion of an electronic, fog-like material that could be dispersed into a giant plume and used to degrade the ability of enemy radar to detect aircraft. The concept is similar to the old idea of deploying clouds of metallic chaff that would reflect radar signals and generate false echoes. This "chaff" would be different — scavenging energy from sunlight and enemy radar and using this energy to effectively shield incoming aircraft from detection. The idea evolved into a concept for environmentally powered electronic mist.

A connection with the cloud of optically fluorescent quantum dots from the 1990s was made. The particles in this fog needed to be tiny but very energy efficient, and be able to scavenge power from very lowdensity sources. After analyzing the concept, it became clear that the ideal device to absorb ambient energy and disrupt the radar was indeed a variation of the quantum dot used in the conceptual QuIP super-processor. A single quantum tunnel diode could be used as an energy harvester and allow for remote on/off control. Importantly, this functionality could be packed into microelectronic chips small enough to be used as the pigment in a fog generator.

To prove out the notional idea, some archived samples of quantum tunnel diodes were tested in the Raytheon Space and Airborne Systems APC Innovation Center using an in-place probe station, light source, signal generator, and spectrum analyzer. As conjectured, injecting energy into the diode generated a DC voltage that charged up an on-chip capacitor. When this power was removed, the voltage dropped to a level that caused the diode to spontaneously oscillate. This experiment provided the confidence needed to engage with potential customers, one of whom was keenly interested.

Playing in the Innovation Sandbox
This project would have lain dormant if there hadn't been an innovation lab with equipment available to go in and test the concept. Resonant tunneling diodes (RTDs) that were more than 10 years old were used to show that the concept worked. These parts had been sitting in a dry-box in the innovation lab for a long time and by most accounts should have been thrown away. The RTDs were never designed to be used this way, but they solved an important problem in an unintended fashion. There are many more technological gems populating Raytheon's innovation labs just waiting for someone to find a new way of using them.

It is important to note that none of these ideas arose in response to a well-defined customer requirement, but rather fell out of free thinking about how to solve multiple big-picture problems. With this in mind, engineers should try to frame their own problems and not wait for someone to define the problem or the solution space.

One person's kinetic kill vehicle seeker is another person's can of electronic fog.

Brandon Pillans

Rubik's Cube is a registered trademark of Seven Town Ltd.