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## Time Cloak for Digital Logic?

Time cloaking has been demonstrated using light waves. What might that mean for particle models, as in IC applications?

Here’s a mental exercise for circuit designers. It evolves the application of a time cloak to electron particles in a digital circuit. But first, a bit of background information might help.

Temporal cloaking allows researchers to change the perception of time. I reported on this amazing experiment last year.  (see, “Time Travel is Out: Stopping Time is In”)

A team of physicists at Cornell University created a time gap by briefly bending the speed of light around an event – not an object. The experiment involved changing the speeds of different light waves. The gap lasted only 50 trillionths of a second. A scaled up version of this demonstration shows an art thief walking into a museum to steal a painting without setting off laser beam alarms or even showing up on surveillance cameras.

The time gap was demonstrated through the use of light waves. But quantum phenomena can be modeled as either waves or particles. How would a time cloak work in a particle representation?

The key to the Cornell experiment was the changing speed of different wavelengths of light. A corresponding particle representation might involve changing the speed of  electron “particles.” But electron motion is at best a statistical measurement, if one applies Heisenberg’s uncertain prediction for momentum and position.

Before exploring this challenge further, one might wonder as to the practical use of time cloaks. What could they be used for? In a circuit, the faster flow of electrons might cause an unintended output from a given set of logic functions. This assumes that the transistors could switch fast enough to operate with higher speed particles. Silicon transistors may not work, but there is an alternative.

Recent reports from IBM show that graphene switches can reach speeds of 100 gigahertz–meaning they can switch on and off 100 billion times each second, about 10 times as fast as the speediest silicon transistors. That should be fast enough for our theoretical time cloak particle experiment.

The next challenge is to create a circuit with two logic flows – one for normal speed and another for faster electrons. The faster electrons would complete their logic functions before the “normal” logic was finished. To what end, you ask? Perhaps to completely disable the rest of the circuit? This might be a problem if the circuit was part of the communication system for a fighter jet.

Of course this scenario is not that new. Many have suggested that RTL could be added to circuits just prior to fabrication in a foreign foundry to achieve the same dangerous result. (see, “Foreign Fabs and Killer Apps”) But with a time cloak, the “hidden” circuit would not be hidden at all or even added in secret. It would be there for all to see but completely undetectable except when the “time cloaked” faster electrons were activated.

Unfortunately, this scenario of a particle-based, digital time cloak is fatally flawed. An astute first year student in engineering would be able to spot the flaw in short order. Can you?

I’ll post my answer in the next blog.