Signal Processing - January 2017 - 10

Yousif Kelaita/stanford universitY

Figure 1. An enlarged artist's rendering showing a gallium arsenide chip. The pink vector (at the
bottom) depicts "classical" or laser light entering the chip. The blue structure in the center is indium
arsenide. This material acts like a special filter that allows classical light to pass through while also
generating quantum light (shown in blue) that provides a secure way to transmit data.

The biggest technical challenge still
facing the researchers is scaling the
optical light devices down to a size that
will allow for integration into quantum
networks. "We are working toward
demonstrating adapting this technique
in an on-chip quantum network, where
light propagates down a waveguide as
opposed to through free-space," Fischer comments.
Using state-of-the-art nanofabrication
technology, the team is currently engineering its first quantum light devices.

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phase-locking of the signal and oscillator fields, which is challenging to
achieve with light compared to radio frequency fields. "This is challenging with
light, because the wavelength is much
smaller-on the order of microns as opposed to meters-which then necessarily requires greater precision," Fischer
says. "Therefore, our advance was to
find a device structure that generated
both the local oscillator field and the
quantum signal, which were then inherently aligned to one another."

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Figure 2. A network of sensors observing a field. Ioannis Schizas, an assistant professor of electrical
engineering at the University of Texas at Arlington, is developing a sensing environment that would use
multiple simple devices to collect and process data that currently requires the power of a supercomputer.
(Photo courtesy of the University of Texas at Arlington.)

IEEE Signal Processing Magazine

January 2017

Building such devices with the required
low tolerances challenges even the most
advanced fabrication techniques. "Our
interferometer's largest critical dimension
is microns and smallest critical dimension is nanometers," Fischer says.
Creating a practical and cost-effective approach to integrating optical light
devices into standard complementary
metal-oxide-semiconductor (CMO)
fabrication processes is yet another challenge facing the researchers. "Therefore,
we're also investigating CMOS-compatible material platforms that can support
our technology," Fischer says.
As the researchers turn their attention toward developing a functional prototype, commercial applications exist
as only a distant possibility. "Not yet,"
Fischer says. "We first need to demonstrate that our device works in a waveguide-based system."

Simpler sensor networks
Ioannis Schizas, an assistant professor
of electrical engineering at the University of Texas at Arlington, is developing
a sensing environment that would use
multiple simple devices to collect and
process data that currently requires the
power of a supercomputer (Figure 2).
"Sensors provide huge amounts of data,
but using and applying the data they collect requires a very powerful computer,"
Schizas says. "I hope to eliminate that
need through simplicity of design."
As he creates the new sensing environment, Schizas is using several different types of commonly available
sensors to collaborate with each other
and gather various types of data that
can be either sorted or ignored. He
hopes to eliminate the need for supercomputing by using optimization techniques to determine the best placement
of sensors, including thermometers,
accelerometers, pressure sensors, and
acoustic sensors equipped with digital
signal processors (DSPs) and wireless
communications support. Schizas says
his research relies on the development
of novel signal processing techniques.
"It is fair to say this is a signal processing research project," he states.
Schizas says his research is currently
focused on the development of general

Table of Contents for the Digital Edition of Signal Processing - January 2017