System Bits: May 20

Re-routing noise away from measurement
Today, we are capable of measuring the position of an object with unprecedented accuracy, but quantum physics and the Heisenberg uncertainty principle place fundamental limits on our ability to measure. Noise that arises as a result of the quantum nature of the fields used to make those measurements imposes what is called the “standard quantum limit,” which influences both the ultrasensitive measurements in nanoscale devices and the kilometer-scale gravitational wave detector at LIGO. Because of this troublesome background noise, we can never know an object’s exact location, but a recent study by Caltech research provides a solution for rerouting some of that noise away from the measurement.

The researchers noted that if you want to know where something is, you have to scatter something off of it. For example, if you shine light at an object, the photons that scatter off provide information about the object. But the photons don’t all hit and scatter at the same time, and the random pattern of scattering creates quantum fluctuations—that is, noise. If more light is shone, there is increased sensitivity but there is also more noise. In this work, they were looking for a way to beat the uncertainty principle—to increase sensitivity but not noise.

Once the researchers had a reliable mechanism for detecting the forces generated by the quantum fluctuations of microwaves on a macroscopic object, they said they could modify their electronic resonator, mechanical device, and mathematical approach to exclude the noise of the position and motion of the vibrating metal plates from their measurement.

The experiment shows that a) the noise is present and can be picked up by a detector, and b) it can be pushed to someplace that won’t affect the measurement – it’s a way of tricking the uncertainty principle so that the sensitivity of a detector can be dialed up without increasing the noise.

The tiny aluminum device—only 40 microns long and 100 nanometers thick—in which Caltech researchers observed the quantum noise from microwaves. (Source: Caltech)

This line of research could one day lead to the observation of quantum mechanical effects in much larger mechanical structures, which could allow the demonstration of strange quantum mechanical properties like superposition and entanglement in large objects—for example, allowing a macroscopic object to exist in two places at once.

Wirelessly powering implanted medical devices
A Stanford electrical engineer has invented a way to wirelessly transfer power deep inside the body and then use this power to run tiny electronic medical gadgets such as pacemakers, nerve stimulators or new sensors and devices yet to be developed.

The discoveries culminate years of efforts by Ada Poon, assistant professor of electrical engineering at Stanford, to eliminate the bulky batteries and clumsy recharging systems that prevent medical devices from being more widely used.

The technology could provide a path toward a new type of medicine that allows physicians to treat diseases with electronics rather than drugs.

The team built an electronic device smaller than a grain of rice that acts as a pacemaker. It can be powered or recharged wirelessly by holding a power source about the size of a credit card above the device, outside the body.

The central discovery is an engineering breakthrough that creates a new type of wireless power transfer – using roughly the same power as a cell phone – that can safely penetrate deep inside the body. As Poon writes, an independent laboratory that tests cell phones found that her system fell well below the danger exposure levels for human safety.

Poon believes this discovery will spawn a new generation of programmable microimplants – sensors to monitor vital functions deep inside the body; electrostimulators to change neural signals in the brain; and drug delivery systems to apply medicines directly to affected areas.

A batteryless electrostimulator next to medicinal pills for size comparison. The new powering method allows the device to be wirelessly powered deep inside the body, in locations such as the heart or brain. (Source: Stanford)