# Are there any practical applications of the uncertainty principle

I believe GPS works because of extremely small time differences between the satellites. Because of how small the time differences are, it needs to take into account gravity's effect on time. Although gravity warping time seems very far fetched in normal life, there are practical applications that we use every day that would not work if we did not know about it.

I was curious if the same applies to the uncertainty principle. Is there something that I use everyday that wouldn't work if we didn't know about the uncertainty principle? Or is it just crazy quantum mechanics?

• This question (v2) seems like a list question. May 6, 2016 at 5:45

I'm not sure about how the uncertainty principle applies to everyday electronics, but one thing that wouldn't work without it is an electron microscope. Scanning tunneling electron microscopes are used to see things which are too small to observe with light, such as atoms.

The process they use is actually called quantum tunneling. basically, a negative charge is applied to a very fine, conductive tip, and the tip is positioned extremely closely to the surface you want to examine. Since the tip and surface don't actually touch, the charge can't transfer. However, due to the uncertainty principle, we can't really know that precisely zero electrons will transfer to the surface, and in reality there is a small probability that the charge will seemingly defy the laws of physics and "tunnel" across the gap into the surface. The probability that this happens decreases with distance, so the closer a part of the surface (such as an atom) is to the tip, the more electrons will tunnel through to it.

This only happens on a very small scale. It's theoretically possible for a basketball to run into a wall, and instead of bouncing off, tunneling through to the other side. But the more macroscopic an object is, the lower the probability of that happening.

• Note that the scanning tunneling electron microscope is a different critter than the plain old scanning electron microscope. The device you describe is the former. Jul 7, 2011 at 14:13
• Can a probability of a basketball "tunneling" through a wall ever reach exactly 0? If not, does this mean: The Moon can "tunnel" through the Earth (with insanely small probability)? Feb 27, 2012 at 8:46
• @sabiland Sure. But that probability is so small it's not even worth considering, i.e. it wouldn't happen if you watched it for the lifetime of a thousand universes. Feb 27, 2012 at 18:59

The uncertainty principle ascribed to the phenomenon of quantum-level noise, is the principle used in hardware random number generators, which are sometimes used for strong data encryption. These devices can generate numbers that are genuinely random by, for example, detecting noise in light sensitive diodes (the photoelectric effect) and other quantum phenomena.

The Data transfer in the USB flash drives uses the principle of quantum tunneling & hence the uncertainty principle.

• Every electronic device which uses a transistor relies on this effect. Feb 24, 2012 at 21:05

One application is a result of a general class of phenomena named "squeezed coherent states"

In physics, a squeezed coherent state is any state of the quantum mechanical Hilbert space such that the uncertainty principle is saturated. That is, the product of the corresponding two operators takes on its minimum value ...

Squeezed states of the light field can be used to enhance precision measurements. For example, phase-squeezed light can improve the phase read out of interferometric measurements (see for example gravitational waves). Amplitude-squeezed light can improve the readout of very weak spectroscopic signals.

Spin squeezed states of atoms can be used to improve the precision of atom clocks. This is an important problem in atomic clocks and other sensors that use small ensembles of cold atoms where the quantum projection noise represents a fundamental limitation to the precision of the sensor.

The Heisenberg Uncertainty Principle is in the very core of quantum mechanics. It is an easy to apply limiting envelope to variables, based on the fact that conjugate variables have to obey quantum mechanical commutator relations, the HUP is derived from them.

Commutator relations are at the basic core of quantum mechanics. In this sense, all quantum mechanical applications depend on the Heisenberg uncertainty principle because the applications are solutions of specific quantum mechanical equations with boundary conditions. From transistors to nanotechnology, the HUP underlies everything.