Quantum Tunneling and Its Applications

Quantum Tunneling

And its Applications

But First... What does Quantum Tunneling Require?

The Quantum Refrigerator

It's like blowing on a hot cup of coffee!

How can quantum tunneling be used to cool something down?

What is this?

• The world's most recent innovation in quantum refrigeration
• Using quantum tunneling, it is able to cool objects as large as this 2.5cm square copper stage
• The object to be cooled is wrapped in a unique membrane

• A thin, insulating (nonconducting) barrier to tunnel through that would be classically impermeable
• An energetic, quantum particle (electron, photon)
• A conductive surface on both sides of the barrier, one the particle to leave from and the other to tunnel toward

We're left with cold electrons!

But how cold is "cold"?

• This 2.5cm square copper stage was able to be cooled from 290mK to 256mK (~10%) in 18 hours using only 48 quantum-tunneling junctions (Wogan).
• But this is nothing close to the ultracold temperature necessary for Bose-Einstein Condensation or other physics phenomena, which is usually within the nanoKelvin range.

So then why is this so important/interesting?

Because of the size of the target that can be cooled! This 2.5cm square stage (which is 0.3cm thick) is approximately 16.8g (at room temperature). Meaning it contains over 1.5x10^23 atoms, as opposed to the few million atoms that are typically cooled for Bose-Einstein Condensation!

Quantum Tunneling

Applications

Quantum Tunneling... In Your Nose!?

How does your nose recognize smells?

Smell (Chemical)

Enters Nose

What if two smells are similar?

Cells in Nose

Identified by Chemoreceptors on Cell Surface

Quantum tunneling has unique features that allow it to be used in a variety of applications:

• Scanning Tunneling Microscope
• Quantum Refrigeration
• Touch Screens
• Artificial Skin
• Flash Drives
• And even your own nose!

By Running a Current Into the Molecule!

• Our chemoreceptors can run a current into the incoming smell molecules to make them vibrate!
• The bonds found in the smell molecule give it a unique vibration
• This means each chemoreceptor can identify multiple, similarly-shaped smell molecules

Frequently, this requires using quantum tunneling!

From the Chemoreceptor

to the Smell Molecule

It has been shown that fruit flies can distinguish between molecules that are only different in the number of neutrons in the hydrogen atoms!

• Electrons travel to the smell molecule through the small, insulating gap between the molecule and the chemoreceptor
• This creates a current in the molecule, allowing for it to be identified!

Thanks!

Any Questions?

References:

Dillow, Clay. “Your Nose Could Use Quantum Tunneling to Distinguish Between Similar Molecules.” Popular Science 15 Feb. 2011. Web. 16 Apr. 2013. <http://www.popsci.com/science/article/2011-02/your-nose-could-leverage-quantum-tools-distinguish-between-similar-molecules>

Grifantini, Kristina. “Artificial Skin will use Quantum Tunneling.” MIT Technology Review 22 February 2010. Web. 17 Apr. 2013. <http://www.technologyreview.com/view/417583/artificial-skin-will-use-quantum-tunneling/>

Mullin, William. “Quantum Waves and Particles, Weirdness Notes #3.” University of Massachusetts Amherst Physics, Spring 2013. Moodle. UMass Amherst Physics. PDF file. 15 Apr. 2013.

Palmer, Jason. “Quantum trick for pressure-sensitive mobile devices.” BBC News. BBC News, 9 Feb. 2010. Web. 15 Apr. 2013. <http://news.bbc.co.uk/2/hi/science/nature/8504373.stm>

“Tunneling Applications.” Massachusetts Institute of Technology Open Courseware, Spring 2011. Electromagnetic Energy: From Motors to Lasters. MIT Open Courseware. PDF file. 15 Apr. 2013. <http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-007-electromagnetic-energy-from-motors-to-lasers-spring-2011/lecture-notes/MIT6_007S11_lec43.pdf>

Wogan, Tim. “Quantum refrigerator is efficient and reusable.” Institute of Physics, Physics World 12 Mar. 2013. Web. 16 Apr. 2013. <http://physicsworld.com/cws/article/news/2013/mar/12/quantum-refrigerator-is-efficient-and-reusable>

"Quantum Tunneling." Youtube 20 Aug. 2012. Web. 19 Apr. 2013. <

Touch Screens and Artificial Skin!

We can use quantum tunneling to sense pressure!

• Don't forget, one of the ways that quantum tunneling can be made easier is by providing a smaller insulating gap!
• Next generation touch screens are incorporating this into their design, allowing the screens to sense pressure, adding a third dimension to how we use touch screens
• The more pressure applied to the outer layer, the more deformed the screen will be, causing the insulating gap to decrease in size, and the chance of quantum tunneling to increase
• We can even use this in artificial skin!