Quantum Tunneling DEMO - Part 2

Quantum tunneling, something which can frighten one and inspire the other. It is possible to view this phenomenon with your own eyes! All you need is a prism-wedge complex and a laser. And let this happen to be what we are going to build!

With this guide, the focus is fully put on the complex since the laser was pre-built. As the name suggests, the complex is built up from different pieces: Two prisms, a wedge for in between the prisms and a clamping mechanism to hold it all together.

P.s. This is part of a bigger project which we all (Larissa Krab, Helen van Rooij and Mark Lemmens) have worked on together.

General:

• Lasercutter for the cutting
• A compatible program for the lasercutter, we used Inkscape
• Fully tansparant adhesive tape serving as a cover

Prisms:

• Plexiglass with a thickness of 10 mm, an area of 54x108 mm was used
• Polishing material for plexiglass
• Oil for sanding
• Sanding table
• Flat table for polishing
• Dishcloth

Wedge:

• Rolling papers
• Scissors

Clamping mechanism:

• Plywood with a thickness of 3 mm, an area of 61x10 mm was needed for the chosen design
• Some wood glue
• Two smaller clamps
• If needed:
• Some paper to put between this mechanism and the prisms to increase the pressure

For the prisms, a design has to be made first which is based on some calculations and assumptions. This design was immediately put into Inkscape in twofold to make sure that there were enough spares.

See '41-prisma's-versie2.svg' for the sizes and angles used.

With the Inkscape file now being finished, it is time to send it through to the lasercutter!

Now it is time for the cleaning process: the prisms need to be fully seethrough with an even surface which is thoroughly cleaned. This, as can be expected, is not the case when they've just come out of the lasercutter. After coming out of the lasercutter the prisms have imperfections on all sides from the laser. These can be removed by sanding the prisms on a sanding table, which can be seen in the first picture.

For the diagonal sides of the prism, considering they have to fit closely together for the quantum tunneling to occur, two prisms should be clamped together (as can be seen in the second picture) so their diagonal sides are sanded and polished together. This will make these sides more even, thus ensuring a good fit. It is smart to sand the orthogonal sides of all the prisms first, before clamping them. When clamped, the diagonal side should be sanded first until the imperfections of the laserprinter are gone.

The next part of the process is polishing the prisms; a flat table with a table cloth is used, and the polish is thoroughly shaken before some of it being put on the table cloth. The prisms should be rubbed over the polish on the flat table until the sides become clear (the diagonal sides should be polished first since they are still clamped). The difference between a sanded prism (bottom) and a sanded and polished prism (top) can be seen in the fourth figure.

NOTE: This process takes a fairly long time to complete, but it is really important that the prisms are properly polished and refined for quantum tunneling to be able to take place. And when moving the prisms, make sure to leave no fingerprints behind!

This step is a bit of an experimental 'test-and-repeat' case.

Given the fact the prisms have been refined by hand, the chance of irregularities and slight deviations from expectations are present. Because of this we will slowly build up layers of rolling papers between the prisms on one of the two sides, starting with just one and seeing when the width of the wedge is perfect for quantum tunneling to take place.

Now, to finalise the wedge, each paper has to be cut down to the height of the prisms so they don't form an obstacle for the cover we'll place later.

To ensure zero distance between the prisms on the opposite side of the wedge and a solid shape of the prism-wedge complex, a clamping mechanism has to be created.

As can be seen from the sketch and Inkscape picture, the clamp is build up from two pieces of wood which tightly envelope the outside of the prisms. These basically create an area for clamps to put over the prisms without damaging them.

NOTE: We recommend putting this small design in the same file as the prism holder (see instructable part 1).

And now also having finished the Inkscape design, the file for the clamping mechanism can be cut!

Everything is finally ready for grabs, let's put it all together and turn it into the complex we want!

If you haven't done this already in step 4, place the built-up wedge between the prisms on one outer side (see NOTE). After this is finished, place a piece of fully transparant adhesive tape over the newly created 'seam' between the prisms (see picture). If wished for, this tape can be brought further over the side of the wedge to cover this as well. The cover is needed to prevent any dust from collecting in the small space of the seam.

And lastly, the clamping mecanism has to be put together over the prisms. We used some wood glue to firmly secure the 4 parts together and create a place for the two clamps to press the prisms against each other.

Now we have made our prism-wedge complex where quantum tunneling can take place!

Handy tip: If the clamp isn't tight enough, some small pieces of paper can be put between the clamp and the prisms.

Another handy tip: You can use the pictures as guides for the building-part.

NOTE: For us the prisms happened to have a perfect structure themselves after the polishing and sanding where there was barely any tunneling on one side and almost full tunneling on the other. Because of this, the decision was made to not put in a wedge.