Week 20 - my notes

Week 20 - Quantum Computing & Beyond

Superconduction was discovered in 1911, when Kammerligh Onnes cooled mercury down to 3K and it conducted electricity with no resistance
However, a full theory of superconductivity was only created in 1957 (BCS theory) – by means of quantum mechanics
SQUIDs (superconducting quantum interference device) are sensible to tiny magnetic field produced by our brain – this was quantum 1.0
We’ve gotten to quantum 2.0 when we improved those devices and were able to visualize quantum properties in these circuits

In quantum 1.0, we don’t need quantum to understand what is happening, but it is there

A consequence of wave-particle duality
The more exactly we can point out the position, the less exact we can express the wavelength
It is also applied to energy and time
We engineer around this fundamental idea!

Particles end up in places that they shouldn’t be allowed classicaly, like crossing a wall
That’s how we can see through a window, or hear that lousy neighbour!
Tunneling is easiest when the barrier is thin
Fun fact: Quantum tunneling makes the stars shine – The energy limit required for two atoms to fuse is like a barrier
Quantum tunneling is also used in sensors: Scanning tunneling microscope (STM)
In STM, we move a very sharp tip over the sample we want to image, it measures how many electrons are tunneling and gives you a picture of this sample

Quantum tunneling in the sun URL: https://www.youtube.com/watch?v=gS1dpowPlE8 The Nobel Laureate vs the Graduate Student URL: https://physicstoday.scitation.org/doi/10.1063/1.1397394 Description: History of the Josephson effect, the key enabling discovery behind superconducting qubits Real-world Oracles URL: https://arxiv.org/pdf/quant-ph/9911082.pdf URL: https://arxiv.org/pdf/quant-ph/9607014.pdf