- Quantum physics is the study of quantum phenomena
- A ‘quantum’ being the study at smallest possible scale (discrete not continuous measurement)
- A quantum bit (qubit) can exist in superposition of 0 and 1 to simplify, it is a linear combination of 0 and 1, through measurement of spin
- Q-bits use complex numbers to point to a position in 2 dimensional vector space
- We talk about instability as decoherence
Sending the Message §
- Knowing that a quantum particle (a photon in this case) has spin, we take advantage of quantum filters
- Photons are passed through one of these filters (at random)
- They are chosen at random and as they pass through, the photon is changed to a certain spin (rotation)
Receiving the Message §
- At the receiving end, we use two filters (rectilinear or diagonal) at random and measure the outcome as a 0 or 1
- Quantum physics (Heisenberg) states that we can only measure the spin by passing it through a filter
- If the correct filter is used, we correct measure a 0 or 1
- If you use the wrong filter, you change the particle and will misread it.
