Similar to a computer bit, Qubits are a unit of measurement that represent two entangled atoms or particles operating under the rule-set of quantum physics. You can entangle atoms and particles by shooting them
At a certain level of magnification atoms and particles begin to operate differently. Instead of remaining in one place, they assume a “probability wave” of superposed states. When you observe one of two entangled photons for example, it will appear to spin either up or down. Then when you observe the other photon, it will spin in the opposite direction, however – at a perfect distance they assume both states at once.
What that means is that each Qubit is capable of holding a superposition of these two possible states as well as everything in between. This feature increases the informational complexity of qubits to supersede that of ordinary bits which can only encode a single state: 1 or 2 respectively. Since photons are 3 dimensional, you can also encode any coordinate on their spherical surface – further increasing complexity.
Qubits are programmed with light. By shooting electromagnetic radiation at an entangled pair from different angles and distances you create an array of possible coordinates that operate as subtleties in “code”. This code can then be read by shooting microwaves in to a resonant cavity containing the atom/particle.
Since direct observation and measurement ruins the data, scientists have to be sneaky about it. So they shoot microwaves in to the resonant cavity in order to see how they “bounce off” of the atom/particle. Using this method they can determine how the qubit is entangled, without collapsing the superposition of possible states.