We’ve covered quantum information, and we’ve covered circuits, so it feels right to combine the two.

Quantum circuits (the topic of my science fair project!) are used to aid in quantum systems designed primarily for computational studies. In a quantum circuit, you will of course find qubits, but you may also encounter gates or measurement sites! A gate helps create entanglement, allowing for more information to be contained in a quantum system. However, entanglement saturates at a value dependent on the number of qubits in the system (around n/2 * ln(2) for a system with n qubits and no measurement).

Measurement acts as a kind of anti-gate – it reduces the entanglement in a system, because whenever we measure the state of a qubit, we collapse its superposition, reverting the qubit into a classical bit. At a measurement site, the probability that a measurement actually occurs can be given as p; as p increases, the total entanglement of the system decreases.

That is all I have to share today about quantum circuits! I forgot to attach the solution to the circuits problem to the last post, so here it is:

Original problem: “We have two resistors in series, with resistance 2 Ohms and 4 Ohms, respectively. These resistors are in parallel with another resistor of 6 Ohms. Calculate the current of the circuit if these resistors are in a closed loop circuit with a battery of voltage 9 V.”

Solution: First, we take the resistors in series and calculate the total resistance of that branch (2+4 = 6 ohms). Next, we take this resistance and calculate the total resistance in the circuit via calculations for parallel resistors; 1/(1/6 + 1/6) = 1/(1/3) = 3 ohms. Lastly, we apply Ohm’s law V = I*R to get I = V/R = 9/3 = 3 Amperes.