Unanswered QuestionsEntanglement, Teleportation, and Quantum Computing |
What is a qubit? |
Qubit is short for quantum bit, the basic piece of information for a quantum computer. A qubit can be the state of an atom, ion, photon, or an electron. As was the case of the polarization of the two gammas, the qubit doesn’t have a value of 0 or 1, but is in a state that is a superposition of 0 and 1, so it can have any value between those two numbers. If you try to measure the value of the qubit you will get either 0 or 1, so it will act like a bit in a normal computer. The trick is to use one of two entangled photons (or atoms) to determine the qubit’s state without collapsing it into either 0 or 1.
Quantum computers are by nature parallel machines that can work on many problems at once. At this time computers with 12 qubits have been demonstrated, so there is a long way to go before such a device is practical. Still, progress is being made. A company has demonstrated a way of using the kind of chip lasers used in CD players to create entangled photons, greatly reducing the size, complexity, and cost of a quantum computer.