Quantum computing is a technology that uses the power of quantum mechanics to process information. It has the potential to solve complex problems that are difficult or even impossible to solve with classical computers. The most powerful quantum computers today are owned by Google, IBM, Intel, Microsoft, and Rigetti Computing. These companies are leading the way in quantum computing research and development.

Quantum computers use quantum bits, or qubits, instead of traditional bits of information like classical computers. Qubits can store more information than traditional bits, and they can exist in **both a 1 and 0 state at the same time.** This phenomenon is called superposition, and it enables quantum computers to process vast amounts of information quickly and efficiently. Additionally, quantum computers can take advantage of a phenomenon called **entanglement**, in which two qubits can be linked together in such a way that a change in one qubit affects the other. This enables quantum computers to process large amounts of data simultaneously, potentially leading to faster and more efficient computing.

Entanglement is a phenomenon in which two particles are linked together in such a way that a change in one particle affects the other, even if they are separated by large distances. This phenomenon is exploited in quantum computing, as it allows qubits to be connected in such a way that they can process large amounts of data simultaneously. For example, in a classical computer, two bits can only be either a 0 or a 1, but in a quantum computer, two qubits can both be a 0 and a 1 at the same time due to entanglement. This enables quantum computers to process vast amounts of information quickly and efficiently.

Entanglement of subatomic particle decays into an entangled pair of other particles. The decay events obey the various **conservation laws**, and as a result, the measurement outcomes of one daughter particle must be highly correlated with the measurement outcomes of the other daughter particle (so that the total momenta, angular momenta, energy, and so forth remains about the same before and after this process).

For instance, a spin-zero particle could decay into a pair of spin-1/2 particles. Since the total spin before and after this decay must be zero (conservation of angular momentum), whenever the first particle is measured to be spin up on some axis, the other, when measured on the same axis, is always found to be spin down. (This is called the spin anti-correlated case; and if the prior probabilities for measuring each spin are equal, the pair is said to be in the singlet state.)