Quantum Entanglement Explained

Ray LaPierre

There exist multiphoton states that cannot be expressed as a product of individual photon states. These states are called entangled states. Einstein used hidden variables in an attempt to explain the probabilities of quantum mechanics. John Bell proposed a test, using entangled states, showing that quantum mechanics cannot be explained by hidden variables.

Alice Flarend, Bob Hilborn

Abstract Quantum state entanglement is a crucial ingredient in many quantum algorithms. This chapter introduces the description of multiqubit quantum systems and then explains what it means to say the state of that system is entangled. If the quantum state of the system is an entangled state, none of the constituents of the system are described by their own individual states. For a two-qubit entangled state, measurements on one of the qubits apparently affects the measurement results of the other even though the two qubits may be far apart. Entanglement is explained using both joint and conditional probabilities of measurement results.

MB

Dean L. Mamas

Bell test experimental results can be classically explained as simply a trivial geometric effect, without any need to evoke any quantum phenomena such as entanglement. There is no instantaneous action-at-a-distance.

Garay, Linda Bertel