  Quantum entanglement is a central concept of quantum theory for multiple
particles. Entanglement played an important role in the development of the
foundations of the theory and makes possible modern applications in quantum
information technology. As part of the QuVis Quantum Mechanics Visualization
Project, we developed an interactive simulation "Entanglement: The nature of
quantum correlations" using two-particle entangled spin states. We investigated
student understanding of entanglement at the introductory and advanced
undergraduate levels by collecting student activity and post-test responses
using two versions of the simulation and carrying out a small number of student
interviews. Common incorrect ideas found include statements that all entangled
states must be maximally entangled (i.e. show perfect correlations or
anticorrelations along all common measurement axes), that the spins of
particles in a product state must have definite values (cannot be in a
superposition state with respect to spin) and difficulty factorizing product
states. Outcomes from this work will inform further development of the QuVis
Entanglement simulation.
