  Quantum mechanics provides a disembodied way to transfer quantum information
from one quantum object to another. In theory, this quantum information
transfer can occur between quantum objects of any dimension, yet the reported
experiments of quantum information transfer to date have mainly focused on the
cases where the quantum objects have the same dimension. Here we theoretically
propose and experimentally demonstrate a scheme for quantum information
transfer between quantum objects of different dimensions.By using an optical
qubit-ququart entangling gate, we observe the transfer of quantum information
between two photons with different dimensions, including the flow of quantum
information from a four-dimensional photon to a two-dimensional photon and vice
versa.The fidelities of the quantum information transfer range from 0.700 to
0.917, all above the classical limit of 2/3. Our work sheds light on a new
direction for quantum information transfer and demonstrates our ability to
implement entangling operations beyond two-level quantum systems.
