Discrete, Tunable Color Entanglement

Author(s): S. Ramelow, L. Ratschbacher, A. Fedrizzi, N. K. Langford, A. Zeilinger

Journal: Physical Review Letters

Volume: 103

Page(s): 25360

Year: 2009

DOI Number: 10.1103/PhysRevLett.103.253601

Link: Link to publication


Although frequency multiplexing of information has revolutionized the field of classical communications, the color degree of freedom (DOF) has been used relatively little for quantum applications. We experimentally demonstrate a new hybrid quantum gate that transfers polarization entanglement of non-degenerate photons onto the color DOF. We create, for the first time, high quality, discretely color-entangled states (with energy bandgap up to 8.4 THz) without any filtering or postselection, and unambiguously verify and quantify the amount of entanglement (tangle, 0.611$\pm$0.009) by reconstructing a restricted density matrix; we generate a range of maximally entangled states, including a set of mutually unbiased bases for an encoded qubit space. The technique can be generalized to transfer polarization entanglement onto other photonic DOFs, like orbital angular momentum.

Note: http://arxiv.org/abs/0904.4916

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