Abstract
Two photons can simultaneously share entanglement between several degrees of freedom such as polarization, energy-time, spatial mode and orbital angular momentum. This resource is known as hyperentanglement, and it has been shown to be an important tool for optical quantum information processing. Here we demonstrate the quantum storage and retrieval of photonic hyperentanglement in a solid-state quantum memory. A pair of photons entangled in polarization and energy-time is generated such that one photon is stored in the quantum memory, while the other photon has a telecommunication wavelength suitable for transmission in optical fibre. We measured violations of a Clauser-Horne-Shimony-Holt (CHSH) Bell inequality for each degree of freedom, independently of the other one, which proves the successful storage and retrieval of the two bits of entanglement shared by the photons. Our scheme is compatible with long-distance quantum communication in optical fibre, and is in particular suitable for linear-optical entanglement purification for quantum repeaters.
Highlights
Quantum entanglement is an essential resource for quantum information processing, and in particular for quantum communication and for quantum computing
The signal and idler are separated by a dichroic mirror (DM), and the modes are recombined at a polarizing beam splitters (PBSs)
We have shown the storage of energy-time and polarization hyperentanglement in a solid-state quantum memory
Summary
Quantum entanglement is an essential resource for quantum information processing, and in particular for quantum communication and for quantum computing. Hyperentanglement has applications in optical tests of nonlocality [12], as well as linear-optical quantum computing [13,14] and the generation of multi-qubit entangled states using a smaller number of photons [15] In this context, light–matter hyperentanglement was demonstrated using spatial and polarization DOFs, and was used in a demonstration of one-way quantum computing [16]. This could play an important role in the context of long-distance quantum communication with quantum repeaters, where purification can be used to increase the rate at which entanglement is distributed [18,19] This is possible only if the DOFs in which the hyperentanglement is coded are suitable for long-distance transmission, e.g., in optical fiber. The requirements that arise for quantum repeaters is to have quantum memories that can efficiently store both DOFs, combined with the possibility of efficiently distributing entanglement over long distances in optical fiber
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