Abstract
Entanglement in multiple degrees of freedom has many benefits over entanglement in a single one. The former enables quantum communication with higher channel capacity and more efficient quantum information processing and is compatible with diverse quantum networks. Establishing multi-degree-of-freedom entangled memories is not only vital for high-capacity quantum communication and computing, but also promising for enhanced violations of nonlocality in quantum systems. However, there have been yet no reports of the experimental realization of multi-degree-of-freedom entangled memories. Here we experimentally established hyper- and hybrid entanglement in multiple degrees of freedom, including path (K-vector) and orbital angular momentum, between two separated atomic ensembles by using quantum storage. The results are promising for achieving quantum communication and computing with many degrees of freedom.
Highlights
Entanglement in multiple degrees of freedom has many benefits over entanglement in a single one
Entanglement in multiple degree of freedom (DOF) can exploit the advantages of different DOFs; for example, photons entangled in the polarization or time-bin DOF can be efficiently transmitted through an optical fibre, whereas photons encoded in orbital angular momentum (OAM) space offer improved channel capacity in the fields of both classical[22] and quantum[23,24] information
When we shut off the coupling light, the Signal 1 photon is stored in magnetooptical trap (MOT) B as an atomic spin wave, establishing hyperentanglement between the spin waves of the two atomic ensembles
Summary
Entanglement in multiple degrees of freedom has many benefits over entanglement in a single one. Multi-DOF entanglement that includes the OAM DOF has many superior properties; for example, it can increase the information carried by a single photon[25], further enhance the channel capacity and improve the efficiency of a network[22], and close the detection loophole in Bell experiments[26]. 2#3 hyperentanglement, consisting of two-dimensional (2D) entanglement between a collective atomic excited state ( called a spin wave) and photonic polarization as well as three-dimensional (3D) OAM entanglement between a spin wave and a single photon, is established between one atomic ensemble and a single photon through spontaneous Raman scattering (SRS) This entanglement is generated through an innovative method based on constructing a phase-insensitive interferometer, which allows the system to generate any of the four Bell states and operate for a long period of time without any locking technique. Our experimental results demonstrate the successful creation of memory-memory entanglement in multiple DOFs
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