Establishing and storing of deterministic quantum entanglement among three distant atomic ensembles

Abstract

It is crucial for the physical realization of quantum information networks to first establish entanglement among multiple space-separated quantum memories and then, at a user-controlled moment, to transfer the stored entanglement to quantum channels for distribution and conveyance of information. Here we present an experimental demonstration on generation, storage, and transfer of deterministic quantum entanglement among three spatially separated atomic ensembles. The off-line prepared multipartite entanglement of optical modes is mapped into three distant atomic ensembles to establish entanglement of atomic spin waves via electromagnetically induced transparency light–matter interaction. Then the stored atomic entanglement is transferred into a tripartite quadrature entangled state of light, which is space-separated and can be dynamically allocated to three quantum channels for conveying quantum information. The existence of entanglement among three released optical modes verifies that the system has the capacity to preserve multipartite entanglement. The presented protocol can be directly extended to larger quantum networks with more nodes.

Deterministically entangling multiple remote quantum memories inside an optical cavity

“…The time scale of adiabatically switching on and off is about 40 ns. The user-controlled time in our system is taken as 1 μs and the storage lifetime in the hot atomic ensemble is about 10 μs [37], which can be extended to the time scale of milliseconds with a paraffin-coated cell [30]. If a cold atomic ensemble is confined in an optical lattice, the storage lifetime can reach a time scale of seconds [39].…”

“…The quantum memory process is usually considered as a beam-splitter interaction and the vacuum noise is added to the input state as a result of limited memory efficiency [37,50,51]. Due to the imperfect experiment, the intracavity loss is also considered in our theory.…”

“…Quantum state mapping is one of the effective approaches to establish macroscopic object entanglement and the mapping efficiency is important for the entanglement quality [19,27,37]. In our proposal, the unconditional GHZ-like entangled state among multiple distant atomic ensembles is generated by mapping the multipartite entangled state from optical modes to atomic ensembles via CV cavity-enhanced quantum memory.…”

“…In the continuous-variable (CV) regime, which offers another path towards the realization of quantum information, unconditional entanglement among three atomic ensembles has been demonstrated by mapping a quantum state from three entangled optical modes to atomic ensembles. The improvement of the degree of atom entanglement is crucial for further application in quantum information [37]. * zhyan@sxu.edu.cn High-efficiency storage and release of the quantum state of optical modes in quantum nodes, as well as the establishment of high-quality entanglement among multiple remote quantum nodes, are required in high-fidelity quantum communication [33,34] and quantum computation [35].…”

“…* zhyan@sxu.edu.cn High-efficiency storage and release of the quantum state of optical modes in quantum nodes, as well as the establishment of high-quality entanglement among multiple remote quantum nodes, are required in high-fidelity quantum communication [33,34] and quantum computation [35]. In particular, in the quantum state mapping approach to the construction of quantum-node entanglement, the entanglement is sensitive to the squeezing of input optical modes and the memory efficiency of quantum nodes [19,27,37]. Therefore, it is essential to explore high-efficiency quantum memory.…”