Experimental realization of entanglement in multiple degrees of freedom between two quantum memories

Ding, Dong-Sheng; Dong, Ming‐Xin; Shi, Shuai; Wang, Kai; Liu, Shi-Long; Li, Yan; Zhou, Zhi-Yuan; Shi, Bao‐Sen; Guo, Guang‐Can

doi:10.1038/ncomms13514

Cited by 77 publications

(37 citation statements)

References 40 publications

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“…Note that previous demonstrations of HD entanglement heavily relied on subtraction of accidental background [27,32,33] and in consequence only estimated the number K of Schmidt modes potentially available while not confirming the presence of certified entanglement or EPR-steering. Other experiments utilize various types of spatial modes but allowed measurement of only a single mode-pair at-a-time [31,[46][47][48][49][50]. For certification of EPR-steering we use a coarse-grained analogue of the entropic witness [26,47]:…”

Section: Methodsmentioning

confidence: 99%

Certification of high-dimensional entanglement and Einstein-Podolsky-Rosen steering with cold atomic quantum memory

et al. 2018

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The advent of complex, structured and high-dimensional entangled statesbring both new possibilities for experimental and theoretical scenarios as well as new challenges for generation and characterization of such states. In particular, spatially-structured photonic states offer applications in quantum imaging, information processing, and quantum key distribution. Here we experimentally generate a spatially entangled high-dimensional state composed of at least 10 Schmidt modes in a quantum memory setup and perform characterization using the entropic EPR-steering inequality, yielding genuine violation of 1.06 ± 0.15 bits. The entanglement of formation of at least 0.70 ± 0.15 ebits for the measured noisy state is certified using the entropic witness method. We point out and solve the difficulties in estimating the entropy, achieving characterization of the high-dimensional entangled state with highly undersampled data. Finally, the practical supremacy of the entropic EPR-steering witness over a variance-based witness is demonstrated for a wide class of states typical in an experimental scenario, giving prospects for EPR-steering demonstrations and applications in noisy systems or with lossy quantum channels.

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Section: Methodsmentioning

confidence: 99%

Certification of high-dimensional entanglement and Einstein-Podolsky-Rosen steering with cold atomic quantum memory

et al. 2018

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“…Single atoms [3,4], atomic ensembles[5-10], trapped ions [11][12][13], optomechanics[14-17], superconductors[18], solid-state systems [19][20][21][22] and so on have been applied as quantum nodes. Especially, atomic ensembles are among the best candidates for quantum nodes to store and process quantum information due to the advantage of the collective enhancement of light-atom interaction [5][6][7][8][9][10].The entanglement of discrete quantum variables between two atomic ensembles has been experimentally achieved by means of Raman scattering approach [23,24] or transferring quantum states of entangled photons into two atomic systems [25][26][27]. In 2010, Kimble's group demonstrated measurement-induced entanglement stored in four atomic memories and coherent transfer of the atomic entanglement to four photonic channels [28].…”

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confidence: 99%

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

Yan

Jia

et al. 2017

Nat Commun

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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.

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“…Our experiment is an important step toward quantum repeaters and quantum networks using multiplexed quantum memories and high-dimensional entanglement. If each memory cell can store a photon carrying other degrees of freedom [37], we can combine the advantages of high dimensional entangled state and multiplexed quantum memory together and expect further improvement in the performance. array with the highest and nearly uniform retrieval efficiency and optical depth for each memory cell.…”

Section: Discussionmentioning

confidence: 99%

High-dimensional entanglement between a photon and a multiplexed atomic quantum memory

Chang

et al. 2020

Phys. Rev. A

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Multiplexed quantum memories and high-dimensional entanglement can improve the performance of quantum repeaters by promoting the entanglement generation rate and the quantum communication channel capacity. Here, we experimentally generate a high-dimensional entangled state between a photon and a collective spin wave excitation stored in the multiplexed atomic quantum memory. We verify the entanglement dimension by the quantum witness and the entanglement of formation. Then we use the high-dimensional entangled state to test the violation of the Bell-type inequality. Our work provides an effective method to generate multidimensional entanglement between the flying photonic pulses and the atomic quantum interface. I. INTRODUCTIONLong distance quantum communication requires quantum entanglement distributed over two end nodes of a quantum communication channel [1][2][3]. Due to the optical absorption and other noise in the channel, the error of direct communication increases exponentially with the distance, thus reduces the key rates in quantum key distribution. To overcome this problem, the quantum repeater protocol has been proposed, where a series of entanglement generation and swapping operations are performed to extend the entanglement to farther and farther nodes with only polynomial cost [4]. The practical utilization of a quantum repeater requires quantum memories [5,6]. Pioneering works have been demonstrated toward the implementation of a quantum repeater with atomic quantum memory. For example, photonic qubits have been stored as collective spin wave excitations in the atomic ensemble [7][8][9]; entanglement between the memory and transmitting photons has also been realized [10][11][12].Several methods have been proposed to further improve the quantum repeater protocol. One is to use multiplexed quantum memories, which significantly reduce the required time to establish entanglement in the quantum communication channel [13][14][15]. Another possibility is to explore high-dimensional entanglement in the quantum network [16,17], which increases the capacity of the communication channel and thus enhances the quantum communication efficiency [18]. High-dimensional entanglement also has plenty of applications beyond quantum communication, such as quantum teleportation with high capacity [19][20][21], quantum distillation [22,23] and robust Bell tests [24,25]. Recently, many efforts have been devoted to creating high-dimensional entanglement sources in different systems, like rare-earth-doped crystals [26- * Present address: 32], integrated devices [25,32] and atomic systems [33][34][35]. Moreover, the photonic qudits possessing the highdimensional entanglement have been stored in quantum memory elements, based on atomic ensembles [36,37] or rare-earth-doped crystals [9,26,38].

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Experimental realization of entanglement in multiple degrees of freedom between two quantum memories

Cited by 77 publications

References 40 publications

Certification of high-dimensional entanglement and Einstein-Podolsky-Rosen steering with cold atomic quantum memory

Certification of high-dimensional entanglement and Einstein-Podolsky-Rosen steering with cold atomic quantum memory

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

High-dimensional entanglement between a photon and a multiplexed atomic quantum memory

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