We demonstrate the collapse and revival features of the entanglement dynamics of different polarization-entangled photon states in a non-Markovian environment. Using an all-optical experimental setup, we show that entanglement can be revived even after it suffers from sudden death. A maximally revived state is shown to violate a Bell's inequality with 4.1 standard deviations which verifies its quantum nature. The revival phenomenon observed in this experiment provides an intriguing perspective on entanglement dynamics.PACS numbers: 03.67. Mn, 03.65.Ud, 03.65.Yz Quantum entanglement, which is a kind of counterintuitive nonlocal correlation, is fundamental in quantum physics both for its essential role in understanding the nonlocality of quantum mechanics [1,2] and its practical application in quantum information processing [3,4]. However, entanglement will become degraded due to the unavoidable interaction with the environment [5,6]. Recently, the dynamics of entanglement in different noise channels has attracted extensive interests [7][8][9][10][11][12][13][14][15][16][17][18]. Surprisingly, the evolution of entanglement may possess some distinct properties. It has been shown that entanglement between two particles evolved in independent reservoirs may disappear completely at a finite time in spite of the asymptotical coherence decay of single particle [7][8][9][10]. This phenomenon, termed as entanglement sudden death (ESD) [10], has been experimentally observed in Markovian environments [16,17] (for a review see [18] and references therein). Moreover, different from the irreversible disentanglement process in the Markovian environment, non-Markovian noise with memory effect may contribute to the revival of entanglement even after ESD occurs [7,[11][12][13][14]. Here, we experimentally investigate the collapse and revival of entanglement of two photons with one of them passing through a birefringent nonMarkovian environment, which is simulated by a special designed Fabry-Perot (FP) cavity followed by quartz plates. We observe the revival of entanglement after it suffers from sudden death. A maximally revived state is shown to violate a Bell's inequality with 4.1 standard deviations which disproves its local realistic description.Consider one of the maximally entangled polarization states |φ = 1/ √ 2(|HH a,b + |V V a,b ), where H and V represent the horizontal and vertical polarizations, respectively. The subscripts a and b denote the different paths of the photons. If the photon in mode b passes through birefringent crystals (quartz plates) with the optic axes set to be horizontal, the final polarization state of the two photons can be written as the following reduced * email: cfli@ustc.edu.cn † email: xbz@ustc.edu.cnwhere the decoherence parameterdenoting the amplitude corresponding to the frequency ω b of the photon in mode b and being normalized as f (ω b )dω b = 1. In our case, α = L∆n/c where L is the thickness of quartz plates and c represents the velocity of the photon in the vacuum. ∆n = n o − n e is...
Here we present the quantum storage of three-dimensional orbital-angular-momentum photonic entanglement in a rare-earth-ion-doped crystal. The properties of the entanglement and the storage process are confirmed by the violation of the Bell-type inequality generalized to three dimensions after storage (S=2.152±0.033). The fidelity of the memory process is 0.993±0.002, as determined through complete quantum process tomography in three dimensions. An assessment of the visibility of the stored weak coherent pulses in higher-dimensional spaces demonstrates that the memory is highly reliable for 51 spatial modes. These results pave the way towards the construction of high-dimensional and multiplexed quantum repeaters based on solid-state devices. The multimode capacity of rare-earth-based optical processors goes beyond the temporal and the spectral degree of freedom, which might provide a useful tool for photonic information processing.
Quantum repeaters are critical components for distributing entanglement over long distances in presence of unavoidable optical losses during transmission. Stimulated by the Duan–Lukin–Cirac–Zoller protocol, many improved quantum repeater protocols based on quantum memories have been proposed, which commonly focus on the entanglement-distribution rate. Among these protocols, the elimination of multiple photons (or multiple photon-pairs) and the use of multimode quantum memory are demonstrated to have the ability to greatly improve the entanglement-distribution rate. Here, we demonstrate the storage of deterministic single photons emitted from a quantum dot in a polarization-maintaining solid-state quantum memory; in addition, multi-temporal-mode memory with 1, 20 and 100 narrow single-photon pulses is also demonstrated. Multi-photons are eliminated, and only one photon at most is contained in each pulse. Moreover, the solid-state properties of both sub-systems make this configuration more stable and easier to be scalable. Our work will be helpful in the construction of efficient quantum repeaters based on all-solid-state devices.
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