Abstract Atomic ensembles are important quantum resources for the generation, manipulation, and quantum memory of entangled photons. In photonic quantum information based on atom–photon interactions, high‐quality entangled‐photon‐pair sources are essential for realizing quantum information networks consisting of channels to connect the nodes through atomic ensembles. Here, a proof‐of‐concept for controlling polarization‐entangled photon‐pair sources from atomic ensembles by an external magnetic field under a magnetic noise environment is demonstrated. In the unshielded magnetic field, the polarization entangled state of the photon pair could be optimized to the target state by adjusting the magnetic field in an atomic vapor cell. The polarization‐interference fringe, Bell's inequality value, quantum state tomography, and Hong–Ou–Mandel interference of the polarization entangled photon pairs from the cascade‐type 5S 1/2 –5P 3/2 –5D 5/2 transition of 87 Rb according to the direction of the external magnetic field. Accordingly, a magnetic field is found to be a promising means for controlling entangled two‐qubit states based on atom–photon.Abstract Atomic ensembles are important quantum resources for the generation, manipulation, and quantum memory of entangled photons. In photonic quantum information based on atom–photon interactions, high‐quality entangled‐photon‐pair sources are essential for realizing quantum information networks consisting of channels to connect the nodes through atomic ensembles. Here, a proof‐of‐concept for controlling polarization‐entangled photon‐pair sources from atomic ensembles by an external magnetic field under a magnetic noise environment is demonstrated. In the unshielded magnetic field, the polarization entangled state of the photon pair could be optimized to the target state by adjusting the magnetic field in an atomic vapor cell. The polarization‐interference fringe, Bell's inequality value, quantum state tomography, and Hong–Ou–Mandel interference of the polarization entangled photon pairs from the cascade‐type 5S 1/2 –5P 3/2 –5D 5/2 transition of 87 Rb according to the direction of the external magnetic field. Accordingly, a magnetic field is found to be a promising means for controlling entangled two‐qubit states based on atom–photon.

Advanced Quantum TechnologiesJan 29, 20233 citations

Experimental Atom-Photon Entanglement:

Markus Weber, Juergen Volz, Wenjamin Rosenfeld +4 more

Bulletin of the American Physical SocietyMay 18, 20060 citations

Noise suppression in a temporal-multimode quantum memory entangled with a photon via an asymmetrical photon-collection channel

Ya Li, Yafei Wen, Minjie Wang +5 more

Quantum interfaces (QIs) that generate entanglement between a multimode atomic memory and a photon form a multiplexed repeater node and could greatly improve quantum repeater rates. Recently, a temporal multimode spin-wave memory entangled with a photon was demonstrated with cold atoms [Wen et al., Phys. Rev. A 100, 012342 (2019)]. However, due to the additional noise generated in a multimode operation, the fidelity of the spin-wave--photon entanglement significantly decreases with the mode number. So far, improvements in the temporal-multimode entanglement fidelity associated with suppressing the additional noise have not been explored. In this work, we propose and experimentally demonstrate a scheme that can suppress the additional noise of a temporally multiplexed QI. The scheme uses an asymmetric channel to retrieve the photons coming from the temporally multiplexed QI. For comparison purposes, we also set up a QI that uses a symmetric channel for photon collection. When the QIs store 14 modes, the measured Bell parameters $S$ for the QIs using the asymmetric and the symmetric photon-collection channels are 2.36 \ifmmode\pm\else\textpm\fi{} 0.03 and 2.24 \ifmmode\pm\else\textpm\fi{} 0.04, respectively, which means that a QI using an asymmetric channel provides a 3% increase in the entanglement fidelity, i.e., a 1.7-fold decrease in the additional noise, compared with a QI using a symmetric channel. In addition, the 14-mode entanglement QIs that use the asymmetric and symmetric collections preserve the violation of a Bell inequality for storage times of up to \ensuremath{\sim}25 and \ensuremath{\sim}20 \ensuremath{\mu}s, respectively, showing that the asymmetric QI has better entanglement storage performance.Quantum interfaces (QIs) that generate entanglement between a multimode atomic memory and a photon form a multiplexed repeater node and could greatly improve quantum repeater rates. Recently, a temporal multimode spin-wave memory entangled with a photon was demonstrated with cold atoms [Wen et al., Phys. Rev. A 100, 012342 (2019)]. However, due to the additional noise generated in a multimode operation, the fidelity of the spin-wave--photon entanglement significantly decreases with the mode number. So far, improvements in the temporal-multimode entanglement fidelity associated with suppressing the additional noise have not been explored. In this work, we propose and experimentally demonstrate a scheme that can suppress the additional noise of a temporally multiplexed QI. The scheme uses an asymmetric channel to retrieve the photons coming from the temporally multiplexed QI. For comparison purposes, we also set up a QI that uses a symmetric channel for photon collection. When the QIs store 14 modes, the measured Bell parameters $S$ for the QIs using the asymmetric and the symmetric photon-collection channels are 2.36 \ifmmode\pm\else\textpm\fi{} 0.03 and 2.24 \ifmmode\pm\else\textpm\fi{} 0.04, respectively, which means that a QI using an asymmetric channel provides a 3% increase in the entanglement fidelity, i.e., a 1.7-fold decrease in the additional noise, compared with a QI using a symmetric channel. In addition, the 14-mode entanglement QIs that use the asymmetric and symmetric collections preserve the violation of a Bell inequality for storage times of up to \ensuremath{\sim}25 and \ensuremath{\sim}20 \ensuremath{\mu}s, respectively, showing that the asymmetric QI has better entanglement storage performance.

arXiv:2111.00381Physical Review AAug 15, 20228 citations

Effect of biased noise fluctuations on entanglement and statistical properties in a two-photon phase-sensitive laser

Sintayehu Tesfa

Analysis of the effects of the biased noise fluctuations on the quantum features and statistical properties of the cavity radiation of the two-photon phase-sensitive laser is presented. It turns out that the biased noise fluctuations that enter the cavity via the vibrations of the wall enhance the atomic coherence responsible for the entanglement of the cavity radiation due to the phase sensitivity of the involved cascade transitions. The two-mode squeezing of the superimposed radiation, entanglement of the cavity radiation, and mean number of the photon pairs are found to increase with the rate at which the atoms are injected into the cavity. The two-mode squeezing increases with the intensity of the biased noise fluctuations, but the mean number of the photon pairs decreases. Even then, it is possible to produce quite intense robust continuous variable entanglement in this scheme which is believed to be a motivation for further practical scrutiny. Moreover, the superimposed radiation exhibits super-Poissonian photon statistics with no finite joint probability for getting more photons in mode $b$ than mode $a$ .Analysis of the effects of the biased noise fluctuations on the quantum features and statistical properties of the cavity radiation of the two-photon phase-sensitive laser is presented. It turns out that the biased noise fluctuations that enter the cavity via the vibrations of the wall enhance the atomic coherence responsible for the entanglement of the cavity radiation due to the phase sensitivity of the involved cascade transitions. The two-mode squeezing of the superimposed radiation, entanglement of the cavity radiation, and mean number of the photon pairs are found to increase with the rate at which the atoms are injected into the cavity. The two-mode squeezing increases with the intensity of the biased noise fluctuations, but the mean number of the photon pairs decreases. Even then, it is possible to produce quite intense robust continuous variable entanglement in this scheme which is believed to be a motivation for further practical scrutiny. Moreover, the superimposed radiation exhibits super-Poissonian photon statistics with no finite joint probability for getting more photons in mode $b$ than mode $a$.

Physical Review AJan 17, 200831 citations

Influence of atom-photon correlations on atom-atom entanglement

F. Lastra, Sascha Wallentowitz

Nov 18, 20090 citations

S

for the QIs using the asymmetric and the symmetric photon-collection channels are 2.36 \ifmmode\pm\else\textpm\fi{} 0.03 and 2.24 \ifmmode\pm\else\textpm\fi{} 0.04, respectively, which means that a QI using an asymmetric channel provides a 3% increase in the entanglement fidelity, i.e., a 1.7-fold decrease in the additional noise, compared with a QI using a symmetric channel. In addition, the 14-mode entanglement QIs that use the asymmetric and symmetric collections preserve the violation of a Bell inequality for storage times of up to \ensuremath{\sim}25 and \ensuremath{\sim}20 \ensuremath{\mu}s, respectively, showing that the asymmetric QI has better entanglement storage performance.

b

than mode

a