Wave Function Engineering for Spectrally-Uncorrelated Biphotons in the Telecommunication Band based on a Machine-Learning Framework

Indistinguishable single photons are key ingredient for a plethora of quantum information processing applications ranging from quantum communications to photonic quantum computing. A mainstream platform to produce indistinguishable single photons over a wide spectral range is based on biphoton generation through spontaneous parametric down-conversion (SPDC) in nonlinear crystals. The purity of the SPDC biphotons, however, is limited by their spectral correlations. Here, we present a design recipe, based on a machine-learning framework, for the engineering of biphoton joint spectrum amplitudes over a wide spectral range. By customizing the poling profile of the KTiOPO$_4$ (KTP) crystal, we show, numerically, that spectral purities of 99.22%, 99.99%, and 99.82% can be achieved, respectively, in the 1310-nm, 1550-nm, and 1600-nm bands after applying a moderate 8-nm filter. The machine-learning framework thus enables the generation of near-indistinguishable single photons over the entire telecommunication band without resorting to KTP crystal's group-velocity-matching wavelength window near 1582 nm

Jacobson’s lemma for the generalized Drazin inverse

Abstract0truemm0truemm We study properties of elements in a ring which admit the generalized Drazin inverse. It is shown that the element 1-ab is generalized Drazin invertible if and only if so is 1-ba and a formula for the generalized Drazin inverse of 1-ba in terms of the generalized Drazin inverse and the spectral idempotent of 1-ab is provided. Further, recent results relating to the Drazin index can be recovered from our theorems

Why torus-unstable solar filaments experience failed eruption?

To investigate the factors that control the success and/or failure of solar eruptions, we study the magnetic field and 3-Dimensional (3D) configuration of 16 filament eruptions during 2010 July - 2013 February. All these events, i.e., erupted but failed to be ejected to become a coronal mass ejection (CME), are failed eruptions with the filament maximum height exceeding $100 Mm$. The magnetic field of filament source regions is approximated by a potential field extrapolation method. The filament 3D configuration is reconstructed from three vantage points by the observations of STEREO Ahead/Behind and SDO spacecraft. We calculate the decay index at the apex of these failed filaments and find that in 7 cases, their apex decay indexes exceed the theoretical threshold ($n_{crit} = 1.5$) of the torus instability. We further determine the orientation change or rotation angle of each filament top during the eruption. Finally, the distribution of these events in the parameter space of rotation angle versus decay index is established. Four distinct regimes in the parameter space are empirically identified. We find that, all the torus-unstable cases (decay index $n > 1.5$), have a large rotation angles ranging from $50^\circ - 130^\circ$. The possible mechanisms leading to the rotation and failed eruption are discussed. These results imply that, besides the torus instability, the rotation motion during the eruption may also play a significant role in solar eruptions

What do seller manipulations of online product reviews mean to consumers?

There is growing evidence that consumers are influenced by online product reviews when making a variety of purchase decisions. Firms are therefore tempted to monitor and manipulate online product reviews on the company\u27s website or forum to influence consumer perceptions by anonymously posting positive reviews, hiding or deleting unfavorable reviews, or offering rewards to consumers who post favorable reviews. Our review of the literature has revealed a surprising shortage of work directed at the development of an integrative theoretical framework or rigorous empirical studies on the effectiveness and the exact impact of such activities on the payoffs to various parties. This study fills a void in the online marketing and information manipulation literature by studying consumers\u27 suspicion, awareness and evaluation of specific manipulation tactics through in-depth interviews with 16 experienced online shoppers in China. We adopt a grounded theory approach to analyze the qualitative data and end up with a series of research propositions (research framework) for further testing and verification. The findings about consumers\u27 views of online manipulations would provide valuable insights to industry associations and policy makers on whether and how to regulate online manipulation activities to ensure the healthy development of the e-commerce

Deterministic microwave-optical transduction based on quantum teleportation

The coherent transduction between microwave and optical frequencies is critical to interconnect superconducting quantum processors over long distances. However, it is challenging to establish such a quantum interface with high efficiency and small added noise based on the standard direct conversion scheme. Here, we propose a transduction scheme based on continuous-variable quantum teleportation. Reliable quantum information transmission can be realized with an arbitrarily small cooperativity, in contrast to the direct conversion scheme which requires a large minimum cooperativity. We show that the teleportation-based scheme maintains a significant rate advantage robustly for all values of cooperativity. We further investigate the performance in the transduction of complex quantum states such as cat states and Gottesman-Kitaev-Preskill(GKP) states and show that a higher fidelity or success probability can be achieved with the teleportation-based scheme. Our scheme significantly reduces the device requirement, and makes quantum transduction between microwave and optical frequencies feasible in the near future.Comment: 5+9 pages, 9 figure