Quantum controlled-phase-flip (CPF) gate between a flying photon qubit and a stationary atomic qubit could allow the linking of distant computational nodes in a quantum network. Here we present a scheme to realize quantum CPF gate between a flying optical photon and an atomic ensemble based on cavity input-output process and Rydberg blockade. When a flying single-photon pulse is reflected off the cavity containing a Rydberg atomic ensemble, the dark resonance and Rydberg blockade induce a conditional phase shift for the photon pulse, thus we can achieve the CPF gate between the photon and the atomic ensemble. Assisted by Rydberg blockade interaction, our scheme works in the N-atoms strong-coupling regime and significantly relaxes the requirement of strong coupling of single atom to photon in the optical cavity.

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We investigate the entanglement dynamics of an entangled atom pair via Wootters' concurrence. Only one atom of the pair interacts with a two-mode cavity field via a Raman interaction. The number simulation shows that the entanglement of the atom pair will display sudden death and revival phenomena when the cavity photon numbers and the two-mode atom–cavity coupling strengths are changed. Due to the two-mode field effect, the entanglement sudden death phenomenon will disappear more easily by enlarging the different cavity mode–atom coupling ratio. The oscillation rate of the concurrence is enlarged by increasing the mean photon number of the cavity field.

An electrochemical palladium/ferric oxide (Pd/Fe2O3) nanocomposite modified glassy carbon electrode (GCE) was fabricated by hydrothermal method of Fe2O3 and electrochemical deposition of palladium nanoparticles, respectively. As-prepared Pd/Fe2O3 composite modified electrode exhibits enhanced electrocatalytic activity towards the catalytic oxidation of nitrite compared to Fe2O3, PdNPs modified electrodes and bare electrode. The parameters such as the influence of amount of Pd nanoparticles deposition onto the Pd/Fe2O3 modified electrode (ME) and effect of solution pH were investigated and discussed in detail. Under the optimal conditions, the Pd/Fe2O3 modified GCE can be used to detect nitrite concentration in a wide linear range of 10 and 1000 μM with the detection limit of 0.1 μM. The presence of Cu2+, Na+, Cl-, PO3-4 SO2-4, Mg2+ K+, NO-3, and NH+4 showed a trivial effect on the response of nitrite determination, revealing that developed modified electrode has an excellent anti-interference ability to common ions. It also shows good stability and reproducibility.

A proposal for the generation of singlet states of three Λ-type Rydberg atoms is presented. The singlet state is prepared through the combination of a Rydberg state and an EPR pair, and the scheme relies on the Rydberg blockade effect which prevents the simultaneous excitation of the two atoms to a Rydberg state. In addition, some frequency detuning between lasers and atomic transitions is set to eliminate the degenerate of the two ground states. And finally, a series of numerical simulations are made to show the feasibility of the scheme.