We propose a scheme to directly measure the exact value of geometric quantum discord of an arbitrary two-qubit state. We only need to perform the projective measurement in the all anti-symmetric subspace and our scheme is parametrically efficient in contrast to the widely adopted quantum state tomography scheme in the sense of less parameter estimations and projectors. Moreover, the present scheme can be easily realized with the current experimental techniques.

Cu is a unique catalyst for CO electroreduction, since it can catalyze CO reduction to a series of hydrocarbons, alcohols, and carboxylic acids. Nevertheless, such Cu catalysts suffer from poor selectivity. High pressure of CO is considered to facilitate the activity and selectivity of CO reduction. Herein, a new strategy is presented for CO reduction with improved C H selectivity on a Cu catalyst by using CO capture materials as the support at ambient pressure. N-doped carbon (N C) was synthesized through high-temperature carbonization of melamine and l-lysine. We observed that the CO uptake capacity of N C depends on both the microporous area and the content of pyridinic N species, which can be controlled by the carbonization temperature (600-800 °C). The as-prepared CuO/N C catalysts exhibit a considerably higher C H faradaic efficiency (36 %) than CuO supported on XC-72 carbon black (19 %), or unsupported CuO (20 %). Moreover, there is a good linear relationship between the C H faradaic efficiency and CO uptake capacity of the supports for CuO. The local high CO concentration near Cu catalysts, created by CO capture materials, was proposed to increase the coverage of CO intermediate, which is favorable for the coupling of two CO units in the formation of C H . This study demonstrates that pairing Cu catalysts with CO capture supports is a promising approach for designing highly effective CO reduction electrocatalysts.

We propose a simple method for achieving a multiqubit phase gate of one qubit simultaneously controlling n target qubits, by using three-level quantum systems (i.e., qutrits) coupled to a cavity or resonator. The gate can be realized via one operational step, without need of classical pulses, and by a virtual photon process. Thus, the gate operation is greatly simplified and decoherence from the cavity decay is much reduced, when compared with previous proposals. In addition, the operation time is independent of the number of qubits and no adjustment of the qutrit level spacings or the cavity frequency is needed during the operation.

We investigated CO electroreduction on Cu overlayers on tetrahexahedral Pd nanocrystals with {310} high-index facets, which exhibited a high Faradaic efficiency towards alcohols. The selectivity to ethanol or methanol can be readily tuned by changing the Cu coverage.

We investigate the single photon scattering by an emitter chirally coupled to a one-dimensional waveguide. The single-photon transport property is essentially different from the symmetrical coupling case. The single photons propagating towards the emitter in opposite directions show different transmission behaviors, which is a manifestation of the single-photon diode. In the ideal chiral coupling case, the transmission probability of the single photon transport in one direction is zero by critical coupling, while in the opposite direction it is unity. The diode works well only when the single-photon frequency meets certain conditions. For a two-level emitter, the diode works well when the single photon is nearly resonant to the emitter. For a Λ-type three-level emitter, when the single-photon frequency is greatly altered, we can adjust the parameters of the external laser to ensure the diode works well. The latter provides a manner to realize a single-photon switch, in which the single-photon transmission probability can reach zero or unity although the emitter's decay is considered.

Nowadays, quantum router is playing a key role in quantum communication and quantum networks. Here we propose a tunable single-photon routing scheme, based on quantum interference, which uses two distant artificial atoms coupling to two transmission lines. Depending on the distance between the two atoms, the collective effect will lead to destructive or constructive interference between the scattered photons. Under standing wave condition, single photon from the incident channel can be perfectly transmitted or redirected into another channel by asymmetric or symmetric reflected phase shift of atoms, respectively. Therefore, we show that our router can be controlled by adjusting the detuning of the atoms and interatomic distance, without any classical field.

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Schrödinger’s cat paradox has revealed the entanglement between microscopic and macroscopic objects. Recently, several approaches have been proposed to generate such hybrid entangled state. In this paper, we demonstrate the generation of generalized hybrid entangled state in a cavity electro–optic system. The hybrid entangled state between the optical cavity and the microwave field is generated by a one-step evolution. Numerical simulations show that the high-fidelity entangled state is obtained even if the decay of the system is considered. Also, this proposal can be applied to generate macroscopic quantum superposition states of the microwave field.