Real-time quantum error correction beyond break-even.

The ambition of harnessing the quantum for computation is at odds with the fundamental phenomenon of decoherence. The purpose of quantum error correction (QEC) is to counteract the natural tendency of a complex system to decohere. This cooperative process, which requires participation of multiple quantum and classical components, creates a special type of dissipation that removes the entropy caused by the errors faster than the rate at which these errors corrupt the stored quantum information. Previous experimental attempts to engineer such a process1-7 faced the generation of an excessive number of errors that overwhelmed the error-correcting capability of the process itself. Whether it is practically possible to utilize QEC for extending quantum coherence thus remains an open question. Here we answer it by demonstrating a fully stabilized and error-corrected logical qubit whose quantum coherence is substantially longer than that of all the imperfect quantum components involved in the QEC process, beating the best of them with a coherence gain of G = 2.27 ± 0.07. We achieve this performance by combining innovations in several domains including the fabrication of superconducting quantum circuits and model-free reinforcement learning.

Electrocatalytic degradation kinetic of 4-chlorophenol by the Pd/C gas-diffusion electrode system.

A Pd/C gas-diffusion cathode which generated H2O2 through a two-electron reduction process of fed oxygen molecule was used to degrade 4-chlorophenol in an undivided electrolysis device. The kinetics of 4-chlorophenol degradation has been investigated by the electrochemical oxidation processes. By inspecting the relationship between the rate constants (k) and influencing factors, using first-order kinetics to describe the electrochemical oxidation process of 4-chlorophenol, a kinetic model of 4-chlorophenol degradation process was proposed to calculate the 4-chlorophenol effluent concentration: C = C0 exp( -3:76 × 10(-6) C(-0.5)0 J(2) M(-0.7) Q(0.17) Dt). It was found that the electrocatalytic degradation rate of 4-chlorophenol was affected by current density, electrode distance, air-feeding rate, electrolyte concentration and initial 4-chlorophenol concentration. The kinetics obtained from the experiments under corresponding electrochemical conditions could provide an accurate estimation of 4-chlorophenol effluent concentration and lead to better design of the electrochemical reactor.

[Determination of ofloxacin in human plasma and studies of its pharmacokinetics using HPLC method].

Ofloxacin is a new broad-spectrum oral bactericidal antimicrobial agent. Its primary effect is the inhibition of bacterial DNA gyrase. This paper describes the development of a simple method for its determination using HPLC with UV detection. We used a Waters liquid chromatograph equipped with a Model 490 E multi-wavelength detector, a Model 510 pump and a U6K injector. The separation was performed on a Spherisorb C18 column (200 mm x 4.6 mm ID, 5 microns) with a mobile phase of methanol-0.01 mol/L phosphate buffer-0.5 mol/L tetrabutylammonium bromide (35:65:4, pH 2.50). The flow-rate was 1.0 ml/min and detection was at 294 nm. A specimen (0.2 ml) was spiked with the internal standard (norfloxacin) and deproteinized by adding 1.0 ml methanol. The precipitated mixture was shaken and then centrifuged at 3000 x g for 10 min, the supernatant was evaporated at 75 degrees C under a nitrogen stream. The residue was taken up with 0.4 ml of the mobile phase and 50 microliters aliquots were injected into the system. The minimal detectable concentration in plasma is 20 ng/ml. There is a linear relationship between the peak area ratio over the range of 0.5-4.0 micrograms/ml with r = 0.9999. The method has been applied to assay ofloxacin concentration in human plasma. The pharmacokinetic characteristics were studied.