Pre-and post-selected measurements with coupling-strength-dependent modulation

Pre-and post-selected(PPS) measurement, especially the weak PPS measurement, has been proved to be a useful tool for measuring extremely tiny physical parameters. However, it is difficult to retain both the attainable highest measurement sensitivity and precision with the increase of the parameter to be measured. Here, a modulated PPS measurement scheme based on coupling-strength-dependent modulation is presented with the highest sensitivity and precision retained for an arbitrary coupling strength. This idea is demonstrated by comparing the modulated PPS measurement scheme with the standard PPS measurement scheme in the case of unbalanced input meter. By using the Fisher information metric, we derive the optimal pre-and post-selected states, as well as the optimal coupling-strength-dependent modulation without any restriction on the coupling strength. We also give the specific strategy of performing the modulated PPS measurement scheme, which may promote practical application of this scheme in precision metrology.

Extended validity of weak measurement

We introduce a modified weak value that is related to the mean value of input meter variable.With the help of the modified weak value,the validity conditions for various modified versions of weak value formalism are investigated,in terms of the dependence of the pointer shift on the mean value of the input meter.The weak value formalism,often used to represent the pointer shift,with the modified weak value is of great use in simplifying calculations and giving guidance of practical experiments whenever the mean value of the input meter variable is nonzero.The simulation in a qubit system is presented and coincident well with our theoretical result.

Parameter accuracy analysis of weak-value amplification process in the presence of noise

We theoretically introduce the statistical uncertainty of photon number and phase error to discuss the precision of parameters to be measured based on weak measurements. When the photon counting scheme is used, we discuss the relative accuracy of the system in the presence of phase error by using the orthogonal and nonorthogonal pre-and postselected states, respectively. When using the measurement scheme of pointer shift, we discuss the measurement accuracy in the presence of phase error, pointer resolution, and statistical uncertainty. These results give a guide way to get the smallest relative precision and deepen our understanding about weak measurement.

Highly active artificial potassium channels having record-high K^(+)/Na^(+) selectivity of 20.1

Replicating extraordinarily high membrane transport selectivity of protein channels in artificial channel is a challenging task.In this work,we demonstrate that a strategic application of steric code-based social self-sorting offers a novel means to enhance ion transport selectivities of artificial ion channels,alongside with boosted ion transport activities.More specifically,two types of mutually compatible sterically bulky groups(benzo-crown ether and tert-butyl group)were appended onto a monopeptide-based scaffold,which can order the bulky groups onto the same side of a one-dimensionally aligned H-bonded structure.Strong steric repulsions among the same type of bulky groups(either benzo-crown ethers or tert-butyl groups),which are forced into proximity by H-bonds,favor the formation of hetero-oligomeric ensem-bles that carry an alternative arrangement of sterically compatible benzo-crown ethers and tert-butyl groups,rather than homo-oligomeric ensembles containing a single type of either benzo-crown ethers or tert-butyl groups.Coupled with side chain tuning,this social self-sorting strategy delivers highly ac-tive hetero-oligomeric K+-selective ion channel(5F12-BF12)_(n),displaying the highest K+/Na+selectivity of 20.1 among artificial potassium channels and an excellent ECso value of 0.50μmol/L(0.62 mo1%relative to lipids)in terms of single channel concentration.

Steering paradox for Einstein–Podolsky–Rosen argument and its extended inequality

The Einstein–Podolsky–Rosen(EPR)paradox is one of the milestones in quantum foundations,arising from the lack of a local realistic description of quantum mechanics.The EPR paradox has stimulated an important concept of“quantum nonlocality,”which manifests itself in three types:quantum entanglement,quantum steering,and Bell’s nonlocality.Although Bell’s nonlocality is more often used to show“quantum nonlocality,”the original EPR paradox is essentially a steering paradox.In this work,we formulate the original EPR steering paradox into a contradiction equality,thus making it amenable to experimental verification.We perform an experimental test of the steering paradox in a two-qubit scenario.Furthermore,by starting from the steering paradox,we generate a generalized linear steering inequality and transform this inequality into a mathematically equivalent form,which is friendlier for experimental implementation,i.e.,one may measure the observables only in the x,y,or z axis of the Bloch sphere,rather than other arbitrary directions.We also perform experiments to demonstrate this scheme.Within the experimental errors,the experimental results coincide with theoretical predictions.Our results deepen the understanding of quantum foundations and provide an efficient way to detect the steerability of quantum states.