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 i...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.展开更多
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...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.展开更多
Bell＇s theorem without inequalities is applied for some general Greenberger-Horn-Zeilinger （GHZ） states and W states and a wide range of such states can exhibit all-versus-nothing conflict between local realism and...Bell＇s theorem without inequalities is applied for some general Greenberger-Horn-Zeilinger （GHZ） states and W states and a wide range of such states can exhibit all-versus-nothing conflict between local realism and quantum theory. The case of standard GHZ state is contained in our proposal. For some generalized GHZ states more intensive violation on local realism is manifested.展开更多
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 dis...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.展开更多
基金National Key R&D Program of China(Grant No.2017YFA0305200)the National Natural Science Foundation of China(Grant Nos.11674234 and 11605205)+4 种基金the Natural Science Foundation of Chongqing,China(Grant Nos.cstc2015jcyjA00021 and cstc2018jcyjAX0656)Innovation Project of Sichuan University,China(Grant No.2018SCUH0021)the Youth Innovation Promotion Association,Chinese Academy of Sciences(Grant No.2015317)the Entrepreneurship and Innovation Support Program for Chongqing Overseas Returnees,China(Grant Nos.cx2017134 and cx2018040)the Fund of CAS Key Laboratory of Microscale Magnetic Resonance,and the Fund of CAS Key Laboratory of Quantum Information,China.
文摘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.
基金supported by the National Natural Science Foundation of China(Grant Nos.11674234 and 11605205)the Fundamental Research Funds for the Central Universities,China(Grant No.2012017yjsy143)+4 种基金the National Key Research and Development Program of China(Grant No.2017YFA0305200)the Youth Innovation Promotion Association of Chinese Academy of Sciences(CAS)(Grant No.2015317)the Natural Science Foundation of Chongqing,China(Grant Nos.cstc2015jcyjA00021 and cstc2018jcyjAX0656)the Entrepreneurship and Innovation Support Program for Chongqing Overseas Returnees,China(Grant No.cx017134)the Fund of CAS Key Laboratory of Microscale Magnetic Resonance,China,and the Fund of CAS Key Laboratory of Quantum Information,China
文摘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.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10375057 and 10425524, the National Basic Research Programme of China under Grant No 2001CB309300, the ASTAR （No 012-304-105）, Chinese Academy of Sciences. and the Marie Curie Action Programme of the European Union.
文摘Bell＇s theorem without inequalities is applied for some general Greenberger-Horn-Zeilinger （GHZ） states and W states and a wide range of such states can exhibit all-versus-nothing conflict between local realism and quantum theory. The case of standard GHZ state is contained in our proposal. For some generalized GHZ states more intensive violation on local realism is manifested.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0305200)the National Natural Science Foundation of China (Grant Nos. 11674234 and 11605205)+5 种基金the Natural Science Foundation of Chongqing (Grant Nos. cstc2015jcyjA00021 and cstc2018jcyjAX0656)the Innovation Project of Sichuan University (Grant No. 2018SCUH0021)the Youth Innovation Promotion Association Program of the Chinese Academy of Sciences (CAS)(Grant No. No. 2015317)the Entrepreneurship and Innovation Support Program for Chongqing Overseas Returnees (Grant Nos. cx2017134and cx2018040)the Fund of CAS Key Laboratory of Microscale Magnetic Resonancethe Fund of CAS Key Laboratory of Quantum Information。
文摘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.
