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Dive into the research topics where Shunlong Luo is active.

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Featured researches published by Shunlong Luo.


IEEE Transactions on Information Theory | 2004

On skew information

Shunlong Luo; Qiang Zhang

In this paper, we show that skew information introduced by Wigner and Yanase, which is a natural informational extension of variance for pure states, can be interpreted as a measure of quantum uncertainty. By virtue of skew information, we establish a new uncertainty relation in the spirit of Schrodinger, which incorporates both incompatibility (encoded in the commutator) and correlations (encoded in a new correlation measure related to skew information) between observables, and moreover is stronger than the conventional ones.


Proceedings of the American Mathematical Society | 2004

Wigner-Yanase skew information vs. quantum Fisher information

Shunlong Luo

Among concepts describing the information contents of quantum mechanical density operators, both the Wigner-Yanase skew information and the quantum Fisher information defined via symmetric logarithmic derivatives are natural generalizations of the classical Fisher information. We will establish a relationship between these two fundamental quantities and show that they are comparable.


Letters in Mathematical Physics | 2000

Quantum Fisher Information and Uncertainty Relations

Shunlong Luo

It is well known that the Cramér–Rao inequality places a lower bound for quantum Fisher information in terms of the variance of any quantum measurement. We establish an upper bound for quantum Fisher information of a parameterized family of density operators in terms of the variance of the generator. These two bounds together yield a generalization of the Heisenberg uncertainty relations from statistical estimation perspective.


Physical Review A | 2014

Quantum speedup in a memory environment

Zhen-Yu Xu; Shunlong Luo; W. L. Yang; Chen Liu; Shiqun Zhu

Memory (non-Markovian) effect is found to be able to accelerate quantum evolution [S. Deffner and E. Lutz, Phys. Rev. Lett. 111, 010402 (2013).]. In this work, for an atom in a structured reservoir, we show that the mechanism for the speedup is not only related to non-Markovianity but also to the population of excited states under a given driving time. In other words, it is the competition between non-Markovianity and population of excited states that ultimately determines the acceleration of quantum evolution in memory environments. A potential experimental realization for verifying the above phenomena is discussed by using a nitrogen-vacancy center embedded in a planar photonic crystal cavity under current technologies.


Journal of Physics A | 2002

Fisher information, kinetic energy and uncertainty relation inequalities

Shunlong Luo

By interpolating between Fisher information and mechanical kinetic energy, we introduce a general notion of kinetic energy with respect to a parameter of Schrodinger wavefunctions from a statistical inference perspective. Kinetic energy is the sum of Fisher information and an integral of a parametrized analogue of quantum mechanical current density related to phase. A family of integral inequalities concerning kinetic energy and moments are established, among which the Cramer–Rao inequality and the Weyl–Heisenberg inequality, are special cases. In particular, the integral inequalities involving the negative order moments are relevant to the study of electron systems. Moreover, by specifying the parameter to a scale, we obtain a family of inequalities of uncertainty relation type which incorporate the position and momentum observables symmetrically in a single quantity.


EPL | 2010

Global effects of quantum states induced by locally invariant measurements

Shunlong Luo; Shuangshuang Fu

In quantum mechanics, general measurements often cause disturbance which may be exploited to quantify entanglement, nonlocality or quantumness. Imagine a bipartite state ρab shared by two parties a and b, and a von Neumann measurement performed locally on party a which does not disturb the local state ρa:=tr b ρab, but nevertheless may disturb the global state ρab. This disturbance is an indication of some kind of correlations or global effect in ρab which cannot be accounted for locally. We propose to use the maximum disturbance on ρab caused by locally non-disturbing measurements as a figure of merit quantifying the global effect (nonlocality), and investigate its fundamental properties. For general two-qubit states and some higher-dimensional symmetric states, we present analytic formulas for their global effects.


IEEE Transactions on Information Theory | 2005

Correction to “On Skew Information”

Shunlong Luo; Qiang Zhang

In the above titled paper (ibid., vol. 50, no. 8, pp. 1778-1782, Aug 04), changes were made to Figure 2, Theorem 1.


International Journal of Theoretical Physics | 2002

Statistics of Local Value in Quantum Mechanics

Shunlong Luo

Given a quantum mechanical observable and a state, one can construct a classical observable, that is, a real function on the configuration space, such that it is the optimal estimate of the quantum observable, in the sense of minimum variance. This optimal estimate turns out to be the quantum mechanical local value, which arises from several contexts such as de Broglie–Bohms casual approach to quantum mechanics, instantaneous frequency in time–frequency analysis, Nelsons quantum fluctuations formalism, and phase-space approach to quantum mechanics. Accordingly, any observable can be decomposed into a local value part and a quantum fluctuation part, which are independent, both geometrically and statistically. Furthermore, the current density in quantum mechanics, the osmotic velocity in stochastic mechanics, and the Fisher information in classical statistical inference, arise naturally in connection with local value. In particular, Heisenberg uncertainty principle can be quantified more precisely by virtue of local value.


Physical Review A | 2010

Decomposition of bipartite states with applications to quantum no-broadcasting theorems

Shunlong Luo; Wei Sun

Correlations in bipartite quantum states are fundamental objects in quantum information theory. A canonical framework for studying correlations is the entangled versus separable dichotomy in which the decompositions of separable states as convex combinations of product states play an instrumental role. In this paper, motivated by both the representation of separable states and quantum no-broadcasting considerations, we establish a constructive decomposition representation for any bipartite state. As applications, we prove the conjectures proposed by Luo [Lett. Math. Phys. 92, 143 (2010)] concerning no-unilocal broadcasting for quantum correlations and further provide a unified picture for the celebrated quantum no-broadcasting theorem for noncommuting states by Barnum et al. [Phys. Rev. Lett. 76, 2818 (1996)], and the elegant no-local-broadcasting theorem for quantum correlations by Piani et al. [Phys. Rev. Lett. 100, 090502 (2008)]. The results reveal some intrinsic relation between quantumness of correlations and noncommutativity of states, and in particular, provide a characterization for zero quantum discord introduced by Ollivier and Zurek [Phys. Rev. Lett. 88, 017901 (2001)] from the broadcasting perspective. Furthermore, it is indicated that the distinction between the decomposition for general bipartite states and that for separable states might be useful in studying entanglement versus separability.


Journal of Physics A | 2002

An inequality for characteristic functions and its applications to uncertainty relations and the quantum Zeno effect

Shunlong Luo; Zhen Wang; Qiang Zhang

An inequality concerning characteristic functions is established. It is useful in studying zero neighbourhood behaviours of characteristic functions. The physical implications for the time-energy uncertainty relations and the quantum Zeno effect are indicated.

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Nan Li

Chinese Academy of Sciences

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Shuangshuang Fu

Chinese Academy of Sciences

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Qiang Zhang

City University of Hong Kong

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Jia-An Yan

Chinese Academy of Sciences

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Yuan Sun

Chinese Academy of Sciences

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Xuelian Cao

Huazhong University of Science and Technology

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C. H. Oh

National University of Singapore

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Yuanyuan Mao

Chinese Academy of Sciences

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Zhen-Yu Xu

Chinese Academy of Sciences

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