Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:quant-ph/0307169 · Physical Review A

Wehrl entropy, Lieb conjecture, and entanglement monotones

Florian Mintert, Karol Życzkowski

Published Feb 24, 2004• 43 citations
arXivHTMLPDF

Abstract

We propose to quantify the entanglement of pure states of $N\ifmmode\times\else\texttimes\fi{}N$ bipartite quantum systems by defining its Husimi distribution with respect to $\mathrm{SU}(N)\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(N)$ coherent states. The Wehrl entropy is minimal if and only if the analyzed pure state is separable. The excess of the Wehrl entropy is shown to be equal to the subentropy of the mixed state obtained by partial trace of the bipartite pure state. This quantity, as well as the generalized (R\'enyi) subentropies, are proved to be Schur concave, so they are entanglement monotones and may be used as alternative measures of entanglement.

DOI
10.1103/physreva.69.022317

Related papers

Wehrl entropy, entropic uncertainty relations, and entanglement

Stefan Floerchinger, Tobias Haas, Henrik Müller-Groeling

Wehrl entropy is an entropy associated with the Husimi quasiprobability distribution. We discuss how it can be used to formulate entropic uncertainty relations and for a quantification of entanglement in continuous variables. We show that the Wehrl-Lieb inequality is closer to equality than the usual Bia\l{}ynicki-Birula--Mycielski entropic uncertainty relation almost everywhere. Furthermore, we show how Wehrl mutual information can be used to obtain a measurable perfect witness for pure state bipartite entanglement, which additionally provides a lower bound on the entanglement entropy.

arXiv:2103.07229•Physical Review A•Jun 28, 2021•36 citations

Renyi-Wehrl entropies as measures of localization in phase space

Sven Gnutzmann, Karol Zyczkowski

Abstract. We generalize the concept of the Wehrl entropy of quantum states which gives a basis–independent measure of their localization in phase space. We discuss the minimal values and the typical values of these Rényi–Wehrl entropies for pure states for spin systems. According to Lieb’s conjecture the minimal values are provided by the spin coherent states. Though Lieb’s conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Rényi–Wehrl entropies averaged over the natural measure in the space of pure quantum states. 1.

•Jan 1, 2001•53 citations

Rényi-Wehrl entropies as measures of localization in phase space

Sven Gnutzmann∥, Karol Życzkowski

We generalize the concept of the Wehrl entropy of quantum states which gives a basis-independent measure of their localization in phase space. We discuss the minimal values and the typical values of these Rényi-Wehrl entropies for pure states for spin systems. According to Lieb's conjecture the minimal values are provided by the spin coherent states. Though Lieb's conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Rényi-Wehrl entropies averaged over the natural measure in the space of pure quantum states.

arXiv:quant-ph/0106016•Journal of Physics A Mathematical and General•Nov 21, 2001•85 citations

Wehrl entropy and entanglement complexity of quantum spin systems

Xu Chen, Yiqi Yu, Peng Zhang

Abstract The Wehrl entropy of a quantum state is the Shannon entropy of its coherent-state distribution function, and remains non-zero even for pure states. We investigate the relationship between this entropy and the many-particle quantum entanglement, for N spin-1/2 particles. Explicitly, we numerically calculate the Wehrl entropy of various N-particle ( 2 ⩽ N ⩽ 20 ) entangled pure states, with respect to the SU(2) ⊗ N coherent states. Our results show that for the large-N ( N ≳ 10 ) systems the Wehrl entropy of the highly chaotic entangled states (e.g. 2 − N / 2 ∑ s 1 , s 2 , … , s N =↑ , ↓ | s 1 , s 2 , … , s N ⟩ e − i ϕ s 1 , s 2 , … , s N , with ϕ s 1 , s 2 , … , s N being random angles) are substantially larger than that of the very regular entangled states (e.g. the Greenberger–Horne–Zeilinger state). Therefore, the Wehrl entropy can reflect the complexity of the quantum entanglement of many-body pure states, as proposed by Sugita (2003 J. Phys. A: Math. Gen. 36 9081). In particular, the Wehrl entropy per particle (WEPP) can be used as a quantitative description of this entanglement complexity. Unlike other quantities used to evaluate this complexity (e.g. the degree of entanglement between a subsystem and the other particles), the WEPP does not necessitate the division of the total system into two subsystems. We further demonstrate that many-body pure entangled states can be classified into three types, based on the behavior of the WEPP in the limit N → ∞ : states approaching that of a maximally mixed state

arXiv:2312.00611•New Journal of Physics•Dec 1, 2024•4 citations

Proof of the generalized Lieb-Wehrl conjecture for integer indices larger than one

Ayumu Sugita

Gnutzmann and Życzkowski have proposed the Rényi–Wehrl entropy as a generalization of the Wehrl entropy, and conjectured that its minimum is obtained for coherent states. We prove this conjecture for the Rényi index q = 2, 3, ... in the cases of compact semisimple Lie groups. A general formula for the minimum value is given.

arXiv:nlin/0208007•Journal of Physics A Mathematical and General•Oct 8, 2002•20 citations

An elementary approach to Wehrl-type entropy bounds in quantitative form

Fabio Nicola, Federico Riccardi, Paolo Tilli

We consider the problem of the stability (with sharp exponent) of the Lieb--Solovej inequality for symmetric $SU(N)$ coherent states, which was obtained only recently by the authors. Here, we propose an elementary proof of this result, based on reformulating the Wehrl-type entropy as a function defined on the unit sphere in $\mathbb{C}^d$, for some suitable $d$, and on some explicit (and somewhat surprising) computations.

math-phCross-listedarXiv:2512.04245•Dec 5, 2025•0 citations
We propose to quantify the entanglement of pure states of N\ifmmode×\else\texttimes\fiNN\ifmmode\times\else\texttimes\fi{}NN\ifmmode×\else\texttimes\fiN bipartite quantum systems by defining its Husimi distribution with respect to SU(N)\ifmmode×\else\texttimes\fiSU(N)\mathrm{SU}(N)\ifmmode\times\else\texttimes\fi{}\mathrm{SU}(N)SU(N)\ifmmode×\else\texttimes\fiSU(N) coherent states. The Wehrl entropy is minimal if and only if the analyzed pure state is separable. The excess of the Wehrl entropy is shown to be equal to the subentropy of the mixed state obtained by partial trace of the bipartite pure state. This quantity, as well as the generalized (R'enyi) subentropies, are proved to be Schur concave, so they are entanglement monotones and may be used as alternative measures of entanglement.
Wehrl entropy is an entropy associated with the Husimi quasiprobability distribution. We discuss how it can be used to formulate entropic uncertainty relations and for a quantification of entanglement in continuous variables. We show that the Wehrl-Lieb inequality is closer to equality than the usual Bia\l{}ynicki-Birula--Mycielski entropic uncertainty relation almost everywhere. Furthermore, we show how Wehrl mutual information can be used to obtain a measurable perfect witness for pure state bipartite entanglement, which additionally provides a lower bound on the entanglement entropy.
Abstract. We generalize the concept of the Wehrl entropy of quantum states which gives a basis–independent measure of their localization in phase space. We discuss the minimal values and the typical values of these Rényi–Wehrl entropies for pure states for spin systems. According to Lieb’s conjecture the minimal values are provided by the spin coherent states. Though Lieb’s conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Rényi–Wehrl entropies averaged over the natural measure in the space of pure quantum states. 1.
We generalize the concept of the Wehrl entropy of quantum states which gives a basis-independent measure of their localization in phase space. We discuss the minimal values and the typical values of these Rényi-Wehrl entropies for pure states for spin systems. According to Lieb's conjecture the minimal values are provided by the spin coherent states. Though Lieb's conjecture remains unproven, we give new proofs of partial results that may be generalized for other systems. We also investigate random pure states and calculate the mean Rényi-Wehrl entropies averaged over the natural measure in the space of pure quantum states.
Abstract The Wehrl entropy of a quantum state is the Shannon entropy of its coherent-state distribution function, and remains non-zero even for pure states. We investigate the relationship between this entropy and the many-particle quantum entanglement, for N spin-1/2 particles. Explicitly, we numerically calculate the Wehrl entropy of various N-particle ( 2 ⩽ N ⩽ 20 ) entangled pure states, with respect to the SU(2) ⊗ N coherent states. Our results show that for the large-N ( N ≳ 10 ) systems the Wehrl entropy of the highly chaotic entangled states (e.g. 2 − N / 2 ∑ s 1 , s 2 , … , s N =↑ , ↓ | s 1 , s 2 , … , s N ⟩ e − i ϕ s 1 , s 2 , … , s N , with ϕ s 1 , s 2 , … , s N being random angles) are substantially larger than that of the very regular entangled states (e.g. the Greenberger–Horne–Zeilinger state). Therefore, the Wehrl entropy can reflect the complexity of the quantum entanglement of many-body pure states, as proposed by Sugita (2003 J. Phys. A: Math. Gen. 36 9081). In particular, the Wehrl entropy per particle (WEPP) can be used as a quantitative description of this entanglement complexity. Unlike other quantities used to evaluate this complexity (e.g. the degree of entanglement between a subsystem and the other particles), the WEPP does not necessitate the division of the total system into two subsystems. We further demonstrate that many-body pure entangled states can be classified into three types, based on the behavior of the WEPP in the limit N → ∞ : states approaching that of a maximally mixed state
We consider the problem of the stability (with sharp exponent) of the Lieb--Solovej inequality for symmetric SU(N)SU(N)SU(N) coherent states, which was obtained only recently by the authors. Here, we propose an elementary proof of this result, based on reformulating the Wehrl-type entropy as a function defined on the unit sphere in Cd\mathbb{C}^dCd, for some suitable ddd, and on some explicit (and somewhat surprising) computations.