Structural evolutions in the U(5)-O(6) quantum phase transition are investigated within the framework of the interacting boson model by comparing the two types of effective order parameters in the ground-state quantum phase transition and excited-state quantum phase transition. It is found that the monopole-pair transfer intensities can show critical behaviors not only in the ground-state quantum phase transition but also in the excited-state quantum phase transition. It is thus suggested that the main features of the ESQPT should persist in nuclear systems.Structural evolutions in the U(5)-O(6) quantum phase transition are investigated within the framework of the interacting boson model by comparing the two types of effective order parameters in the ground-state quantum phase transition and excited-state quantum phase transition. It is found that the monopole-pair transfer intensities can show critical behaviors not only in the ground-state quantum phase transition but also in the excited-state quantum phase transition. It is thus suggested that the main features of the ESQPT should persist in nuclear systems.

Zhongguo kexue. Wulixue Lixue TianwenxueSep 16, 20191 citation

Pairing correlations and transitions in nuclear systems

Aleksandar Belić, David J. Dean, Morten Hjorth-Jensen

Nuclear Physics AFeb 9, 20040 citations

Shannon entropy of optimized proton-neutron pair condensates

Shu-Yuan Liang, Yi Lu, Yang Lei +3 more

Proton-neutron pairing and like-nucleon pairing are two different facets of atomic nuclear configurations. While like-nucleon pair condensates manifest their superfluidic nature in semimagic nuclei, it is not absolutely clear if there exists a $T=0$ proton-neutron pair condensate phase in $N=Z$ nuclei. With an explicit formalism of general pair condensate with good particle numbers, we optimize proton-neutron pair condensates for all $N=Z$ nuclei between $^{16}\mathrm{O}$ and $^{100}\mathrm{Sn}$ , given shell model effective interactions. As comparison, we also optimize like-nucleon pair condensates for their semimagic isotones. Shannon entanglement entropy is a measurement of mixing among pair configurations, and can signal intrinsic phase transition. It turns out the like-nucleon pair condensates for semimagic nuclei have large entropies signaling an entangled phase, but the proton-neutron pair condensates end up not far from a Hartree-Fock solution with small entropy. With artificial pairing interaction strengths, we show that the general proton-neutron pair condensate can transit from an entangled $T=1$ phase to an entangled $T=0$ phase, i.e., pairing phase transition driven by external parameters. In the $T=0$ limit, the proton-neutron pair condensate optimized for $^{24}\mathrm{Mg}$ turns out to be a purely $T=0$ P-pair condensate with large entanglement entropy, although such cases may occur in cold atom systems, unlikely in atomic nuclei.Proton-neutron pairing and like-nucleon pairing are two different facets of atomic nuclear configurations. While like-nucleon pair condensates manifest their superfluidic nature in semimagic nuclei, it is not absolutely clear if there exists a $T=0$ proton-neutron pair condensate phase in $N=Z$ nuclei. With an explicit formalism of general pair condensate with good particle numbers, we optimize proton-neutron pair condensates for all $N=Z$ nuclei between $^{16}\mathrm{O}$ and $^{100}\mathrm{Sn}$, given shell model effective interactions. As comparison, we also optimize like-nucleon pair condensates for their semimagic isotones. Shannon entanglement entropy is a measurement of mixing among pair configurations, and can signal intrinsic phase transition. It turns out the like-nucleon pair condensates for semimagic nuclei have large entropies signaling an entangled phase, but the proton-neutron pair condensates end up not far from a Hartree-Fock solution with small entropy. With artificial pairing interaction strengths, we show that the general proton-neutron pair condensate can transit from an entangled $T=1$ phase to an entangled $T=0$ phase, i.e., pairing phase transition driven by external parameters. In the $T=0$ limit, the proton-neutron pair condensate optimized for $^{24}\mathrm{Mg}$ turns out to be a purely $T=0$ P-pair condensate with large entanglement entropy, although such cases may occur in cold atom systems, unlikely in atomic nuclei.

arXiv:2411.01439Physical Review CFeb 13, 20258 citations

Toward nuclear physics on a spin quantum simulator by detecting quantum phase transitions in the Agassi model

Yufang Feng, Xinyue Long, Hongfeng Liu +7 more

A central challenge in nuclear physics is understanding quantum many-body systems governed by the strong nuclear force. The inherent complexity of these systems, combined with the limitations of classical computational methods, underscores the need for new approaches to study nuclear structure and dynamics. Here, we demonstrate that a spin-based digital quantum simulator using nuclear magnetic resonance, where nuclear spins simulate interacting fermions, offers a powerful tool to address this challenge. As a first step, we experimentally simulate the Agassi model, which encapsulates the interplay between collective and single-particle behaviors in finite nuclei. By representing nucleons as both bosons (nucleon pairs) and fermions (individual unpaired nucleons), the Agassi model captures highly non-linear interactions and is particularly suited for studying nuclear phase transitions, such as those between spherical and deformed shapes. We experimentally measure the correlation function as an order parameter during the evolution of the many-body system, successfully detecting a quantum phase transition. Specifically, we observe a sharp transition between the symmetric phase and the broken symmetry phase. This work underscores the potential of quantum simulation as a transformative tool in nuclear physics, particularly for exploring complex quantum many-body systems with applications in nuclear structure and reaction dynamics.A central challenge in nuclear physics is understanding quantum many-body systems governed by the strong nuclear force. The inherent complexity of these systems, combined with the limitations of classical computational methods, underscores the need for new approaches to study nuclear structure and dynamics. Here, we demonstrate that a spin-based digital quantum simulator using nuclear magnetic resonance, where nuclear spins simulate interacting fermions, offers a powerful tool to address this challenge. As a first step, we experimentally simulate the Agassi model, which encapsulates the interplay between collective and single-particle behaviors in finite nuclei. By representing nucleons as both bosons (nucleon pairs) and fermions (individual unpaired nucleons), the Agassi model captures highly non-linear interactions and is particularly suited for studying nuclear phase transitions, such as those between spherical and deformed shapes. We experimentally measure the correlation function as an order parameter during the evolution of the many-body system, successfully detecting a quantum phase transition. Specifically, we observe a sharp transition between the symmetric phase and the broken symmetry phase. This work underscores the potential of quantum simulation as a transformative tool in nuclear physics, particularly for exploring complex quantum many-body systems with applications in nuclear structure and reaction dynamics.

Frontiers of PhysicsJan 1, 20251 citation

T=0

proton-neutron pair condensate phase in

N=Z

nuclei. With an explicit formalism of general pair condensate with good particle numbers, we optimize proton-neutron pair condensates for all

N=Z

nuclei between

^{16}\mathrm{O}

and

^{100}\mathrm{Sn}

, given shell model effective interactions. As comparison, we also optimize like-nucleon pair condensates for their semimagic isotones. Shannon entanglement entropy is a measurement of mixing among pair configurations, and can signal intrinsic phase transition. It turns out the like-nucleon pair condensates for semimagic nuclei have large entropies signaling an entangled phase, but the proton-neutron pair condensates end up not far from a Hartree-Fock solution with small entropy. With artificial pairing interaction strengths, we show that the general proton-neutron pair condensate can transit from an entangled

T=1

phase to an entangled

T=0

phase, i.e., pairing phase transition driven by external parameters. In the

T=0

limit, the proton-neutron pair condensate optimized for

^{24}\mathrm{Mg}

turns out to be a purely

T=0

P-pair condensate with large entanglement entropy, although such cases may occur in cold atom systems, unlikely in atomic nuclei.