Note that equations and expressions has been omitted here and is instead presented in the work. This thesis focuses on the geometric phase in pure and mixed quantum states. For the case of a pure quantum state, Berry's adiabatic approach (4.1.10) and Aharonov & Anandan's non-adiabatic generalization of Berry's approach (4.2.8) are included in this work. Mixed quantum state involves Uhlmanns approach (5.1.42), which is used extensively in Section 7 and Sjöqvist's et al. approach (5.2.22), used extensively in Section 6. Sjöqvist's approach states that the Uhlmann phase is an observable and provides the experimental groundworkusing an interferometer.􀀀This was later proven, by Du et al.[45] to reproduce experimental data (Figure 19) on page 56. The Uhlmann phase can be used to observe the behaviour of topological kinks. This was tested on 3 models, the Creutz-ladder, the Majorana chain andthe SSU-model. It is found that the Uhlmann phase is split into two regimes with the dividing parameter being the temperature. This temperature is called the critical temperature, Tc. If the temperatureis is below the critical temperature, the Uhlmann phase yields Π and if thetemperature is above the critical temperature, the Uhlmann phase yields zero.Note that equations and expressions has been omitted here and is instead presented in the work. This thesis focuses on the geometric phase in pure and mixed quantum states. For the case of a pure quantum state, Berry's adiabatic approach (4.1.10) and Aharonov & Anandan's non-adiabatic generalization of Berry's approach (4.2.8) are included in this work. Mixed quantum state involves Uhlmanns approach (5.1.42), which is used extensively in Section 7 and Sjöqvist's et al. approach (5.2.22), used extensively in Section 6. Sjöqvist's approach states that the Uhlmann phase is an observable and provides the experimental groundworkusing an interferometer.􀀀This was later proven, by Du et al.[45] to reproduce experimental data (Figure 19) on page 56. The Uhlmann phase can be used to observe the behaviour of topological kinks. This was tested on 3 models, the Creutz-ladder, the Majorana chain andthe SSU-model. It is found that the Uhlmann phase is split into two regimes with the dividing parameter being the temperature. This temperature is called the critical temperature, Tc. If the temperatureis is below the critical temperature, the Uhlmann phase yields Π and if thetemperature is above the critical temperature, the Uhlmann phase yields zero.

Jan 1, 20170 citations

Geometric phase and its applications to fundamental physics

Antonio Capolupo, Giuseppe Vitiello

We report on recent results showing that the geometric phase can be used as a tool in the analysis of many different physical systems, as mixed boson systems, CPT and CP violations, Unruh effects and thermal states. We show that the geometric phases appearing in the time evolution of mixed meson systems like $B_{s}^{0}-\bar{B}_{s}^{0}$ and the $K^{0}-\bar{K}^{0}$ are linked to the parameter $z$ describing the $CPT$ violation. A non zero phase difference between particle and antiparticle arises only in the presence of $CPT$ symmetry breaking. Then the geometric phase can represent a completely new test for the $CPT$ invariance. Moreover, we study the geometric phase of systems represented by mixed state and undergoing a nonunitary evolution and propose the realization of interferometers which can prove the existence of the Unruh effect and can allow very precise measurements of temperature. We are glad to dedicate this paper to Professor Gaetano Vilasi in the occasion of his 70th birthday.We report on recent results showing that the geometric phase can be used as a tool in the analysis of many different physical systems, as mixed boson systems, CPT and CP violations, Unruh effects and thermal states. We show that the geometric phases appearing in the time evolution of mixed meson systems like $B_{s}^{0}-\bar{B}_{s}^{0}$ and the $K^{0}-\bar{K}^{0}$ are linked to the parameter $z$ describing the $CPT$ violation. A non zero phase difference between particle and antiparticle arises only in the presence of $CPT$ symmetry breaking. Then the geometric phase can represent a completely new test for the $CPT$ invariance. Moreover, we study the geometric phase of systems represented by mixed state and undergoing a nonunitary evolution and propose the realization of interferometers which can prove the existence of the Unruh effect and can allow very precise measurements of temperature. We are glad to dedicate this paper to Professor Gaetano Vilasi in the occasion of his 70th birthday.

arXiv:1512.03265Dec 9, 20151 citation

The temperature dependent geometric phase

Zheng-Chuan Wang

Jan 1, 20260 citations

Mixed-state entanglement and phase transitions in Einstein-Born-Infeld massive gravity

Zhe Yang, Jian-Pin Wu, Peng Liu

We study mixed-state entanglement measures in Einstein-Born-Infeld (EBI) massive gravity theory, a model exhibiting both Hawking-Page phase transitions and effective metal-insulator transitions (MIT) at finite temperatures. Our comprehensive investigation reveals that the entanglement wedge cross-section (EWCS), a holographic probe of mixed-state entanglement structure, demonstrates distinctive properties in detecting phase transitions. For the effective MIT, we find that the higher-order terms of EWCS align closely with the crossover temperature, a feature not shared by holographic entanglement entropy (HEE). This sensitivity makes EWCS a complementary geometric tool for probing effective phase transitions at finite temperatures. In Hawking-Page phase transitions, we observe that all entanglement measures effectively diagnose both first-order and second-order phase transitions, with EWCS showing configuration-independent behavior. Importantly, we discover that all geometry-related quantities, including entanglement measures, demonstrate a universal critical exponent of 1/3 near the second-order phase transition point. This result suggests a fundamental connection between quantum information theory and critical phenomena in gravitational systems, and also highlights the potential of EWCS as a powerful probe for phase transitions.We study mixed-state entanglement measures in Einstein-Born-Infeld (EBI) massive gravity theory, a model exhibiting both Hawking-Page phase transitions and effective metal-insulator transitions (MIT) at finite temperatures. Our comprehensive investigation reveals that the entanglement wedge cross-section (EWCS), a holographic probe of mixed-state entanglement structure, demonstrates distinctive properties in detecting phase transitions. For the effective MIT, we find that the higher-order terms of EWCS align closely with the crossover temperature, a feature not shared by holographic entanglement entropy (HEE). This sensitivity makes EWCS a complementary geometric tool for probing effective phase transitions at finite temperatures. In Hawking-Page phase transitions, we observe that all entanglement measures effectively diagnose both first-order and second-order phase transitions, with EWCS showing configuration-independent behavior. Importantly, we discover that all geometry-related quantities, including entanglement measures, demonstrate a universal critical exponent of 1/3 near the second-order phase transition point. This result suggests a fundamental connection between quantum information theory and critical phenomena in gravitational systems, and also highlights the potential of EWCS as a powerful probe for phase transitions.

arXiv:2601.00071Dec 31, 20250 citations

B_{s}^{0}-\bar{B}_{s}^{0}

and the

K^{0}-\bar{K}^{0}

are linked to the parameter

z

describing the

CPT

violation. A non zero phase difference between particle and antiparticle arises only in the presence of

CPT

symmetry breaking. Then the geometric phase can represent a completely new test for the

CPT

invariance. Moreover, we study the geometric phase of systems represented by mixed state and undergoing a nonunitary evolution and propose the realization of interferometers which can prove the existence of the Unruh effect and can allow very precise measurements of temperature. We are glad to dedicate this paper to Professor Gaetano Vilasi in the occasion of his 70th birthday.