Superradiant Quantum Phase Transition for an Exactly Solvable Two-Qubit Spin-Boson Model

Area of Science:

• Quantum mechanics
• Quantum optics
• Condensed matter physics

Background:

• The spin-boson model is a fundamental model in quantum mechanics describing the interaction between a quantum system and a bath.
• Interacting qubit systems are crucial for quantum computing and quantum information processing.
• Quantum phase transitions (QPTs) represent fundamental changes in the ground state of quantum systems.

Purpose of the Study:

• To analyze a specific spin-boson-like model with two interacting qubits.
• To investigate the possibility of exactly solving the model due to its inherent symmetry.
• To analytically identify and characterize quantum phase transitions within this system.

Main Methods:

• The study employs an exactly solvable model characterized by exchange symmetry between two spins.
• Explicit expressions for eigenstates and eigenenergies are derived.
• The analysis focuses on identifying abrupt changes in key quantum properties.

Main Results:

• The model is shown to be exactly solvable due to exchange symmetry.
• First-order quantum phase transitions are analytically identified.
• These transitions are linked to significant changes in two-spin concurrence, net spin magnetization, and mean photon number.

Conclusions:

• The analyzed two-qubit model provides an exactly solvable platform for studying quantum phase transitions.
• The identified QPTs are physically relevant, demonstrating abrupt changes in measurable quantum properties.
• This work contributes to the understanding of quantum phase transitions in interacting qubit systems.