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Scaling of entanglement and Berry phase in the Dicke model. F. Plastina, G. Liberti, R. Zaffino, F. Piperno (UNICAL) A. Carollo (IQOQI). Refs: G. Liberti, R. Zaffino, F. Piperno, F. P., Phys. Rev. A 73 032346 (2006) G. Liberti, F. P., F. Piperno, Phys. Rev. A 74 022324 (2006)
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Scaling of entanglement and Berry phase in the Dicke model F. Plastina, G. Liberti, R. Zaffino, F. Piperno (UNICAL) A. Carollo (IQOQI) Refs:G. Liberti, R. Zaffino, F. Piperno, F. P., Phys. Rev. A 73 032346 (2006) G. Liberti, F. P., F. Piperno, Phys. Rev. A 74 022324 (2006) F. P., G. Liberti, A. Carollo, Europhys. Lett. 76, 182 (2006)
Aim: • To describe the critical properties of entanglement and Berry phase near the super-radiant QPT; • To characterize the finite size scaling and obtain the critical exponents for both quantities. Outline: • Dicke model and its solution in the Born-Oppenheimer approach; • The thermodynamic limit and QPT; • Finite size scaling; • Entanglement and its scaling properties; • Berry phase and the scaling of its topological character.
Dicke model Collective coupling of N qubits to a boson mode Quantum Phase Transition: • Super-radiant phase: • Macroscopic mode occupation • Macroscopic magnetization
Adiabatic Limit: Born-Oppenheimer (in 5 steps) Adiabatic qubit Hamiltonian 1) Write the state in the form slow component fast component 2) Adiabatic qubit equation for a fixed value of the slow variable Q
3) The qubit eigenvalue gives an effective potential 4) Find the oscillator wave function
5) Observables: spin components Thermodynamic limit
Finite size scaling (Symanzik) Perturbation theory Critical exponent
Entanglement - a - Once the oscillator is traced out, the qubit state is completely separable - b – Entanglement of each qubit with the rest of the system Critical exponent
c – Entanglement of the oscillator • with the entire qubit register Thermodynamic limit Finite size system
Berry Phase Q-parametrized connection Thermodynamic limit Finite size