scholarly journals Dynamical phase transitions at finite temperature from fidelity and interferometric Loschmidt echo induced metrics

2018 ◽  
Vol 97 (9) ◽  
Author(s):  
Bruno Mera ◽  
Chrysoula Vlachou ◽  
Nikola Paunković ◽  
Vítor R. Vieira ◽  
Oscar Viyuela
Keyword(s):  
Phase Transitions ◽  
Finite Temperature ◽  
Dynamical Phase ◽  
Dynamical Phase Transitions ◽  
Loschmidt Echo

scholarly journals Dynamical phase transitions and Loschmidt echo in the infinite-range XY model

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150160 ◽  
Author(s):  
Bojan Žunkovič ◽  
Alessandro Silva ◽  
Michele Fabrizio
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Order Parameter ◽  
Quantum Systems ◽  
Xy Model ◽  
Time Behaviour ◽  
Dynamical Phase ◽  
Dynamical Phase Transitions ◽  
Loschmidt Echo ◽  
Infinite Range

We compare two different notions of dynamical phase transitions in closed quantum systems. The first is identified through the time-averaged value of the equilibrium-order parameter, whereas the second corresponds to non-analyticities in the time behaviour of the Loschmidt echo. By exactly solving the dynamics of the infinite-range XY model, we show that in this model non-analyticities of the Loschmidt echo are not connected to standard dynamical phase transitions and are not robust against quantum fluctuations. Furthermore, we show that the existence of either of the two dynamical transitions is not necessarily connected to the equilibrium quantum phase transition.

scholarly journals Probing dynamical phase transitions with a superconducting quantum simulator

2020 ◽  
Vol 6 (25) ◽  
pp. eaba4935
Author(s):  
Kai Xu ◽  
Zheng-Hang Sun ◽  
Wuxin Liu ◽  
Yu-Ran Zhang ◽  
Hekang Li ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Quantum Limit ◽  
Single Shot ◽  
Many Body ◽  
Dynamical Phase Transition ◽  
Dynamical Phase ◽  
Dynamical Phase Transitions ◽  
Quantum Simulator ◽  
Many Body Systems ◽  
Loschmidt Echo

Nonequilibrium quantum many-body systems, which are difficult to study via classical computation, have attracted wide interest. Quantum simulation can provide insights into these problems. Here, using a programmable quantum simulator with 16 all-to-all connected superconducting qubits, we investigate the dynamical phase transition in the Lipkin-Meshkov-Glick model with a quenched transverse field. Clear signatures of dynamical phase transitions, merging different concepts of dynamical criticality, are observed by measuring the nonequilibrium order parameter, nonlocal correlations, and the Loschmidt echo. Moreover, near the dynamical critical point, we obtain a spin squeezing of −7.0 ± 0.8 dB, showing multipartite entanglement, useful for measurements with precision fivefold beyond the standard quantum limit. On the basis of the capability of entangling qubits simultaneously and the accurate single-shot readout of multiqubit states, this superconducting quantum simulator can be used to study other problems in nonequilibrium quantum many-body systems, such as thermalization, many-body localization, and emergent phenomena in periodically driven systems.

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