quantum phase
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Science ◽  
2022 ◽  
Vol 375 (6577) ◽  
pp. 142-143
Author(s):  
Albert Roura

An atom interferometer measures the quantum phase due to gravitational time dilation


2022 ◽  
Author(s):  
Kaiyuan Cao ◽  
Ming Zhong ◽  
Peiqing Tong

Abstract We study the dynamical quantum phase transitions (DQPTs) in the XY chains with the Dzyaloshinskii-Moriya interaction and the XZY-YZX type of three-site interaction after a sudden quench. Both the models can be mapped to the spinless free fermion models by the Jordan-Wigner and Bogoliubov transformations with the form $H=\sum_{k}\varepsilon_{k}(\eta^†_{k}\eta_{k}-\frac{1}{2})$, where the quasiparticle excitation spectra $\varepsilon_{k}$ may be smaller than 0 for some $k$ and are asymmetrical ($\varepsilon_{k}\neq\varepsilon_{-k}$). It's found that the factors of Loschmidt echo equal 1 for some $k$ corresponding to the quasiparticle excitation spectra of the pre-quench Hamiltonian satisfying $\varepsilon_{k}\cdot\varepsilon_{-k}<0$, when the quench is from the gapless phase. By considering the quench from different ground states, we obtain the conditions for the occurrence of DQPTs for the general XY chains with gapless phase, and find that the DQPTs may not occur in the quench across the quantum phase transitions regardless of whether the quench is from the gapless phase to gapped phase or from the gapped phase to gapless phase. This is different from the DQPTs in the case of quench from the gapped phase to gapped phase, in which the DQPTs will always appear. Besides, we also analyze the different reasons for the absence of DQPTs in the quench from the gapless phase and the gapped phase. The conclusion can also be extended to the general quantum spin chains.


Science ◽  
2022 ◽  
Vol 375 (6576) ◽  
pp. 76-81
Author(s):  
Nikola Maksimovic ◽  
Daniel H. Eilbott ◽  
Tessa Cookmeyer ◽  
Fanghui Wan ◽  
Jan Rusz ◽  
...  

2022 ◽  
Vol 105 (1) ◽  
Author(s):  
N. Gavrielov ◽  
A. Leviatan ◽  
F. Iachello

2022 ◽  
Author(s):  
Wu Yusen ◽  
Bujiao Wu ◽  
Jingbo Wang ◽  
Xiao Yuan

Abstract The use of quantum computation to speed-up machine learning algorithms is among the most exciting prospective applications in the NISQ era. Here, we focus on the quantum phase learning problem, which is crucially important in understanding many-particle quantum systems. We prove that, under widely believed complexity theory assumptions, quantum phase learning problem cannot be efficiently solved by machine learning algorithms using classical resources and classical data. Whereas using quantum data, we prove the universality of quantum kernel Alphatron in efficiently predicting quantum phases, indicating clear quantum advantages in such learning problems. We numerically benchmark the algorithm for a variety of problems, including recognizing symmetry-protected topological phases and symmetry-broken phases. Our results highlight the capability of quantum machine learning in efficient prediction of quantum phases of many-particle systems.


2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Jamil Khalouf-Rivera ◽  
Miguel Carvajal ◽  
Francisco Perez-Bernal

We characterize excited state quantum phase transitions in the two dimensional limit of the vibron model with the quantum fidelity susceptibility, comparing the obtained results with the information provided by the participation ratio. As an application, we locate the eigenstate closest to the barrier to linearity and determine the linear or bent character of the different overtones for particular bending modes of six molecular species. We perform a fit and use the optimized eigenvalues and eigenstates in three cases and make use of recently published results for the other three cases.


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