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中国物理学会期刊

哈密顿量宇称-时间对称性的刻画

CSTR: 32037.14.aps.73.20230458

Depiction of Hamiltonian PT-symmetry

CSTR: 32037.14.aps.73.20230458
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  • 宇称-时间(PT)对称性理论描述了具有实能级的非厄密特哈密顿量, 在量子物理学和量子信息科学中起着重要作用, 是量子力学中活跃且重要的主题. 研究者们对如何描述哈密顿量的PT对称性的问题给予了高度关注. 本文基于PT对称理论和哈密顿量归一化特征函数, 提出了算子F的定义. 然后, 在找到算子CPT和算子F的对易子和反对易子的特性后, 给出了刻画了无量纲情况下哈密顿量的PT对称性的第一种方法. 进一步研究发现, 该方法还可以量化哈密顿量在无量纲情况下的PT对称性. 此外, 提出了另一种基于哈密顿量特征值实部和虚部来描述哈密顿量PT对称性的方法, 该方法仅用于判断哈密顿量是否具有PT对称性.

     

    The theory of PT-symmetry describes the non-hermitian Hamiltonian with real energy levels, which means that the Hamiltonian H is invariant neither under parity operator P, nor under time reversal operator T, PTH = H. Whether the Hamiltonian is real and symmetric is not a necessary condition for ensuring the fundamental axioms of quantum mechanics: real energy levels and unitary time evolution. The theory of PT-symmetry plays a significant role in studying quantum physics and quantum information science, Researchers have paid much attention to how to describe PT-symmetry of Hamiltonian. In the paper, we define operator F according to the PT-symmetry theory and the normalized eigenfunction of Hamiltonian. Then we first describe the PT-symmetry of Hamiltonian in dimensionless cases after finding the features of commutator and anti-commutator of operator CPT and operator F. Furthermore, we find that this method can also quantify the PT-symmetry of Hamiltonian in dimensionless case. I(CPT, F) = ||CPT, F||CPT represents the part of PT-symmetry broken, and J(CPT, F) = ||CPT, F||CPT represents the part of PT-symmetry. If I(CPT, F) = ||CPT, F||CPT = 0, Hamiltonian H is globally PT-symmetric. Once I(CPT, F) = ||CPT, F||CPT ≠ 0, Hamiltonian H is PT-symmetrically broken. In addition, we propose another method to describe PT-symmetry of Hamiltonian based on real and imaginary parts of eigenvalues of Hamiltonian, to judge whether the Hamiltonian is PT symmetric. ReF = 1/4||(CPTF+F)||CPT represents the sum of squares of real part of the eigenvalue En of Hamiltonian H, ImF = 1/4||(CPTFF)||CPT is the sum of imaginary part of the eigenvalue En of a Hamiltonian H. If ImF = 0, Hamiltonian H is globally PT-symmetric. Once ImF ≠ 0, Hamiltonian H is PT-symmetrically broken. ReF = 0 implies that Hamiltonian H is PT-asymmetric, but it is a sufficient condition, not necessary condition. The later is easier to realize in the experiment, but the studying conditions are tighter, and it further requires that CPT \phi_n (x) = \phi_n (x). If we only pay attention to whether PT-symmetry is broken, it is simpler to use the latter method. The former method is perhaps better to quantify the PT-symmetrically broken part and the part of local PT-symmetry.

     

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