Franchi Alessio, Rossini Davide, Vicari Ettore
Dipartimento di Fisica, Università di Pisa and INFN, Largo Pontecorvo 3, 56127 Pisa, Italy.
Phys Rev E. 2022 May;105(5-1):054111. doi: 10.1103/PhysRevE.105.054111.
We study the ground-state properties of a quantum sunburst model, composed of a quantum Ising spin ring in a transverse field, symmetrically coupled to a set of ancillary isolated qubits, to maintain a residual translation invariance and also a Z_{2} symmetry. The large-size limit is taken in two different ways: either by keeping the distance between any two neighboring ancillary qubits fixed or by fixing their number while increasing the ring size. Substantially different regimes emerge, depending on the various Hamiltonian parameters: For small energy scale δ of the ancillary subsystem and small ring-qubit interaction κ, we observe rapid and nonanalytic changes in proximity to the quantum transitions of the Ising ring, both first order and continuous, which can be carefully controlled by exploiting renormalization-group and finite-size scaling frameworks. Smoother behaviors are instead observed when keeping δ>0 fixed and in the Ising disordered phase. The effect of an increasing number n of ancillary spins turns out to scale proportionally to sqrt[n] for sufficiently large values of n.
我们研究了一种量子日冕模型的基态性质，该模型由处于横向场中的量子伊辛自旋环组成，对称地耦合到一组辅助孤立量子比特，以保持残余平移不变性以及(Z_{2})对称性。大尺寸极限通过两种不同方式取得：要么保持任意两个相邻辅助量子比特之间的距离固定，要么在增加环尺寸的同时固定它们的数量。根据各种哈密顿量参数，会出现截然不同的 regime：对于辅助子系统的小能量尺度(\delta)和小的环 - 量子比特相互作用(\kappa)，我们观察到在伊辛环的量子跃迁附近出现快速且非解析的变化，包括一阶和连续变化，这可以通过利用重整化群和有限尺寸标度框架来仔细控制。相反，当保持(\delta>0)固定且处于伊辛无序相时，会观察到更平滑的行为。对于足够大的辅助自旋数(n)，辅助自旋数增加的影响结果与(\sqrt{n})成比例缩放。
