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arXiv 1901.04014quant-phhep-lat
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弯曲时空中中微子振荡和Dirac粒子动力学的量子模拟

Quantum Simulation of Neutrino Oscillation and Dirac Particle Dynamics in Curved Space-time

Arindam Mallick

摘要:

量子模拟是研究一般情况下Dirac粒子的重要方法。离散量子行走(DQW)是一种功能强大的量子模拟方案,可以在可控的桌面装置上实现。首先,我们发现传统的DQW不能精确地模拟Dirac元胞自动机(DCA),自由Dirac哈密顿(DH)的离散化理论。通过对分步DQW模型参数的选择,我们发现推广的分步DQW模型可以完全模拟单粒子DCA。接下来,我们质疑同样的SS-DQW是否可以模拟具有额外自由度的自由狄拉克粒子的动力学,例如除了自旋或手征之外的颜色,味道。一个这样的例子是中微子振荡。通过从U(2)提出的SS-DQW转移到U(6)提出的SS-DQW,我们模拟了中微子味跃迁的精确概率分布。我们进一步探讨了在背景势和时空曲率存在下模拟单粒子大质量DH。通过使用具有位置-时间依赖的硬币参数的SS-DQW,我们意识到它将在位置-时间的连续极限处给出无界的有效哈密顿量。因此,我们引入了一个修改版本的SS-DQW,它将产生一个有界的有效哈密顿量。在阿贝尔规范势和时空曲率存在的情况下,这种带有U(2)硬币操作的修正的SS-DQW产生了单粒子质量DH。在改进的SS-DQW中引入更高维的-U(N)硬币运算,我们可以在同一DH中包含非阿贝尔势。为了模拟弯曲时空和外势存在下的两粒子DH,我们采用了两粒子修正的SS-DQW,其中移位操作分别作用于每个粒子,硬币操作同时作用于两个粒子,包含各种相互作用。

英文摘要:

Quantum simulation is an important way to study the Dirac particles in a general situation. Discrete quantum walk (DQW), is a powerful quantum simulation scheme, and implementable in well controllable table-top set-ups. We first identify that the conventional DQW can't exactly simulate Dirac Cellular Automaton (DCA), a discretized theory of free Dirac Hamiltonian (DH). We found some choice of coin parameters of the split-step (SS) DQW, a generalization of DQW can fully simulate single-particle DCA. Next we question whether the same SS-DQW can simulate dynamics of free Dirac particle with extra degrees of freedom like colors, flavors besides the spin or chirality. One such example is Neutrino oscillation. By moving from the U(2) coined SS-DQW to the U(6) coined SS-DQW we have simulated the exact probability profile of Neutrino flavor transitions. We further probe towards simulating single particle massive DH in presence of background potentials and space-time curvature. By using a SS-DQW with position-time dependent coin parameters, and we realize that it will give us an unbounded effective Hamiltonian, at the continuum limit of position-time. So we have introduced a modified version of SS-DQW which will produce a bounded effective Hamiltonian. This modified SS-DQW with U(2) coin operations produces single-particle massive DH in presence of abelian gauge potentials and space-time curvature. Introducing higher dimensional---U(N) coin operations in the modified SS-DQW we can include non-abelian potentials in the same DH. In order to simulate two-particle DH in presence of curved space-time and external potentials, we have used two particle modified SS-DQW, where the shift operations act separately on each particle, the coin operations which act simultaneously on both particles contain all kinds of interactions.

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