Rouse Dominic M, Lovett Brendon W, Gauger Erik M, Westerberg Niclas
SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS, UK.
SUPA, Institute of Photonics and Quantum Sciences, Heriot-Watt University, Edinburgh, EH14 4AS, UK.
Sci Rep. 2021 Feb 19;11(1):4281. doi: 10.1038/s41598-021-83214-z.
Systems of interacting charges and fields are ubiquitous in physics. Recently, it has been shown that Hamiltonians derived using different gauges can yield different physical results when matter degrees of freedom are truncated to a few low-lying energy eigenstates. This effect is particularly prominent in the ultra-strong coupling regime. Such ambiguities arise because transformations reshuffle the partition between light and matter degrees of freedom and so level truncation is a gauge dependent approximation. To avoid this gauge ambiguity, we redefine the electromagnetic fields in terms of potentials for which the resulting canonical momenta and Hamiltonian are explicitly unchanged by the gauge choice of this theory. Instead the light/matter partition is assigned by the intuitive choice of separating an electric field between displacement and polarisation contributions. This approach is an attractive choice in typical cavity quantum electrodynamics situations.
相互作用的电荷和场的系统在物理学中无处不在。最近，研究表明，当物质自由度被截断为几个低能本征态时，使用不同规范导出的哈密顿量会产生不同的物理结果。这种效应在超强耦合 regime 中尤为显著。出现这种模糊性是因为变换会重新排列光和物质自由度之间的划分，因此能级截断是一种依赖于规范的近似。为了避免这种规范模糊性，我们根据势重新定义电磁场，对于这些势，由此产生的正则动量和哈密顿量不会因该理论的规范选择而明确改变。相反，光/物质划分是通过将电场在位移和极化贡献之间进行分离的直观选择来分配的。这种方法在典型的腔量子电动力学情况中是一个有吸引力的选择。
