This comment on the Phys. Rev. A paper "Nonlinear quantum effects in electromagnetic radiation of a vortex electron" by Karlovets and Pupasov-Maximov [Phys. Rev. A 103, 12214 (2021)] addresses their criticism of the combined experimental and theoretical study "Observing the quantum wave nature of free electrons through spontaneous emission" by Remez et al, published in Phys. Rev. Lett. [Phys. Rev. Lett. 123, 060401 (2019)]. We show, by means of simple optical arguments as well as numerical simulations, that the criticism raised by Karlovets and Pupasov-Maximov regarding the experimental regime reported by Remez et al is false. Further, we discuss a necessary clarification for the theoretical derivations presented by Karlovets and Pupasov-Maximov, as they only hold for a certain experimental situation where the final state of the emitting electron is observed in coincidence with the emitted photon - which is not the common scenario in cathodoluminescence. Upon lifting the concerns regarding the experimental regime reported by Remez et al, and explicitly clarifying the electron post-selection, we believe that the paper by Karlovets and Pupasov-Maximov may constitute a valuable contribution to the problem of spontaneous emission by shaped electron wavefunctions, as it presents new expressions for the emission rates beyond the ubiquitous paraxial approximation.
Comment on "Generating a perfect quantum optical vortex"
在最近的一篇文章中，Banerji等人介绍了一种新的光的量子态，由于其与经典的完美涡旋光束的数学相似性，被称为完美量子光学涡旋态[Phys. Rev. A 94，053838（2016）]。这种状态是通过贝塞尔-高斯涡旋态的傅里叶变换获得的，作者声称这可以通过一个简单的透镜来实现。在这里，我们将证明这种说法是错误的，因为透镜不能修改与输入光学量子态相关的量子噪声分布，这必须由“有效透镜”来交换。
A missing angle-dependent prefactor in the wave functions for half-integer magnetic flux obtained in [Y. Aharonov and D. Bohm, Phys. Rev. 115, 485 (1959)] is supplied, without which the result is not single-valued. No physical conclusions of the paper are affected.
Comment on "Limits of the measurability of the local quantum electromagnetic-field amplitude"
有人认为，最近的重新分析的结果由Compagno和Escherico [Phys. Rev. A 57，1595（1998）]的玻尔-罗森菲尔德程序的电磁场的一个单一的时空平均分量的测量是不正确的，当现场测量时间短于所需的光穿过测量的测试机构。为此，时间平均的“自作用力”的测试机构，假设为简单的球形形状，评估的一般轨迹的一维求积允许的测试机构由Compagno和Atriico，并在封闭形式的限制阶状轨迹玻尔和Rosenfeld。
Structured vortex waves have numerous applications in optics, plasmonics, radio-wave technologies and acoustics. We present a theoretical study of a method for generating vortex states based on coherent superposition of waves from discrete elements of planar phased arrays, given limitations on an element number. Using Jacobi-Anger expansion, we analyze emerging vortex topologies and derive a constraint for the least number of elements needed to generate a vortex with a given leading-order topological charge.
Exact solutions of the Dirac equation, a system of four partial differential equations, are rare. The vast majority of them are for highly symmetric stationary systems. Moreover, only a handful of solutions for time dependent dynamics exists. Given the growing number of applications of high energy electron beams interacting with a variety of quantum systems in laser fields, novel methods for finding exact solutions to the Dirac equation are called for. We present a method for building up solutions to the Dirac equation employing a recently introduced approach for the description of spinorial f…
We argue that while the experiment of Remez et al. is interesting and its conclusions may well be correct, the observed lack of dependence of the measured distributions on the electron's transverse coherence length should have been expected for the parameters chosen. This is because for Smith-Purcell radiation it is the coherence length of a virtual photon that plays a role of the radiation formation width and not the entire electron's coherence length that can well be orders of magnitude larger. This is a common feature for all the radiation processes in which a photon is emitted not directly…
