We study a two-level model coupled to the electromagnetic vacuum and to an external classic electric field with fixed frequency. The amplitude of the external electric field is supposed to vary very slow in time. Garrison and Wright [{\it Phys. Lett.} {\bf A128} (1988) 177] used the non-hermitian Hamiltonian approach to study the adiabatic limit of this model and obtained that the probability of this two-level system to be in its upper level has an imaginary geometric phase. Using the master equation for describing the time evolution of the two-level system we obtain that the imaginary phase due to dissipative effects is time dependent, in opposition to Garrison and Wright result. The present results show that the non-hermitian hamiltonian method should not be used to discuss the nature of the imaginary phases in open systems.
The spontaneous emission of an excited two-level emitter driven by a strong classical coherent low-frequency electromagnetic field is investigated. We find that for relatively strong laser driving, multi-photon processes are induced, thereby opening additional decay channels for the atom. We analyze the interplay between the strong low-frequency driving and the interfering multiphoton decay channels, and discuss its implications for the spontaneous emission dynamics.
Spontaneous decay of an excited atom in a waveguide is essentially modified by the spatial structure of vacuum reservoir. This is particularly exciting in view of a range of applications for quantum information science. We found out that spontaneous decay can be incomplete, so the time dependence of the excited state population asymptotically approaches to a nonzero value, under the conditions when the atomic transition frequency is larger than the cutoff frequency of a waveguide and far from the vicinities of the cut-offs. Discovered effect is explained by the emergence of the dark state, whi…
Quantum simulation on emerging quantum hardware is a topic of intense interest. While many studies focus on computing ground state properties or simulating unitary dynamics of closed systems, open quantum systems are an interesting target of study owing to their ubiquity and rich physical behavior. However, their non-unitary dynamics are also not natural to simulate on digital quantum devices. Here, we report algorithms for the digital quantum simulation of the dynamics of open quantum systems governed by a Lindblad equation using adaptations of the quantum imaginary time evolution (QITE) algo…
Quantum local-field corrections and spontaneous decay
最近发展的方案[S.谢尔湖Knoll和D.- G. Welsch，Phys.Rev.A58，700（1998）]中的方法来计算标准虚球腔模型的量子局域场修正。只有在充分考虑极化噪声的情况下，电场和磁场局域场算符才与QED一致。结果表明，局域场中的极化涨落可以显著地改变自发衰变率，与经典局域场修正得到的结果相比。特别地，自发发射率强烈地依赖于局域场虚腔的半径。
In a previous paper [B. Deb and G. S. Agarwal, Phys. Rev. A 90, 063417 (2014)], it was theoretically shown that, magneto-optical manipulation of low energy scattering resonances and atom-molecule transitions could lead to the formation of a bound state in continuum (BIC), provided there is no spontaneous emission. We find that even an exceedingly small spontaneous decay from exited molecular states can spoil the BIC. In this paper, we show how to circumvent the detrimental effect of spontaneous emission by making use of vacuum-induced coherence (VIC) which results in the cancellation or suppre…
We present a high-rate projective measurement-based approach for controlling non-unitary evolution of a quantum chain of interacting spins. In this approach, we demonstrate that local measurement of a single external spin coupled to the chain can produce a spin polaron, which remains stable after the end of the measurement. This stability results from the fact that the Hilbert space of the chain contains a subspace of non-decaying states, stable during the nonunitary evolution. These states determine the resulting final state of the chain and long-term shape of the polaron. In addition to form…
Van der Waals interaction and spontaneous decay of an excited atom in a superlens-type geometry
在宏观量子电动力学的框架下，研究了由左手材料和理想镜组成的平面磁电两层系统附近受激二能级原子所经历的共振范德华势.结果表明，忽略材料的吸收导致非物理的结果，与发散值的潜在远离表面。在适当的条件下，该装置被发现具有表面附近的屏障，其可用于悬浮颗粒或用作捕获或冷却机制。最后，讨论了自发衰变问题[J.Kästel和M. Fleischhauer，Phys. Rev. A \textbf{68}，011804（R）（2005）]。不考虑吸收被证明是彻底伪造的衰变率的原子位置的依赖。
Comment on "Spontaneous collapse: A solution to the measurement problem and a source of the decay in mesonic systems"
在最近的一篇文章[Phys. Rev. A 94，052128（2016）]中，作者计算了两种塌缩模型对中性介子跃迁概率的预测。值得注意的是，他们声称找到了对衰变率的影响，并试图证明需要一个新的参数$θ(0)$来充分表征标准坍缩模型的噪声。这两种说法是不正确的，是由有缺陷的计算引起的。这篇评论准确地从主方程中导出了正确的转移概率，解释了如何以安全的方式微扰计算它们，并最终显示了原始文章作者的主要错误。
In this paper we discuss the use of the transition operator method for the theoretical description of a multi-qubit system in a one-dimensional waveguide. A general calculation has been performed for the N-qubit system, which was then applied to the case of spontaneous decay for one and two qubits. The probabilities of transitions in such systems, as well as the emission spectra, are investigated in detail.
On the basis of the general quantum microscopic theory we study the process of spontaneous decay of an excited atom in a dense and disordered ensemble of point-like impurity atoms embedded into transparent dielectric and located near a charged perfectly conducting surface. We have analyzed the simultaneous influence of the modified spatial structure of field modes near the conductive surface and the electric field on the character of interatomic dipoledipole interaction. This leads to the modification of the transition spectrum of an excited atom inside an ensemble and the spontaneous decay dy…
Scaling behavior of dissipative systems with imaginary gap closing
The Chinese University of Hong Kong Shenzhen Research Institute（香港中文大学深圳研究院）；Department of Physics, The Chinese University of Hong Kong（香港中文大学物理系）；State Key Laboratory of Quantum Information Technologies and Materials, The Chinese University of Hong Kong（香港中文大学量子信息技术与材料国家重点实验室）
Spontaneous decay of an excited atomic state is a fundamental process that originates from the interaction between matter and vacuum modes of the electromagnetic field. The rate of decay can thus be engineered by modifying the density of final states of the joint atom-photon system. Imposing suitable boundary conditions on the electromagnetic field has been shown to alter the density of vacuum modes near the atomic transition, resulting in modified atomic decay rates. Here we report the first experimental demonstration of suppression of atomic radiative decay by reducing the density of availab…
We analyze vacuum tunneling in quantum field theory in a general formalism by using the Wigner representation. In the standard instanton formalism, one usually approximates the initial false vacuum state by an eigenstate of the field operator, imposes Dirichlet boundary conditions on the initial field value, and evolves in imaginary time. This approach does not have an obvious physical interpretation. However, an alternative approach does have a physical interpretation: in quantum field theory, tunneling can happen via classical dynamics, seeded by initial quantum fluctuations in both the fiel…
We introduce a photonic nanostructure made of two dimensional materials that can lead to non-Markovian dynamics in the spontaneous emission of a nearby quantum emitter. Specifically, we investigate the spontaneous emission dynamics of a two-level quantum emitter with picosecond free-space decay time, modelling J-aggregates, close to a MoS$_2$ nanodisk. Reversible population dynamics in the quantum emitter is obtained when the emitter's frequency matches the frequency of an exciton-polariton resonance created by the nanodisk. When such isolated resonances exist, decaying Rabi oscillations may o…
Mixed Quantum-Classical Electrodynamics: Understanding Spontaneous Decay and Zero Point Energy
通过Maxwell-Liouville方程的半经典传播，对一维和三维电子二能级系统与电磁场的耦合动力学进行了数值模拟.我们考虑了三种混合量子经典动力学：经典路径近似（CPA），Eschlafest动力学和对称量子经典（SQC）动力学。CPA未能恢复对自发发射的一致描述。一个一致的“自发”发射可以从Escherifest动力学中获得--只要一个开始于电子叠加态。自发发射总是使用SQC动力学获得的。使用的SQC和Eschlafest框架，我们进一步计算的动态输入脉冲后，但在这里，我们发现非常不同的响应：SQC和Eschlafest动态偏离有时强烈的计算速度的衰减的瞬态激发态。然而，我们的工作证实了W. Miller [J.Chem.Phys.69，2188-2195，1978]认为，Escherfest动力学可以有效地描述自发发射的某些方面，并突出了用半经典力学研究光-物质相互作用的新可能性。
