We show that radiative coupling between two multilevel atoms having near-degenerate states can produce new interference effects in spontaneous emission. We explicitly demonstrate this possibility by considering two identical V systems each having a pair of transition dipole matrix elements which are orthogonal to each other. We discuss in detail the origin of the new interference terms and their consequences. Such terms lead to the evolution of certain coherences and excitations which would not occur otherwise. The special choice of the orientation of the transition dipole matrix elements enables us to illustrate the significance of vacuum induced coherence in multi-atom multilevel systems. These coherences can be significant in energy transfer studies.
Quantum coherence, emerging from the 'superposition' of quantum states, is widely used in various information processing tasks. Recently, the resource theory of multilevel quantum coherence is attracting substantial attention. In this paper, we mainly study the deterministic transformations of resource pure states via free operations in the theoretical framework for multilevel coherence. We prove that any two multilevel coherent resource pure states can be interconverted with a nonzero probability via a completely positive and trace non-increasing $k$-coherence-preserving map. Meanwhile, we pr…
Quantifying multilevel coherence and multipartite correlation based on $α$-affinity
Hebei GEO University（河北地质大学）；Intelligent Sensor Network Engineering Research Center of Hebei Province, Hebei GEO University（河北省智能传感网络工程研究中心）；School of Mathematics and Statistics, Shangqiu Normal University（商丘师范学院数学与统计学院）
Driving Quantum Heat Engines Beyond Classical Limits through Multilevel Coherence
Institute for Quantum Science and Engineering, Texas A&M University（德克萨斯农工大学量子科学与工程研究所）；Okinawa Institute of Science and Technology Graduate University（冲绳科学技术大学院大学）；Baylor University（贝勒大学）；Princeton University（普林斯顿大学）
Quantum coherence is one of the clearest departures from classical physics, exhibited when a system is in a superposition of different basis states. Here the coherent superposition of three motional Fock states of a single trapped ion is experimentally certified, with a procedure provably robust against imperfect operation. As the motional state cannot be directly interrogated, our scheme uses an interference pattern generated by projective measurement of the coupled qubit state. The minimum number of coherently superposed states is inferred from a series of threshold values based on analysis …
Our work is based on the collision-induced coherence of two decay channels along two optical transitions.The quantum interference of pumping processes creates the dark state and the more atoms are pumped in this collision-induced dark state the stronger the suppression of the spontaneous emission. The efficiency of this suppression is quantified by putting it in comparison with the spontaneous emission on the ultraviolet transition which proceeds in a regular fashion. The branching ratio of these two(visible and ultraviolet) transitions is introduced as the effective measure of the degree of t…
Quantum coherence, present whenever a quantum system exists in a superposition of multiple classically distinct states, marks one of the fundamental departures from classical physics. Quantum coherence has recently been investigated rigorously within a resource-theoretic formalism. However, the finer-grained notion of multilevel coherence, which explicitly takes into account the number of superposed classical states, has remained relatively unexplored. A comprehensive analysis of multi-level coherence, which acts as the single-party analogue to multi-partite entanglement, is essential for unde…
Characterizing genuine quantum resources and determining operational rules for their manipulation are crucial steps to appraise possibilities and limitations of quantum technologies. Two such key resources are nonclassicality, manifested as quantum superposition between reference states of a single system, and entanglement, capturing quantum correlations among two or more subsystems. Here we present a general formalism for the conversion of nonclassicality into multipartite entanglement, showing that a faithful reversible transformation between the two resources is always possible within a pre…
Modified Bloch-Redfield Master Equation for Incoherent Excitation of Multilevel Quantum Systems
提出了一种计算与非相干光弱相互作用的多能级量子系统的密度矩阵随时间演化的有效理论方法。该方法结合了布洛赫-雷德菲尔德理论与单光子相干性的部分长期近似，导致在一个主方程，明确暴露依赖于跃迁速率和跃迁偶极矩之间的角度的能量基础。修正的布洛赫-雷德菲尔德主方程允许在非相干光照射下量子相干与非相干能量转移之间的明确区分。完全非相干制度的特点是正交跃迁偶极矩的能量基础，导致由相干自由保利型主方程的动力学演化。相干区要求能量基中存在非正交跃迁偶极矩，并导致噪声诱导的量子相干性和粒子数-相干耦合的产生。作为第一个应用，我们考虑了单基态非相干光激发下的激发态相干态的动力学，观察到了在小激发态分裂的情况下粒子数到相干态的转移和非平衡准稳态的形成。早期推导出的V型系统的分析表达式[Phys. Rev. Lett. 113，113601（2014）]被发现提供了在小分子和大分子限制下的多级激发态布居和相干态的几乎定量的描述。
We consider the single photon transistor in coupled cavity system of resonators interacting with multilevel superconducting artificial atom simultaneously. Effective single mode transformation is used for the diagonalization of the the hamiltonian and impedance matching in terms of the normal modes. Storage and transmission of the incident field are described by the interactions between the cavities controlling the atomic transitions of lowest lying states. Rabi splitting of vacuum induced multiphoton transitions is considered in input/output relations by the quadrature operators in the absenc…
Light induced processes in nature occur by irradiation with slowly turned-on incoherent light. The general case of time-dependent incoherent excitation is solved here analytically for V-type systems using a newly developed master equation method. Clear evidence emerges for the disappearance of radiatively induced coherence as turn-on times of the radiation exceed characteristic system times. The latter is the case, in nature, for all relevant dynamical time scales for other than nearly degenerate energy levels. We estimate that, in the absence of non-radiative relaxation and decoherence, turn-…
