Stochastic control of quantum coherence
Stefano Mancini, David Vitali, Paolo Tombesi, Rodolfo Bonifacio
系统参数的随机调制的应用通常增加退相干效应。在这里，我们将展示如何，采用适当的随机调制，而是有可能保持系统的量子相干性。
The application of a random modulation of a system parameter usually increases decoherence effects. Here we show how, employing an appropriate stochastic modulation, it is instead possible to preserve the quantum coherence of a system.
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In this paper, we address the issue of enhancing coherence of a state under stochastic strictly incoherent operations. Based on the $l_1$ norm of coherence, we obtain the maximal value of coherence that can be achieved for a state undergoing a stochastic strictly incoherent operation and the maximal probability of obtaining the maximal coherence. Our findings indicate that a pure state can be transformed into a maximally coherent state under a stochastic strictly incoherent operation if and only if all the components of the pure state are nonzero while a mixed state can never be transformed in…
The resource theory of coherence studies the operational value of superpositions in quantum technologies. A key question in this theory concerns the efficiency of manipulation and interconversion of this resource. Here we solve this question completely for mixed states of qubits by determining the optimal probabilities for mixed state conversions via stochastic incoherent operations. This implies new lower bounds on the asymptotic state conversion rate between mixed single-qubit states which in some cases is proven to be tight. Furthermore, we obtain the minimal distillable coherence for given…
Coherence properties of the stochastic oscillator
讨论了一个具有随机频率的振子作为评价物理系统的量子相干性的模型。它被发现，跳跃统计的选择必须小心考虑，如果要避免非物理后果。我们研究这样一个模型，评估它所导致的阻尼，退相干率和相关性，它导致的状态和渐近长时间的属性。讨论了初始态的选择及其对关联时间演化的影响。
Dissipation induced coherence and stochastic resonance of an open two-mode Bose-Einstein condensate
讨论了双阱中玻色-爱因斯坦凝聚体在相位噪声和粒子损失作用下的动力学行为。弱相互作用凝聚体的相位相干性，实验测量通过在干涉实验中的对比度，以及对外部驱动的响应成为最大的耗散率匹配系统的固有时间尺度的有限值。这可以理解为多粒子系统的随机共振。甚至更强的效果时，观察到的耗散行为与强粒子间的相互作用，几乎完全恢复冷凝物的纯度和增加的相位相干性显着。我们的理论结果得到了蒙特卡罗模拟的支持，这表明了良好的定性协议，并提供了一个微观解释所观察到的随机共振效应。
The interference pattern in electron double-slit diffraction is a hallmark of quantum mechanics. A long standing question for stochastic electrodynamics (SED) is whether or not it is capable of reproducing such effects, as interference is a manifestation of quantum coherence. In this study, we use excited harmonic oscillators to directly test this quantum feature in SED. We use two counter-propagating dichromatic laser pulses to promote a ground-state harmonic oscillator to a squeezed Schrödinger cat state. Upon recombination of the two well-separated wavepackets, an interference pattern emerg…
We propose the generalized stochastic Liouville equation to investigate the coherent dynamics in single molecule systems coupled to environments which exhibit both nonstationary and non-Markovian features. The generalized stochastic Liouville equation contains a generalized memory kernel associated with both the intrinsic system Hamiltonian and the non-Markovian features of the environmental noise, which returns to the well-known framework established by Kubo in the limit case that the environmental noise is stationary and memoryless. The coherence of the quantum system can be derived by means…
Control momentum entanglement with atomic spontaneously generated coherence
利用原子自发产生的相干性，提出了一种利用原子内部相干性来相干控制原子-光子动量纠缠的新方案。提出了一种新的“动量相位纠缠”现象，并发现在一定条件下，这种方案可以产生超高的动量纠缠.
Non-Holonomic Control III : Coherence Protection by the Quantum Zeno Effect and Non-Holonomic Control
在本文中，我们提出了一个相干性保护方法的基础上的多维推广的量子芝诺效应，以及从编码理论的想法。非完整控制技术作为一种物理工具，使其有效的实施。考虑了小量子系统和大量子系统的两种极限情况。
Coherence rephasing combined with spin-wave storage using chirped control pulses
基于光子回波的光量子存储方案通常采用中间步骤将光相干态转换为自旋相干态以获得更长的存储时间。我们分析了一个方案，使用三个相同的啁啾控制脉冲的相干重定相在一个非均匀加宽的三能级$Λ$系统的系综。脉冲诱导的绝热制度中的原子布居的循环排列。由信号脉冲产生的光相干性在中间时间间隔被存储为自旋相干性，并且当系综返回到初始状态时被重新定相以用于回波发射。当介质被反转时，在可能的部分重新定相期间的回波发射可以通过适当选择控制脉冲波矢量来抑制。我们表明，该计划的工作在一个光学密集的合奏，尽管在传播过程中控制脉冲失真。它方便地集成到存储方案的基础上的原子相干态的第二次重新定相的自旋波存储步骤。
Stabilizing qubit coherence via tracking-control
我们考虑的问题，稳定的相干性的一个单一的量子比特的马尔可夫消相干，通过应用控制哈密顿量，没有任何额外的资源。在这种情况下，既不应用量子纠错/避免，也不应用动态解耦。我们表明，使用跟踪控制，即，控制场对量子比特状态的调节，可以在有限的持续时间内保持相干性，直到控制场发散。
In quantum mechanics, photonic de Broglie waves have been understood as a unique property of quantum mechanics satisfying the complementarity between particle and wave natures of light, where the photonic de Broglie wavelength is inversely proportional to the number of entangled photons acting on a beam splitter. Very recently, the heart of nonclassical feature of photon bunching on a beam splitter was newly interpreted using pure wave nature of coherence optics [arXiv:1911.07174v2], paving a road to unconditionally secured classical key distribution [arXiv:1807.04233v3]. Here, Mach-Zehnder in…
State-Constrained Optimal Control for Coherence Preservation in Multi-Level Open Quantum Systems
本文研究多能级开放量子系统的量子相干性最优控制，基于Lindblad主方程提出能量最小化框架，结合Gamkrelidze形式的Pontryagin极小值原理与状态约束，在马尔可夫退相干下有效维持三能级系统的相干性。
Non-Holonomic Control IV : Coherence Protection in a Rubidium isotope
在本文中，我们提出了一个实际应用的一致性保护方法在前一篇文章中提出的。在铷同位素的两个自旋状态上编码的信息量子比特被保护免受电场和磁场的作用。
The unitary generation of coherence from an incoherent thermal state is investigated. We consider a completely controllable Hamiltonian allowing to generate all possible unitary transformations. Optimizing the unitary control to achieve maximum coherence leads to a micro-canonical energy distribution on the diagonal energy representation. We demonstrate such a control scenario starting from a Hamiltonian utilizing optimal control theory for unitary targets. Generating coherence from an incoherent initial state always costs external work. By constraining the amount of work invested by the contr…
Coherence control for qubits
我们研究了在比特翻转噪声的影响下，外部驱动场对量子比特相干特性的影响。在存在驱动的情况下，考虑了两种典型的情况：（i）导致在所谓的隧穿相干破坏中适当选择参数的场，以及（ii）与静态量子比特哈密顿量交换的场。在每种情况下，我们给高频驱动的相干时间的下限。这揭示了外场可用于相干稳定的条件。
Ponderomotive Control of Quantum Macroscopic Coherence
结果表明，由于辐射压力的作用，在具有振荡壁的谐振腔中可以产生薛定谔猫态。通过引入新的猫态，考虑了量子宏观相干性的光机控制及其探测。由于环境与这个非线性系统的耦合的影响被认为是开发一个运营商微扰程序来解决场模密度运营商的主方程。
On-demand control of photon echoes far exceeding the spin coherence constraint via coherence swapping between optical and spin transitions
在传统的受激（三脉冲）光子回波中，利用按需相干转换，在掺稀土Pr ~（3+）的Y_2SiO_5中观察到了超长、超高效的光子存储，存储时间延长了几个数量级，恢复效率提高了50倍。与应用于双脉冲光子回波的相同方法进行重定相停止相比，在受激光子回波中使用光谱光栅提供了光学和自旋状态之间的相位无关的相干转换。最终实现了一个超长的自旋布居衰变相关的光子存储协议，通过应用光学锁定的光谱光栅在传统的受激光子回波。目前在光子存储时间和检索效率方面的突破为利用量子中继器进行长距离量子通信打开了大门。
Quantum coherence as randomness under classical control
针对经典控制隐藏的量子设备，提出基于半定规划层次结构的完整且高效的相干性认证方法，并应用于量子信道相干性保持能力的判定。
Device-independent Verification of Quantum Coherence without Quantum Control
本研究突破传统相干性验证需量子态控制的限制，将Bell理论拓展至多源场景构建设备无关相干性模型，提出GHZ型佯谬验证相干载体特性，并通过双光子纠缠态实验实现空间量子叠加的局域测量见证。
Quantum coherence, a basic feature of quantum mechanics residing in superpositions of quantum states, is a resource for quantum information processing. Coherence emerges in a fundamentally different way for nonidentical and identical particles, in that for the latter a unique contribution exists linked to indistinguishability which cannot occur for nonidentical particles. We experimentally demonstrate by an optical setup this additional contribution to quantum coherence, showing that its amount directly depends on the degree of indistinguishability and exploiting it to run a quantum phase disc…
Collapse and revival of quantum coherence for a harmonic oscillator interacting with a classical fluctuating environment
研究了量子系统与经典随机场描述的噪声涨落环境相互作用的非经典动力学。作为一个典型的例子，我们考虑一个谐振子最初准备在一个最大的非经典状态，例如一个Fock数状态或薛定谔类猫状态，然后耦合到共振或非共振的外部场。随机建模使我们能够描述退相干动力学，而无需诉诸近似的量子主方程，并以受控的方式引入非马尔可夫效应。通过对不同非经典性判据的详细比较和对退相干时间的深入分析，揭示了一个丰富的现象学，其主要特征可以概括为：（1）经典记忆效应增加了量子相干性的生存时间;（2）系统的固有频率与经典场的中心频率之间的失谐引起了量子相干性的恢复。
Coherence distillation is a basic information-theoretic task in the resource theory of coherence. In this paper, we present the necessary and sufficient conditions under which a mixed state can be distilled into a pure coherent state via stochastic incoherent operations (sIOs). With the help of this result, we further show the following: (i) Any $2$-dimensional coherent state is distillable via sIOs if and only if it is a pure coherent state; (ii) a state $ρ$ is n-distillable via sIOs if and only if it is 1-distillable; and (iii) the set of distillable states via stochastic maximally incoheren…
Simultaneous control of populations and coherence phase of open two-level quantum systems with a single pulse
本文提出利用单一脉冲同时控制开放双能级量子系统的粒子数和相干相位，通过解析方法实现对系统动力学的精确调控。
Limits on Preserving Quantum Coherence using Multi-Pulse Control
我们探讨的物理限制脉冲动态解耦方法的退相干控制所确定的有限的时间资源。通过聚焦于由任意序列的$π$ -脉冲控制的消相干量子比特，我们建立了一个非微扰的定量上限，以达到指定的最大脉冲速率和噪声谱带宽的相干性。我们介绍了数字优化的控制“带宽适应”的序列，饱和的性能界限，并显示它们如何优于现有的序列在一个现实的激子量子位系统的时间约束是显着的。作为一个副产品，我们的分析加强了不可能的容错精度阈值的一般开放量子系统下的纯粹可逆的错误控制。
We study the remote creation of the polarization and intensity of the first-order coherence (or coherence intensity) in long spin-1/2 chains with one qubit sender and receiver. Therewith we use a physically motivated initial condition with the pure state of the sender and the thermodynamical equilibrium state of the other nodes. The main part of the creatable region is a one-to-one map of the initial-state (control) parameters, except the small subregion twice covered by the control parameters, which appears owing to the chosen initial state. The polarization and coherence intensity behave dif…
Coherence Control of Adiabatic Decoherence in a Three-level Atom with Lambda Configuration
本文研究了利用bang-bang控制技术抑制$Λ$组态三能级原子的绝热退相干。给出了解耦的Bang-Bang操作组，并编程实现了周期性射频孪生脉冲序列的控制过程。此外，我们还研究了非理想情况下的绝热退相干过程，建立了有效抑制绝热退相干的条件。
The origin of non-classicality in physical systems and its connection to distinctly quantum features such as entanglement and coherence is a central question in quantum physics. This work analyses this question theoretically and experimentally, linking quantitatively non-classicality with quantum coherence. On the theoretical front, we show when the coherence of an observable is linearly related to the degree of violation of the Kolmogorov condition, which quantifies the deviation from any classical (non-invasive) explanation of the multi-time statistics. Experimentally, we probe this connecti…
Phase Coherence and Control of Stored Photonic Information
我们报告演示的相位相干性和控制最近开发的“光存储”技术。具体来说，我们使用一个脉冲磁场来改变原子自旋激发的相位，这是由于光脉冲在温暖的Rb蒸汽中减速和储存。然后，我们将自旋激发转换回光，并在光学干涉测量中检测所产生的相移。光子态在物质中的相干存储对于实际实现量子信息处理中的许多基本概念是必不可少的。
Electric control of collective atomic coherence in an Erbium doped solid
我们展示了快速和准确的控制集体原子相干性的演变在掺铒固体使用外部电场。这是通过使用电场梯度和线性斯塔克效应控制在1536 nm处发射的铒离子的非均匀加宽来实现的。原子相干性的操纵的特征在于在光激发之后由样品发射的集体自发发射（光自由感应衰减），其不需要任何原子的先前准备。我们发现，由电场控制的原子的退相和再定相导致光学自由感应衰减的崩溃和复苏。我们的研究结果表明，使用外部电场不会引入任何实质性的额外的退相干，并使集体原子相干性的操作具有非常高的精度上的时间尺度上的几十ns。这为光子量子态存储和量子态操作提供了一个有趣的资源。
Quantum walks in dynamically-disordered networks have become an invaluable tool for understanding the physics of open quantum systems. In this work, we introduce a novel approach to describe the dynamics of indistinguishable particles in noisy quantum networks. By making use of stochastic calculus, we derive a master equation for the propagation of two non-interacting correlated particles in tight-binding networks affected by off-diagonal dynamical disorder. We show that the presence of noise in the couplings of a quantum network creates a pure-dephasing-like process that destroys all coherenc…
Coherence-preserving trap architecture for long-term control of giant Rydberg atoms
我们提出了一种方法来捕获一个单一的里德伯原子，使其长寿命，并保持一个内部的连贯性，在时间尺度达到分钟的范围。我们建议使用精心设计的电场陷阱，抑制自发发射的非共振导电结构，并通过使用外部微波场的原子能量的剪裁保持内部相干性。我们彻底查明并说明了许多不完美的原因，以便在每一步验证我们的建议的现实性。
The extension of the spin coherence times is a crucial issue for quantum information and quantum sensing. In solid state systems, suppressing noises with various techniques have been demonstrated. On the other hand, an electrical control for suppression is important toward individual controls of on-chip quantum information devices. Here we show the electrical control for extension of the spin coherence times of 40 nm-deep ion-implanted single nitrogen vacancy center spins in diamond by suppressing magnetic noises. We applied 120 V DC across two contacts spaced by 10 micrometers. The spin coher…
Induced Coherence in Quantum and Classical Interferometry: Origin and Control
本文证明量子诱导相干干涉仪中三重关系成立，经典配置恢复二象性不等式，并探索相干性与纠缠的起源及控制方法，揭示路径不可区分性的互补作用。
Sub-Riemannian Geometry and Time Optimal Control of Three Spin Systems: Quantum Gates and Coherence Transfer
在核磁共振光谱学中的许多相干转移实验，涉及耦合自旋网络，使用临时自旋去耦来产生所需的有效哈密顿量。在本文中，我们表明，显着的时间可以节省在产生一个有效的哈密顿量，如果避免自旋去耦。我们提供了时间最优脉冲序列产生一类重要的有效哈密顿在三个自旋网络。这些有效的哈密顿量对于核磁共振量子计算中的相干传输实验和量子逻辑门的实现是有用的。它表明，计算这些时间最优的脉冲序列可以减少到几何问题，涉及计算齐次空间上的次黎曼测地线。
Quantum states transformation under free operations plays a central role in the resource theory of coherence. In this paper, we investigate the transformation from a mixed coherent state into a pure one by using both incoherent operations and stochastic incoherent operations. We show that contrary to the strictly incoherent operations and the stochastic strictly incoherent operations, both the incoherent operations and the stochastic incoherent operations can increase the dimension of the maximal pure coherent subspace of a state. This means that the incoherent operations are generally stronge…
We show how the dispersive regime of the Jaynes-Cummings model may serve as a valuable tool to the study of open quantum systems. We employ it in a bottom-up approach to build an environment that preserves qubit energy and induces varied coherence dynamics. We then present the derivation of a compact expression for the qubit coherence, applied here to the case of a finite number of thermally populated modes in the environment. We also discuss how the model parameters can be adjusted to facilitate the production of short-time monotonic decay (STMD) of the qubit coherence. Our results provide a …
Resource theory of quantum coherence originated like entanglement in quantum information theory. However, still now proper classification of quantum states is missing under coherence. In this work, we have provided a classification of states under local incoherent operations. We have succeeded in deriving the necessary and sufficient condition for which two pure multipartite states are equivalent under stochastic local incoherent operations and classical communications (SLICC) and local incoherent operations and classical communications (LICC). In particular, we have succeeded in characterizin…
Kitaev's 0-$π$ qubit encodes quantum information in two protected, near-degenerate states of a superconducting quantum circuit. In a recent work, we have shown that the coherence times of a realistic 0-$π$ device can surpass that of today's best superconducting qubits [Groszkowski et al., New Journal of Physics 20 043053 (2018)]. Here we address controllability of the 0-$π$ qubit. Specifically, we investigate the potential for dispersive control and readout, and introduce a new, fast and high-fidelity single-qubit gate that can interpolate smoothly between logical X and Z. We characterize the …
A coherence method generating macroscopic quantum features using polarization-basis control and its projection measurements of laser light
本文提出纯相干方法，通过偏振基控制和线性光学投影测量，使常规激光的正交偏振光对具备不可区分性，从而产生宏观量子特征并揭示 Bell 态所需的固定相位条件。
Exact Stochastic Unraveling of an Optical Coherence Dynamics by Cumulant Expansion
提出并实现了一个计算开放量子系统动力学的数值精确Monte Carlo方法。该方法包括一个蒙特-卡罗总结的微扰展开的轨迹在刘维相空间相对于分子的激发态之间的耦合。轨迹加权的基础上的二阶累积展开的环境演变的复退相干因子。该方法可用于由一般关联函数和任意耦合强度表征的任意环境。它对谐波环境是形式上精确的，并且可以在任意温度下使用。用所提出的方法计算了光激发的Frenkel激子二聚体的时间演化，它代表分子激子与电荷转移态的相互作用。我们计算了密度矩阵和线性吸收谱的光学相干元素的演化，并与标准模拟方法的预测结果进行了比较。
Time-Optimal Transfer of Coherence
我们提供了精确的分析解决方案的时间最佳转移的相干性从一个自旋极化的三线性伊辛链的三倍相干性与固定的能量可用，并受到本地控制的一个不可忽略的时间成本的问题。转移的时间是最佳的，并与以前的数值结果假设瞬时局部控制一致。
The manipulation of quantum coherence is one of the principal issues in the resource theory of coherence, with two critical topics being the purification and enhancement of coherence. Here, we present two no-go theorems for the deterministic purification of coherence and the probabilistic enhancement of coherence, respectively. Specifically, we prove that a quantum state cannot be deterministically purified if it can be expressed as a convex combination of an incoherent state and a coherent state. Besides, we give an easy-to-verified sufficient and necessary condition to determine whether a st…
Coherence protection by the quantum Zeno effect and non-holonomic control in a Rydberg Rubidium isotope
保护开放量子系统的相干性不受其环境的影响是一个非常热门的问题。本文提出了一种方案，它保护一般量子系统不受任意不受控制的幺正演化的作用。该方法的灵感来自于标准纠错（附加、编码和解码）和量子芝诺效应的思想。我们的方法在一个简单的原子系统，即铷同位素的教学示范，提出。
Ground State Quantum Coherences: from Quantum Beats to Strong Control
二阶关联揭示了双模腔QED系统非驱动模上相干基态叠加的量子拍频。连续驱动由于瑞利散射而引起退相干。我们通过反馈来控制这一点，并探索后选择技术来提取特定的行为。
In this paper for the first time, we construct quantum analogs starting from classical stochastic processes, by replacing random which path decisions with superpositions of all paths. This procedure typically leads to non-unitary quantum evolution, where coherences are continuously generated and destroyed. In spite of their transient nature, these coherences can change the scaling behavior of classical observables. Using the zero temperature Glauber dynamics in a linear Ising spin chain, we find quantum analogs with different domain growth exponents. In some cases, this exponent is even smalle…
Coherent Control of Population and Quantum Coherence in Superconducting Circuits
本文探讨了在超导电路中通过相干控制实现量子能级人口和相干的突破性进展。
Here, we study a minimal model, the three-level V system coupled to two heat baths, and investigate the role of quantum coherences in heat transport in both the transient regime and in the nonequilibrium steady-state. In our model, energy is exchanged between the baths through two parallel pathways, which can be made distinct through the nondegeneracy of excited levels (energy splitting $Δ$) and a control parameter $α$, which adjusts the strength of one of the arms. Using a nonsecular quantum master equation of Redfield form, we succeed in deriving closed-form expressions for the quantum coher…
Protecting coherence in Optimal Control Theory: State dependent constraint approach
最优控制理论的任务是在希尔伯特空间的一个子空间中获得一个主要目标，同时避免希尔伯特空间的其他子空间。主要目标可以是国家到国家的过渡或单一的转换。引入了一个新的优化泛函，使算法具有单调收敛性。这种方法成为必要的分子系统的过程意味着损失的连贯性，如预解离或电离。在这些子空间中，可控性受到阻碍，甚至完全丧失。避免有损信道是通过函数约束来实现的，该函数约束取决于系统在每个时刻的状态。我们概述了由此产生的新算法，讨论其收敛特性，并证明其功能的例子，一个国家到国家的过渡和一个单一的变换模型的冷Rb 2。
Quantum coherence and control in one- and two-photon optical systems
我们从理论和实验两方面研究了单光子和双光子光学系统中的相干性。在第一种情况下，我们开发的密度运营商表示一个单光子状态进行观察（极化）和未观察到的（频率）自由度之间的非耗散耦合。我们表明，实施的“bang-bang”量子控制保护光子偏振信息从某些类型的退相干。在第二种情况下，我们研究了在相似耦合作用下，双光子偏振态的希尔伯特空间中“无消相干”子空间的存在性。密度算子表示的解析和数值求解。注：本手稿摘自作者的本科论文（A.B.达特茅斯学院，2000年6月，由Walter E. Lawrence），在Paul G.奎亚特
Controlling the Dynamical Evolution of Quantum Coherence and Quantum Correlations in $ e^{+}e^{-} \to Λ\barΛ$ Processes at BESIII
本研究针对基本粒子系统维持量子相干的难题，分析BESIII上$e^{+}e^{-} \to Λ\barΛ$过程中量子相干与关联对散射角的依赖，发现经典关联可延缓其衰减，为高能物理与量子信息研究提供新参考。
We propose a scheme to control quantum coherence of a two-component Bose-Einstein condensate (BEC) by a single impurity atom immersed in the BEC. We show that the single impurity atom can act as a single atom valve (SAV) to control quantum coherence of the two-component BEC. It is demonstrated that the SAV can realize the on-demand control over quantum coherence at an arbitrary time. Specially, it is found that the SAV can also control higher-order quantum coherence of two-component BEC. We investigate the long-time evolution of quantum coherence of the two-component BEC. It is indicated that …
Control of quantum coherence of photons exploiting quantum entanglement
提出利用量子纠缠和局域相位操纵技术，在不改变光子强度分布下精确控制光子高阶量子相干性，可扩展至高阶并促进量子传感与成像应用。
Optimal control of population and coherence in three-level $Λ$ systems
最优控制理论的实现，一个有效的人口转移和创建一个最大的三能级系统的一致性被认为是。我们证明了半STIRAP（受激拉曼绝热通道）方案的最大拉曼相干的创建是根据最优控制理论的最优解决方案。我们还提出了一个比较研究的最优控制理论的几个实施方案，适用于完整的人口转移和创造的最大连贯性。分析了共轭梯度法、Zhu-Rabitz法和Krotov法的性能。
Controlling the coherence in a pure dephasing model for an arbitrarily prescribed time span
我们提出了一个开环单一的策略来控制的相干性在一个纯粹的退相模型（相位翻转通道相关），能够恢复，无论规定的时间跨度，在控制过程结束时的初始相干性。该策略的核心思想是使用微调的控制哈密顿量，将量子态引导到不变态的子集，并在必要的时间内保持不变。
Quantum coherence control usually requires extremely low temperature environments. Even for spins in diamond, a remarkable exception, the coherence signal is lost as temperature approaches 700 K. Here we demonstrate quantum coherence control of the electron spins of nitrogen-vacancy centers in nanodiamonds at temperatures near 1000 K. The scheme is based on initialization and readout of the spins at room temperature and control at high temperature, which is enabled by pulse laser heating and rapid diffusion cooling of nanodiamonds on amorphous carbon films. Using high-temperature spin control,…
Symmetry operations and Critical Behaviour in Classical to Quantum Stochastic Processes
本文利用对称操作生成经典马尔可夫链的多种量子扩展，发现不同扩展的弛豫行为差异显著，并揭示相干性度量与弛豫速度关系模糊，且临界指数在短时与长时标度下不同。
Coherence vortices in one spatial dimension
相干涡旋是Glauber的两点量子相干性相位中的螺旋型拓扑缺陷，与系综平均随机量子场不相关的空间点对相关联。相干涡旋可能存在于维数太低而不能支持空间涡旋的系统中。我们展示了这种量子相干相位缺陷的一维模型量子系统的晶格。我们讨论了相干涡旋的物理意义，并提出了如何实现实验。
Spectroscopic experiments have identified long-lived coherences in several light-harvesting systems, suggesting that coherent effects may be relevant to their performance. However, there is limited experimental evidence of coherence enhancing light-harvesting efficiency, largely due to the difficulty of turning coherences on and off to create an experimental control. Here, we show that coherence can indeed enhance light harvesting, and that this effect can be controlled. We construct a model system in which initial coherence can be controlled using the incident light, and which is significantl…
Explaining the observed long coherence effects by 2D photon echo experiments in photosynthetic EET : Two-Component Phonon Spectrum model
本研究提出双组分声子谱（TCPS）随机模型，将声子自由度分为系统组分和随机组分分别处理，成功解释了光合激发能量传输实验中约600飞秒的长相干效应。
We demonstrate time-resolved nonlinear extreme-ultraviolet absorption spectroscopy on multiply charged ions, here applied to the doubly charged neon ion, driven by a phase-locked sequence of two intense free-electron laser pulses. Absorption signatures of resonance lines due to 2$p$--3$d$ bound--bound transitions between the spin-orbit multiplets $^3$P$_{0,1,2}$ and $^3$D$_{1,2,3}$ of the transiently produced doubly charged Ne$^{2+}$ ion are revealed, with time-dependent spectral changes over a time-delay range of $(2.4\pm0.3)\,\text{fs}$. Furthermore, we observe 10-meV-scale spectral shifts o…
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