Brian R. La Cour, Corey I. Ostrove, Michael J. Starkey, Granville E. Ott
We demonstrate that a classical emulation of quantum gate operations, here represented by an actual analog electronic device, can be modeled accurately as a quantum operation in terms of a universal set of Pauli operators. This observation raises the possibility that quantum error correction methods may be applied to classical systems to improve fault tolerance.
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Quantum computation in decoherence-free subspace with superconducting devices
我们提出了一个在无消相干子空间中利用超导器件通过非常规几何操作实现量子计算的方案。利用腔辅助相互作用可以在编码量子比特中实现通用的单量子比特门。一个基于测量的双量子比特受控非门是由辅助超导设备辅助奇偶测量产生的，然后是规定的单量子比特门。对两个并联器件的电流测量可以实现投影测量，相当于对所涉及器件的奇偶测量。
Quantum sensors, such as the Nitrogen Vacancy (NV) color center in diamond, are known for their exquisite sensitivity, but their performance over time are subject to degradation by environmental noise. To improve the long-term robustness of a quantum sensor, here we realize an integrated combinatorial spin sensor in the same micrometer-scale footprint, which exploits two different spin sensitivities to distinct physical quantities to stabilize one spin sensor with local information collected in realtime via the second sensor. We show that we can use the electronic spins of a large ensemble of …
Physical implementation of topologically decoherence-protected superconducting qubits
我们提出了一种方案，物理实现一种拓扑消相干保护量子比特使用超导器件耦合到微波腔模式与非常规的几何操作。它示出的两个所需的相互作用的选择性设备，这是需要实施这样的保护量子位，以及单量子位门，可以通过使用外部磁通量来实现。与在捕获离子系统中实施拓扑保护量子位相比，系统中提出的单个寻址与多设备设置的简单组合呈现出明显的优点。
Quantum spin networks form a generic system to describe a range of quantum devices for quantum information processing and sensing applications. Understanding how to control them is essential to achieve devices with practical functionalities. Energy landscape shaping is a novel control paradigm to achieve selective transfer of excitations in a spin network with surprisingly strong robustness towards uncertainties in the Hamiltonians. Here we study the effect of decoherence, specifically generic pure dephasing, on the robustness of these controllers. Results indicate that while the effectiveness…
Entanglement of coherent states and decoherence
讨论了产生强相干态纠缠叠加的可能性。本文对Howell和Yazell最近提出的一种使两个强相干相干态纠缠的装置[Phys.Rev.A62，012102（2000）]进行了批判性的研究。提出了一种新的改进方案，证明了该方案确实能产生违反贝尔不等式的非经典态。此外，深入分析了损耗和退相干对纠缠度的影响。它揭示了设备对任何干扰的高灵敏度和生成状态的脆弱性。
We apply modern techniques from quantum optics and quantum information science to Bose-Einstein Condensates (BECs) in order to study, for the first time, the quantum decoherence of phonons of isolated BECs. In the last few years, major advances in the manipulation and control of phonons have highlighted their potential as carriers of quantum information in quantum technologies, particularly in quantum processing and quantum communication. Although most of these studies have focused on trapped ion and crystalline systems, another promising system that has remained relatively unexplored is BECs.…
Quantum Superposition of a Mirror and Relative Decoherence (as Spontaneous Superposition Breaking)
Marshall等人的量子叠加实验（迈克耳孙干涉仪的振荡部分）与单光子相互作用的相对退相干解释，这种相对退相干（基于反射镜（测量装置）对光子（量子物体）的自发叠加破缺（有效隐藏））足以模拟真实测量。
A Unified Picture of Decoherence Control
从能量守恒原理和禁戒跃迁的概念出发，从统一的角度讨论了量子器件中减小退相干的各种方法。最小退相干模型、“bang-bang”技术、Zeno效应和无退相干子空间和子系统作为特例进行了研究。
We study quantum decoherence numerically in a system consisting of a relativistic quantum field theory coupled to a measuring device that is itself coupled to an environment. The measuring device and environment are treated as quantum, non-relativistic particles. We solve the Schrödinger equation for the wave function of this tripartite system using exact diagonalization. Although computational limitations on the size of the Hilbert space prevent us from exploring the regime where the device and environment consist of a truly macroscopic number of degrees of freedom, we nevertheless see clear …
Decoherence of surface phonons in a quantum acoustic system
本文通过与超导 transmon 量子比特强耦合的 SAW 谐振器，结合主方程模拟和量子比特辅助光谱，表征表面声子的能量衰减与纯退相位率。
Measurement, Decoherence and Chaos in Quantum Pinball
在"量子弹球“系统中引入测量设备的效果被证明会导致玻姆的量子力学方法中定义的粒子位置的混沌演化。
Analysis of a quantum logic device based on dipole-dipole interactions of optically trapped Rydberg atoms
本文详细分析和设计了一种基于光阱中原子间里德伯态偶极-偶极耦合相互作用的中性原子量子逻辑器件。列举了导致退相干和保真度损失的主要物理机制。我们的研究结果支持在MHz速率下执行单和双量子比特门的可行性，对于每个操作，退相干概率和保真度误差在$10^{-3}$的水平。目前的局限性和可能的方法，以进一步改善设备进行了讨论。
Decoherence in a Pair of Long-Lived Cooper-Pair Boxes
研究了两个Al/AlOx/Al库珀对盒耦合到集总元件超导LC谐振器中量子态的退相干。在25 mK时，第一个量子位的能量弛豫时间T1在4 GHz和8 GHz之间从30 us变化到200 us，并且显示出T1和与微波驱动线的耦合之间的逆相关性。拉姆齐条纹衰减时间T2* 在200-500 ns范围内，而自旋回波包络衰减时间Techo在2.4-3.3 us之间变化，与具有0.2 MHz高频截止的1/f电荷噪声一致。具有类似参数的第二个库珀对盒量子比特显示，在4-7.3 GHz之间T1=4-30 us，并且T1和耦合再次呈负相关。虽然第二个器件的寿命比第一个器件的寿命短，但两个器件对耦合的依赖性表明，耦合的进一步减少应该会导致量子比特性能的改善。
Quantum decoherence plays a pivotal role in the dynamical description of the quantum-to-classical transition and is the main impediment to the realization of devices for quantum information processing. This paper gives an overview of the theory and experimental observation of the decoherence mechanism. We introduce the essential concepts and the mathematical formalism of decoherence, focusing on the picture of the decoherence process as a continuous monitoring of a quantum system by its environment. We review several classes of decoherence models and discuss the description of the decoherence …
By using quantum mechanical effects, quantum computers promise significant speedups in solving problems intractable for conventional computers. However, despite recent progress they remain limited in scaling and availability-making quantum software and hardware development heavily reliant on quantum simulators running on conventional hardware. However, most of those simulators mimic perfect quantum computers and, hence, ignore the fragile nature of quantum mechanical effects which frequently yield to decoherence errors in real quantum devices. Considering those errors during the simulation is …
Decoherence is the fundamental obstacle limiting the performance of quantum information processing devices. The problem of transmitting a quantum state (known or unknown) from one place to another is of great interest in this context. In this work, by following the recent theoretical proposal [Opt. Eng. {\bf 59}, 061625 (2020)] we study an application of quantum state-dependent pre- and post-processing unitary operations for protecting the given (multi-qubit) quantum state against the effect of decoherence acting on all qubits. We observe the increase in the fidelity of the output quantum stat…
The current stage of quantum computing technology, called noisy intermediate-scale quantum (NISQ) technology, is characterized by large errors that prohibit it from being used for real applications. In these devices, decoherence, one of the main sources of error, is generally modeled by Markovian master equations such as the Lindblad master equation. In this work, the decoherence phenomena are addressed from the perspective of the steepest-entropy-ascent quantum thermodynamics (SEAQT) framework in which the noise is in part seen as internal to the system. The framework is as well used to descr…
The dynamics of a quantum anharmonic oscillator whose position is monitored by a Bose-Einstein condensate (BEC) trapped in a symmetric double well potential is studied. The (non-exponential) decoherence induced on the oscillator by the measuring device is analysed. A detailed quasiclassical and quantum analysis is presented. In the first case, for an arbitrary initial coherent state, two different decoherence regimes are observed: An initial Gaussian decay followed by a power law decay for longer times. The characteristic time scales of both regimes are reported. Analytical approximated expres…
Using continuous measurement to protect a universal set of quantum gates within a perturbed decoherence-free subspace
我们考虑一组通用的量子门编码在一个受扰的消相干的四个物理量子比特的子空间。使用二阶微扰理论和测量装置建模的无限组的谐振子，简单地耦合到系统中，我们表明，连续观察的偶联剂诱导抑制的退相干由于杂散扰动。因此，我们提出了保护甚至创建一个消相干子空间来处理量子信息的想法。
Experimental protection of quantum gates against decoherence and control errors
实现量子器件的最大挑战之一是要求执行精确的量子门。与环境相互作用的破坏性影响是精确量子控制必须克服的一些最困难的障碍。在这项工作中，我们实现了一个原理性的实验证明量子门的波动环境中使用动态去耦技术保护。我们证明了在应用量子门的过程中可以降低退相干。即使选通时间超过退相干时间一个数量级，也可以实现高保真度的量子门。
Shift of quantum critical point of discrete time crystal on a noisy quantum simulator
本研究通过噪声量子模拟器探讨了退相干对离散时间晶体临界行为的影响，发现退相干会改变相变边界位置，强调了在近期量子硬件上模拟多体系统时需关注退相干问题。
Measuring the quality factor of a microwave cavity using superconduting qubit devices
提出了一种利用单模微波腔场与超导电荷量子比特相互作用产生两个宏观量子态叠加的方法。这种叠加的退相干可以通过测量腔场的维格纳函数或电荷量子比特态来确定。然后由叠加态的退相干可以推知腔的品质因数Q。即使当$Q$值相对较低并且量子位与腔场之间的相互作用较弱时，所提出的方法在当前技术内也是实验上可实现的。
Recent experiments show the existence of collective decoherence in quantum systems. We study the possibility of quantum computation in decoherence free subspace which is robust against such kind of decoherence processes. This passive protection protocol can be especially advantageous for continuous quantum computation such as quantum annealers. As an example we propose to use decoherence protected adiabatic quantum computation for the Grover search problem. Our proposal contains only two-body interactions, making it feasible in near-term quantum devices.
Channel nonlocality under decoherence
本文量化双向量子信道的非局域性，识别抵抗退相位噪声的成分，并证明其在量子协议及噪声通信中的关键作用，同时揭示退相干下量子模拟随机过程的通信优势。
Realization of a Decoherence-free, Optimally Distinguishable Mesoscopic Quantum Superposition
我们报道了利用高增益的量子注入光参量放大实现了M=12光子的纠缠量子叠加。发现该系统对退相干具有很高的弹性，在常温下表现出直接可访问的介观干涉效应。利用现代层析成像方法，证明了动态“封闭系统”整个介观输出态的不可分离性和量子叠加性。该装置实现了埃尔温·薛定谔在1935年的典范“猫”的辩护中所设想的条件，这是量子力学的一个基本里程碑。
Heralding an Arbitrary Decoherence-Free Qubit State
我们提出了一种光学器件，它能够预示各种DFS状态，防止集体噪声。具体地说，它可以准备跨越DFS quutrit的所有三个基态以及任意编码的DFS量子比特状态。我们还讨论了一种干涉技术，用于确定与任意编码相关的振幅。预示的状态可能会发现使用在相干光学系统中表现出集体相关。
Decoherence and the retrieval of lost information
我们发现，与一般的假设相反，对开放量子系统环境的测量可以{ \em降低}其退相干率。我们通过研究一个间接量子比特测量的例子来证明这一点，其中关于其状态的信息隐藏在环境中。该信息由与环境耦合的远程设备提取。我们还表明，该设备产生的退相干的减少，伴随着减少的量子比特附近的环境噪声。这些结果在大尺度上的量子干涉的解释。
Coulomb blockade in microscopic material defects as a source of decoherence and noise in solid-state quantum circuits
研究固态量子器件中退相干问题，通过扫描门显微镜发现源于金属颗粒库仑阻塞和微波驱动电荷隧穿的新退相干机制，其与TLS缺陷不同且常被传统技术误判，消除金属颗粒可抑制此机制提升器件性能。
We experimentally emulate, in a controlled fashion, the non-Markovian dynamics of a pure dephasing spin-boson model at zero temperature. Specifically, we use a randomized set of external radio-frequency fields to engineer a desired noise power-spectrum to effectively realize a non-Markovian environment for a single NMR qubit. The information backflow, characteristic to the non-Markovianity, is captured in the nonmonotonicity of the decoherence function and von Neumann entropy of the system. Using such emulated non-Markovian environments, we experimentally study the efficiency of the Carr-Purce…
The performance of modern quantum devices in communication, metrology or microscopy relies on the quantum-classical interaction which is generally described by the theory of decoherence. Despite the high relevance for long coherence times in quantum electronics, decoherence mechanisms mediated by the Coulomb force are not well understood yet and several competing theoretical models exist. Here, we present an experimental study of the Coulomb-induced decoherence of free electrons in a superposition state in a biprism electron interferometer close to a semiconducting and metallic surface. The de…
Entanglement transformation at absorbing and amplifying four-port devices
介质四端口器件在光量子信息处理中起着重要的作用。由于因果关系的原因，介电常数是频率的复函数，因此介电常数是噪声量子信道的典型示例，其不能保持量子相干性。为了研究量子退相干效应，我们从给定复介电常数的任意Kramers-Kronig介质中的量子化电磁场出发，构造了输出量子态到输入量子态的变换，而不对频率施加限制。我们将该方法应用于量子通信中的一些典型例子。特别是，我们表明，对于纠缠量子比特的贝尔基状态$|Ψ^\pm>$是更强大的抗退相干比状态$|Φ^\pm>$。
Quantum Decoherence of Single-Photon Counters
量子系统与环境的相互作用导致了所谓的量子退相干。除了它的基本意义之外，在各种情况下对这种动力学的理解和可能的控制是掌握量子信息处理的关键因素。在这里，我们报告的定量探测什么可以被称为量子退相干的检测器，一个过程让人想起的退相干的量子态的存在下，耦合与水库。我们演示了如何在噪声环境的影响下，两个单光子计数器的量子特性消失。因此，我们在实验上见证了测量设备的全量子操作到“半经典状态”之间的过渡，由正维格纳函数描述。这两种制度之间的确切边界是明确确定和测量实验。
Efficient Chromatic-Number-Based Multi-Qubit Decoherence and Crosstalk Suppression
针对量子计算中的退相干与串扰问题，提出基于色数和阿达玛矩阵的动态解耦方法CHaDD，实现脉冲调度深度随色数线性扩展，显著优于现有方案，并在IBM QPUs上验证其优势。
"Device-independent" not only represents a relaxation of the security assumptions about the internal working of the quantum devices, but also can enhance the security of the quantum communication. In the paper, we put forward the first device-independent quantum secure direct communication (DI-QSDC) protocol, where no assumptions are made about the way the devices work or on what quantum system they operate. We show that in the absence of noise, the DI-QSDC protocol is absolutely secure and there is no limitation for the communication distance. However, under practical noisy quantum channel co…
Decoherence of transported spin in multichannel spin-orbit coupled spintronic devices: Scattering approach to spin density matrix from the ballistic to the localized regime
通过将自旋电子器件的检测引线中的电流看作是对应于混合量子态的流动自旋的集合，其中每个自旋本身通常由在传输期间产生的不适当的混合来描述，其中由于自旋-轨道（SO）相互作用或不均匀的磁场，我们引入了与这种电流相关的自旋密度算符，该自旋密度算符用器件的自旋分辨朗道传输矩阵表示。这种形式主义，它提供了完整的描述连接到外部探针的开放的有限尺寸系统中的耦合自旋-电荷量子输运，是用来了解如何最初注入纯自旋态，包括完全自旋极化电流，演变成混合的对应于部分极化电流。我们分析了降低自旋相干性的特定路线（由电流自旋密度矩阵的非对角元素的衰减表示），这是由于Rashba和/或DresselhausSO耦合的相互作用以及：（i）弹道半导体纳米线中的边界或引线界面处的散射;或（ii）在弱和强局域无序纳米线中的静态杂质的自旋无关散射。在多通道量子输运过程中自旋退相干的物理解释，即自旋纠缠到由一个以上的开放轨道传导通道组成的有效零温度"环境“，提供了对自旋电子学的一些关键挑战的深入了解：控制输运自旋的退相干和部分相干自旋态的出现，基于实际半导体结构中SO相互作用的电自旋操纵方案。
In this paper we present a novel approach to emulating a universal quantum computer with a classical system, one that uses a signal of bounded duration and amplitude to represent an arbitrary quantum state. The signal may be of any modality (e.g., acoustic, electromagnetic, etc), but we focus our discussion here on electronic signals. Unitary gate operations are performed using analog electronic circuit devices, such as four-quadrant multipliers, operational amplifiers, and analog filters, although non-unitary operations may be performed as well. In this manner, the Hilbert space structure of …
Decoherence Bounds on Quantum Computation with Trapped Ions
使用简单的物理参数，我们调查的能力的量子计算机的基础上冷囚禁离子。从自发衰变，激光相位相干性，离子加热和其他来源的错误施加在这样的设备上的限制，我们得到的激光相互作用的数量和可以使用的离子的数量之间的界限。确定了可以使用各种离子分解的最大数量。
We experimentally perform the simulation of open quantum dynamics in single-qudit systems. Using a spatial light modulator as a dissipative optical device, we implement dissipative-dynamical maps onto qudits encoded in the transverse momentum of spontaneous parametric down-converted photon pairs. We show a well-controlled technique to prepare entangled qudits states as well as to implement dissipative local measurements; the latter realize two specific dynamics: dephasing and amplitude damping. Our work represents a new analogy-dynamical experiment for simulating an open quantum system.
Ultradecoherence model of the measurement process
本文提出测量过程的超退相干模型，将测量装置建模为具有最快退相干动力学的开放系统，并证明可从底层参数推导点击率，适用于理想测量装置和光子探测器。
Resurrection of Schrodinger Cat
量子退相干是利用工程量子动力学的潜力来革新高精度测量、灵敏检测或信息处理的主要障碍。实验证明了系统的量子态在被不可控的自然退相干破坏后可以恢复。物理体系是液晶中单标记~（13）C-苯的七个偶极耦合核自旋的团簇。13 C自旋扮演着测量质子“猫”态的设备的角色，猫态是六个向上自旋（活跃）和六个向下自旋（死亡）的状态叠加。存储在13 C自旋中的状态信息用于将质子子系统带入活跃状态，而退相干产生的过量熵则转移到“测量设备”13 C自旋。
The decoherence of quantum states defines the transition between the quantum world and classical physics. Decoherence or, analogously, quantum mechanical collapse events pose fundamental questions regarding the interpretation of quantum mechanics and are technologically relevant because they limit the coherent information processing performed by quantum computers. We have discovered that the transition regime enables a novel type of matter transport. Applying this discovery, we present nanoscale devices in which decoherence, modeled by random quantum jumps, produces fundamentally novel phenome…
Detecting Classically Undetectable Particles through Quantum Decoherence
一些假设的粒子被认为基本上是不可探测的，因为它们太轻，移动速度太慢，无法将可观的能量或动量传递给构成探测器的正常物质。我建议直接探测这种微弱的粒子，比如亚MeV的暗物质，甚至引力子，通过它们在物质干涉仪等量子设备上独特的可区分的退相干效应。更一般地说，退相干可以揭示对正常物质具有任意小的经典影响的现象，为追求宏观叠加提供新的动力。
Transport phenomena on a quantum scale appear in a variety of systems, ranging from photosynthetic complexes to engineered quantum devices. It has been predicted that the efficiency of quantum transport can be enhanced through dynamic interaction between the system and a noisy environment. We report the first experimental demonstration of such environment-assisted quantum transport, using an engineered network of laser-written waveguides, with relative energies and inter-waveguide couplings tailored to yield the desired Hamiltonian. Controllable decoherence is simulated via broadening the band…
Optomechanical superpositions via nested interferometry
我们提出了一个在光机系统中实现宏观量子叠加的方案，通过使用单光子后选择和嵌套干涉仪检测它们。这种方法缓解了许多与先前用于测量宏观叠加的光学方案相关的挑战，并且仅需要设备处于弱耦合状态。它只需要对当前可实现的设备参数进行小幅改进，并且允许在不受系统光学衰减时间约束的时间尺度上观察退相干。观察新的退相干机制的前景进行了讨论。
Electron spin qubits are a promising platform for quantum computation. Environmental noise impedes coherent operations by limiting the qubit relaxation ($T_1$) and dephasing ($T_ϕ$) times. There are multiple sources of such noise, which makes it important to devise experimental techniques that can detect the spatial locations of these sources and determine the type of source. In this paper, we propose that anisotropy in $T_1$ and $T_ϕ$ with respect to the direction of the applied magnetic field can reveal much about these aspects of the noise. We investigate the anisotropy patterns of charge n…
Decoherence in Solid State Qubits
固态量子比特与环境自由度的相互作用强烈地影响量子比特的动力学，并导致退相干。在固态量子比特的量子信息处理中，退相干严重限制了器件的性能。因此，有必要充分了解导致退相干的机制。在这篇综述中，我们讨论了退相干如何影响两个最成功的实现固态量子比特，即自旋量子比特和超导量子比特。在前者中，量子比特被编码在电子的自旋1/2中，并且它通过将电子自旋限制在半导体量子点中来实现。超导器件在低温下表现出量子行为，量子比特被编码在超导电路的两个最低能级中。量子点中的电子自旋具有两个主要的退相干通道，由于自旋-轨道相互作用的存在，（马尔可夫）声子辅助的弛豫通道，以及由通过超精细相互作用与电子自旋相互作用的量子点中的核的自旋构成的（非马尔可夫）自旋浴。在超导量子比特中，退相干是由于控制参数（例如偏置电流、施加的通量和偏置电压）的波动以及耗散电路元件中的损耗而发生的。
The advent of quantum devices, which exploit the two essential elements of quantum physics, coherence and entanglement, has sparked renewed interest in the control of open quantum systems. Successful implementations face the challenge to preserve the relevant nonclassical features at the level of device operation. A major obstacle is decoherence which is caused by interaction with the environment. Optimal control theory is a tool that can be used to identify control strategies in the presence of decoherence. We review here recent advances in optimal control methodology that allow for tackling …
Decoherence is a fundamental obstacle to the implementation of large-scale and low-noise quantum information processing devices. In this work, we suggest an approach for suppressing errors by employing pre-processing and post-processing unitary operations, which precede and follow the action of a decoherence channel. In contrast to quantum error correction and measurement-based methods, the suggested approach relies on specifically designed unitary operators for a particular state without the need in ancillary qubits or post-selection procedures. We consider the case of decoherence channels ac…
Suppressing non-Markovian noises by coupling the qubit to a chaotic device
为了抑制耦合到非马尔可夫噪声中的固态量子比特的退相干，我们提出了一种将量子比特与混沌器件耦合的策略，该策略利用量子比特在高频域的宽功率分布来冻结噪声，就像动态解耦控制（DDC）方法一样。与DDC相比，该混沌装置在低频场的驱动下也能产生高频分量，并且不需要优化控制场来产生复杂的控制脉冲。作为超导电路的应用，我们发现，在宽频域中的各种噪声，包括低频$1/f$，高频欧姆，亚欧姆和超欧姆噪声，可以有效地抑制耦合到Duffing振荡器的量子比特，量子比特的退相干率有效地降低了约100倍的幅度。
Direct Detection of Classically Undetectable Dark Matter through Quantum Decoherence
虽然已经收集了各种关于暗物质性质的间接证据，但尽管付出了大量努力，它的直接探测还是避开了实验搜索。如果暗物质的质量低于1 MeV，则传统的探测方法基本上无法察觉，因为在碰撞期间可以忽略不计的能量被转移到原子核。在这里，我建议直接检测暗物质通过量子退相干，而不是它的经典效应，如反冲或电离。我表明，量子空间叠加是敏感的低质量的暗物质，是无法进入的经典技术。这为大质量物质干涉测量提供了新的独立动力，特别是在星载平台上。当太阳穿过银河系时，我们所经历的明显的暗物质风确保了干涉仪和相关设备是定向探测器，因此能够提供明确无误的证据，证明退相干起源于银河系。
Computational advantages gained by quantum algorithms rely largely on the coherence of quantum devices and are generally compromised by decoherence. As an exception, we present a quantum algorithm for graph isomorphism testing whose performance is optimal when operating in the partially coherent regime, as opposed to the extremes of fully coherent or classical regimes. The algorithm builds on continuous-time quantum stochastic walks (QSWs) on graphs and the algorithmic performance is quantified by the distinguishing power (DIP) between non-isomorphic graphs. The QSW explores the entire graph a…
The Schrodinger and Heisenberg pictures are equivalent formulations of quantum mechanics. Here we use the Schrodinger picture to calculate the decoherence that occurs when an optical Schrodinger cat state is passed through a beam splitter. We find that an exponentially large amount of decoherence can occur even when there is a negligible change in the quadrature operator x(t) in the Heisenberg picture. Similar results have been observed in the decoherence produced by an optical amplifier, and we suggest that the usual quadrature operators in the Heisenberg picture do not provide a complete des…
Quantum Computers, Factoring, and Decoherence
在量子计算机中，输入的任何叠加都统一地演化为相应的输出叠加。最近已经证明，这种计算机可以显着加快寻找大数因子的任务-一个具有重大实际意义的问题，因为它的密码应用。最快的经典算法所需的近似指数（$\sim \exp L^{1/3}$，对于具有$L$数字的数字）时间，量子算法给出了$L$（$\sim L^2$）中时间多项式的因子。这种巨大的加速在原则上是可能的，因为量子计算可以同时遵循与不同经典输入相对应的所有路径，作为备选方案之间相干量子干涉的结果获得解决方案。因此，量子计算机是复杂的干涉装置，并且其量子态在操作过程中保持相干是必不可少的。在这份报告中，我们研究了退相干对量子因子分解算法的影响，并根据每个操作步骤所遭受的退相干，建立了一个"量子因子分解“$L$的上限。
Physics-based mathematical models for quantum devices via experimental system identification
我们考虑量子器件的本征控制系统识别的任务。考虑子空间约束的实验确定问题，并提出了控制二能级系统的完全哈密顿识别和消相干特性的简单的一般策略。
Petz recovery maps of single-qubit decoherence channels in an ion trap quantum processor
本文提出在离子阱中实现单量子比特退相干通道的精确状态特定 Petz 恢复映射，设计了仅需少量辅助比特和 CNOT 门的电路，并在现实噪声下模拟验证了其性能与先验知识要求。
Beyond The Fermi's Golden Rule: Discrete-Time Decoherence Of Quantum Mesoscopic Devices Due To Bandlimited Quantum Noise
本文利用量子噪声的带限特性，基于Kotelnikov采样定理将其建模为离散时间过程，从而为介观量子器件在费米黄金规则之外的实时耗散动力学提供了微观推导的碰撞模型和带限输入-输出形式。
Decoherence of a matter-wave interferometer due to dipole-dipole interactions
本文研究偶极-偶极相互作用引起的纳米颗粒物质波干涉仪退相干，从QED推导出散射模型并给出短长波长极限下的退相干率公式，应用于QGEM协议评估相干时间及缓解需求。
Decoherence Limits the Cost to Simulate an Anharmonic Oscillator
本研究探讨退相干如何通过恢复半经典截断维格纳近似，提高克尔非简谐振子量子动力学的模拟效率，并揭示其非凸噪声特性。
TRAM: A Transverse Relaxation Time-Aware Qubit Mapping Algorithm for NISQ Devices
TRAM是一种考虑横向弛豫时间的量子比特映射算法，通过优化相干性来提升NISQ设备的量子电路执行保真度和效率。
Combined encoding and decoupling solution to problems of decoherence and design in solid-state quantum computing
对于可扩展的量子计算设备的提议不仅由于与其环境的相互作用而遭受退相干，而且还遭受严重的工程约束。在这里，我们介绍了这些主要问题的实际解决方案，特别是解决固态提案。首先通过将一个逻辑量子比特编码成两个量子比特来减少去相干，然后通过一组有效的去耦合脉冲序列来完全消除去相干。相同的编码消除了对单量子位操作的需要，这构成了困难的设计约束。我们进一步展示了如何占主导地位的退相干过程可以确定经验，以优化去耦脉冲。
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