Vittorio Giovannetti, Seth Lloyd, Lorenzo Maccone, Peter W. Shor
We calculate the entanglement assisted capacity of a multimode bosonic channel with loss. As long as the efficiency of the channel is above 50%, the superdense coding effect can be used to transmit more bits than those that can be stored in the message sent down the channel. Bounds for the other capacities of the multimode channel are also provided.
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Theory of Multimode Squeezed Light Generation in Lossy Media
本文提出统一理论框架描述有损介质中多模压缩光，推导高斯态二阶关联主方程，证明传统模式分解无法提取最大压缩，并构造了使压缩最大化的新宽带基及算法。
We study the communication capacities of bosonic broadband channels in the presence of different sources of noise. In particular we analyze lossy channels in presence of white noise and thermal bath. In this context, we provide a numerical solution for the entanglement assisted capacity and upper and lower bounds for the classical and quantum capacities.
Numerical Framework for Modeling Quantum Electromagnetic Systems Involving Finite-Sized Lossy Dielectric Objects in Free Space
该研究提出并开发了一种基于计算电磁方法（有限元法）的数值框架，用于修正的朗之万噪声形式，以模拟自由空间中有损介电物体附近的量子电磁系统，并首次数值验证了自发辐射率传统表达式（格林函数虚部）的恢复，适用于多能级原子在等离子体结构或超表面附近的动力学估计。
Neural Network Assisted Fermionic Compression Encoding: A Lossy-QSCI Framework for Resource-Efficient Ground-State Simulations
提出Lossy-QSCI框架，结合Chemical-RLE压缩量子态与NN-FED解码，降低量子比特需求并克服测量挑战，实现资源高效的基态模拟。
In this work we analyse the structure of highly-entangled multimode squeezed states, such as those generated by broadband pulses undergoing type-II parametric down-conversion (PDC). Such down-conversion has previously been touted as a natural and efficient means of cluster-state generation, and therefore a viable future pathway to quantum computation. We first detail how broadband PDC processes lead directly to a series of orthogonal supermodes that are linear combinations of the original frequency modes. We then calculate the total squeezing of the multimode entangled states when they are ass…
Synchronized Quantum Devices in Lossy Channels
针对卫星到地面有损信道中的量子设备同步问题，提出偏振辅助协议，实验证明可扩展同步范围并增加40%距离，蒙特卡洛模拟验证其广泛适用性。
If a quantum channel is commutable with a certain set of operators, a Choi state of the channel becomes a sufficient resource for any entanglement generation achieved by a single use of the channel with the help of local operation and classical communications (LOCC). This property, called the teleportation stretchable, could be useful to determine an upper bound of a fundamental rate-loss trade-off for optical quantum key distribution. Unfortunately, the known formulation of the teleportation-stretching expansion for lossy Gaussian channels is based on an additional assumption of the Choi stat…
AI-assisted hyper-dimensional broadband quantum memory with efficiency above 90% in warm atoms
针对高维量子存储效率不足的问题，本文利用改进DE算法优化信号—控制波形匹配，在热原子中实现22维OAM/SAM光子宽带存储，效率达80%–92%、保真度达92%–99%。
Bipartite entanglement extracted from multimode squeezed light generated in lossy waveguides
研究通过II型参数下转换在损耗波导中生成多模式光，提取双模式纠缠态，并通过压缩量量化纠缠，构建最优测量基。
The major resolution-limiting factor in cryoelectron microscopy of unstained biological specimens is radiation damage by the very electrons that are used to probe the specimen structure. To address this problem, an electron microscopy scheme that employs quantum entanglement to enable phase measurement precision beyond the standard quantum limit has recently been proposed {[}Phys. Rev. A \textbf{85}, 043810{]}. Here we identify and examine in detail measurement errors that will arise in the scheme. An emphasis is given to considerations concerning inelastic scattering events because in general…
Long distance quantum illumination and ranging using polarization entangled photon pairs in a lossy environment
本研究利用偏振纠缠光子对在损耗环境中实现远距离量子照明与测距，展示了纠缠光子的鲁棒性和长距离传播的可行性。
Sensing and measurement tasks in severely adverse conditions such as loss, noise and dephasing can be improved by illumination with quantum states of light. Previous results have shown a modest reduction in the number of measurements necessary to achieve a given precision. Here, we compare three illumination strategies for estimating the relative phase in a noisy, lossy interferometer. When including a common phase fluctuation in the noise processes, we show that using an entangled probe achieves an advantage in parameter estimation precision that scales with the number of entangled modes. Thi…
Machine-learning-assisted material and geometry characterization from Casimir force measurement
本文利用机器学习方法从Casimir力测量中推断纳米薄膜的厚度和介电常数，展示了量子真空波动作为宽带电磁源在材料表征中的应用潜力。
Criteria for optimal entanglement-assisted long baseline telescopy
针对纠缠辅助长基线望远镜最优资源与判据不明确的问题，本文提出整合量子计量工具与超选择规则的框架，基于SSR约束下的QFI量化估计问题，推导基本极限并提出超先前方法的新协议，为实用方案提供启发。
Entanglement has been known to boost target detection, despite it being destroyed by lossy-noisy propagation. Recently, [Phys. Rev. Lett. 128, 010501 (2022)] proposed a quantum pulse-compression radar to extend entanglement's benefit to target range estimation. In a radar application, many other aspects of the target are of interest, including angle, velocity and cross section. In this study, we propose a dual-receiver radar scheme that employs a high time-bandwidth product microwave pulse entangled with a pre-shared reference signal available at the receiver, to investigate the direction of a…
Optimal entanglement-assisted electromagnetic sensing and communication in the presence of noise
针对现有宽带TMSV态接收机无法发挥全部量子优势的问题，提出含相关-位移转换器等模块的新接收机架构，可在有损有噪的传感与通信场景中实现最优量子性能。
We study quantum channels that vary on time in a deterministic way, that is, they change in an independent but not identical way from one to another use. We derive coding theorems for the classical entanglement assisted and unassisted capacities. We then specialize the theory to lossy bosonic quantum channels and show the existence of contrasting examples where capacities can or cannot be drawn from the limiting behavior of the lossy parameter.
We determine conditions for the presence of stochastic resonance in a lossy bosonic channel with a nonlinear, threshold decoding. The stochastic resonance effect occurs if and only if the detection threshold is outside of a "forbidden interval". We show that it takes place in different settings: when transmitting classical messages through a lossy bosonic channel, when transmitting over an entanglement-assisted lossy bosonic channel, and when discriminating channels with different loss parameters. Moreover, we consider a setting in which stochastic resonance occurs in the transmission of a qub…
Exceptional-point-assisted entanglement, squeezing, and reset in a chain of three superconducting resonators
本研究利用三超导谐振器链中的例外点工程，实现快速量子态合成，包括压缩与纠缠的准稳态传输及系统低失真重置，为光子网络的量子态调控提供了新方案。
Entanglement offers substantial advantages in quantum information processing, but loss and noise hinder its applications in practical scenarios. Although it has been well known for decades that the classical communication capacity over lossy and noisy bosonic channels can be significantly enhanced by entanglement, no practical encoding and decoding schemes are available to realize any entanglement-enabled advantage. Here, we report structured encoding and decoding schemes for such an entanglement-assisted communication scenario. Specifically, we show that phase encoding on the entangled two-mo…
In the presence of arbitrary three-dimensional linear media with material loss and amplification, we present an electromagnetic field quantization scheme for quasinormal modes (QNMs), extending previous work for lossy media [Franke et al., Phys. Rev. Lett. 122, 213901 (2019)]. Applying a symmetrization transformation, we show two fundamentally different ways for constructing a QNM photon Fock space, including (i) where there is a separate operator basis for both gain and loss, and (ii) where the loss and gain degrees of freedom are combined into a single basis. These QNM operator bases are sub…
Dissipative Channels Determine Open Electromagnetic Quantization
提出一种开放电磁系统的量子化方案，通过麦克斯韦算子的耗散几何识别储层，将涨落通道分为介质辅助和边界辅助两类，并导出格林函数输入输出关系，应用于有损结构和光子集成电路。
Entanglement underpins a variety of quantum-enhanced communication, sensing, and computing capabilities. Entanglement-assisted communication (EACOMM) leverages entanglement pre-shared by communication parties to boost the rate of classical information transmission. Pioneering theory works showed that EACOMM can enable a communication rate well beyond the ultimate classical capacity of optical communications, but an experimental demonstration of any EACOMM advantage remains elusive. Here, we report the implementation of EACOMM surpassing the classical capacity over lossy and noisy bosonic chann…
Transceiver designs to attain the entanglement assisted communications capacity
针对高噪声低亮度信道，提出两种量子收发机设计，利用预共享纠缠、二进制相位调制和非高斯联合检测，实现纠缠辅助容量相对霍列沃容量的对数增益，并改进接收机以达理论容量。
Quantum communications promises reliable transmission of quantum information, efficient distribution of entanglement and generation of completely secure keys. For all these tasks, we need to determine the optimal point-to-point rates that are achievable by two remote parties at the ends of a quantum channel, without restrictions on their local operations and classical communication, which can be unlimited and two-way. These two-way assisted capacities represent the ultimate rates that are reachable without quantum repeaters. By constructing an upperbound based on the relative entropy of entang…
We consider quantum and private communications assisted by repeaters, from the basic scenario of a single repeater chain to the general case of an arbitrarily-complex quantum network, where systems may be routed through single or multiple paths. In this context, we investigate the ultimate rates at which two end-parties may transmit quantum information, distribute entanglement, or generate secret keys. These end-to-end capacities are defined by optimizing over the most general adaptive protocols that are allowed by quantum mechanics. Combining techniques from quantum information and classical …
Secret-sharing building blocks based on quantum broadcast communication are studied. The confidential capacity region of the pure-loss bosonic broadcast channel is determined, both with and without key assistance, and an achievable region is established for the lossy bosonic broadcast channel. If the main receiver has a transmissivity of η<1/2, then confidentiality solely relies on the key-assisted encryption of the one-time pad. We also address conference key agreement for the distillation of two keys, a public key and a secret key. A regularized formula is derived for the key-agreement capac…
Joint Communication and Sensing with Bipartite Entanglement over Bosonic Channels
研究利用双粒子纠缠在光子信道中实现通信与传感的联合优化，通过量子优势提升通信速率与传感精度。
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