对于有效的线性光量子计算，单光子源和探测器必须有多好？

Round robin differential phase shift quantum key distribution with yes-no detectors only

In the original round-robin differential-phase-shift (RRDPS) quantum key distribution and its improved method, the photon-number-resolving detectors are must for the security. We present a RRDPS protocol with yes-no detectors only. We get the upper bounds of mutual information of Alice and Eve, and Bob and Eve, and the formula of key rate. Our main idea is to divide all counts into two classes, the counts due to the odd number photons of incident detectors and the counts due to the even number photons of incident detectors. The fact that the bit-flip error rate of the later class is certainly …

光统计的自洽表征

Self-consistent characterization of light statistics

我们证明了一个自洽的光场的光子数统计特性的可能性，通过使用光电发射探测器与内部增益简单地赋予线性输入/输出响应。该方法可以应用于微观和介观光子数制度。探测器必须在线性范围内工作，而不需要光子计数能力。

Quantum detector tomography of a 2x2 multi-pixel array of superconducting nanowire single photon detectors

We demonstrate quantum detector tomography of a commercial 2x2 array of superconducting nanowire single photon detectors. We show that detector-specific figures of merit including efficiency, dark-count and cross-talk probabilities can be directly extracted, without recourse to the underlying detector physics. These figures of merit are directly identified from just four elements of the reconstructed positive operator valued measure (POVM) of the device. We show that the values for efficiency and dark-count probability extracted by detector tomography show excellent agreement with independent …

一种超低噪声负反馈雪崩二极管通信波长自激单光子探测器

An Ultra-Low Noise Telecom Wavelength Free Running Single Photon Detector Using Negative Feedback Avalanche Diode

在1550 nm波长范围内实现真正的自由运行单光子探测器，同时具有高探测效率（DE），低暗噪声和良好的时间分辨率，这是具有挑战性的。我们报告了一种新的读出系统的信号从负反馈雪崩二极管（NFAD），它允许这些设备在193 K的温度下，并在非常低的暗计数（~100 CPS），良好的时间抖动（~30 ps），良好的DE（~10%）的结果有用的操作。利用弱相干光脉冲（WCP）产生的光子和自发参量下转换（SPDC）产生的光子对，用时间相关方法对两个NFAD进行了表征。这两种类型的光子源的推断探测器效率彼此一致。器件的最佳噪声等效功率估计为8.1 × 10^（-18）W Hz^（-1/2），比典型InP/InGaAs SPAD在自激模式下的噪声等效功率高10倍以上。后脉冲的概率被发现是小于0.1%每纳秒在优化的工作点。此外，我们研究了使用这些检测器的基于纠缠的量子密钥分发（QKD）的性能，并开发了一个模型的量子误码率（QBER），其中包括后脉冲系数。我们通过实验验证了使用这些NFAD在400 km的电信光纤上实现QKD是可行的。我们的NFAD光子探测器系统非常简单，非常适合需要超低噪声和自由运行操作的单光子应用，并且可以容忍一些后脉冲。

引力辐射探测干涉仪拓扑的量子极限

Quantum Limits of Interferometer Topologies for Gravitational Radiation Detection

为了扩展引力波探测器的天体物理范围，已经提出了几种干涉仪拓扑结构，以规避未来探测器的热力学和量子力学限制。在这项工作中，我们做了一个系统的比较，其中考虑到他们的敏感性和复杂性。我们通过引入一个成本函数来优化它们的灵敏度，该成本函数试图最大化当前检测器灵敏度的宽带改进。我们发现，频率相关的挤压光注入与百米规模的滤波腔产生了良好的宽带灵敏度，具有低复杂性，对光损耗和良好的鲁棒性。该研究为今后提高引力波探测器性能的近期实验研究提供了指导。

由哪个路径检测器引起的失相

Dephasing due to Which Path Detector

我们研究了哪一个路径探测器引起的电子退相，从而验证了玻尔的费米子互补原理。我们采用了双光路干涉仪与两个狭缝，其中一个狭缝被替换为一个相干的量子点（QD）。一个短的一维通道，在量子点接触（QPC）的形式，在接近的QD，作为一个路径检测器。我们发现，通过改变QPC检测器的属性，我们会影响干扰的可见性，从而诱导退相。我们开发了一个简单的模型来解释由于附近的检测器的失相，并找到与实验很好的协议。

Photon Counting Distribution for Arrays of Single-Photon Detectors

We derive a computationally efficient expression of the photon counting distribution for a uniformly illuminated array of single photon detectors. The expression takes the number of single detectors, their quantum efficiency, and their dark-count rate into account. Using this distribution we compute the error of the array detector by comparing the output to that of a ideal detector. We conclude from the error analysis that the quantum efficiency must be very high in order for the detector to resolve a hand-full of photons with high probability. Furthermore, we conclude that in the worst-case s…

用明亮的光控制主动猝灭的单光子探测器

Controlling an actively-quenched single photon detector with bright light

我们使用明亮的光控制主动猝灭雪崩单光子探测器。主动猝灭检测器通常用于可见光和近红外范围内的量子密钥分发（QKD）。这项研究表明，这些检测器是可控的相同的攻击用于黑客被动淬火和门控检测器。这证明了我们的攻击的通用性和它的可能适用性，eavsdropping的全部密钥的QKD系统使用雪崩光电二极管（APD）。此外，我们测试的商业探测器模型（珀金埃尔默SPCM-AQR）表现出两个新的致盲机制，除了先前观察到的热致盲的APD，即：偏置电压控制电路的故障，和过载的DC/DC转换器偏置APD。在一个检测器模型中发现的这两个新的技术漏洞表明，这个问题必须通过将通常不完美的检测器纳入QKD的安全性证明来解决。

NbN纳米线超导单光子探测器中热点相互作用长度的研究

Probing the Hotspot Interaction Length in NbN Nanowire Superconducting Single-Photon Detectors

我们测量的最大距离，在这两个吸收的光子可以联合触发检测事件在NbN纳米线超导单光子探测器（SSPD）微桥通过比较单光子和双光子效率的不同的总长度的桥梁，从0到400 nm。我们发现长度为$23 \pm 2$ nm。这个值是在良好的协议与准粒子云的大小在检测事件的时间。

Quantum Travel Time and Tunnel Ionization Times of Atoms

Time it takes to travel from one position to another, devoid of any quantum mechanical description, has been modeled variously, especially for quantum tunneling. The model time, if universally valid, must be subluminal, must hold everywhere (inside and outside the tunneling region), must comprise interference effects, and must have a sensible classical limit. Here we show that the quantum travel time, hypothesized to emerge with the state vector, is a function of the probability density and probability current such that all the criteria above are fulfilled. We compute it inside and outside a r…

Measurements in QFT: Weakly coupled local particle detectors and entanglement harvesting

We present a comparison of the AQFT-based Fewster-Verch framework with the Unruh-DeWitt particle detector models commonly employed in relativistic quantum information and QFT in curved space. We use this comparison to respond to a recent paper [arXiv:2103.13400] in which it was argued that the Reeh-Schlieder theorem prevents weakly coupled local particle detectors from harvesting vacuum entanglement from a quantum field. Their claim can be traced back to the mixedness that a local particle detector cannot escape from because of the entanglement that it must have with the quantum fields outside…