Universal continuous-variable quantum computation: Requirement of optical nonlinearity for photon counting

Parity-Time Symmetry-Enhanced Simultaneous Magnon and Photon Blockade in Cavity Magnonic System

The main challenge in the recent demonstration of conventional magnon blockade is to increase the nonlinearity of the system especially in comparison with the dissipation channels. One can consider the Kerr nonlinearity through which magnon blockade in a cavity magnonic system is possible provided that the Kerr nonlinearity is much stronger than the cavity and magnonic mode dissipation rates. In the present contribution, we consider a PT-symmetric cavity magnonic system and study the effect of PT-symmetric phase on the magnon statistics and hence magnon blockade. We show that the PT-symmetric …

Divide-and-Conquer: An integrated photon-counting scheme

The key requirement for harnessing the quantum properties of light is the capability to detect and count individual photons. Of particular interest are photon-number-resolving detectors, which allow one to determine whether a state of light is classical or genuinely quantum. Existing schemes for addressing this challenge rely on a proportional conversion of photons to electrons. As such, they are capable of correctly characterizing small photon fluxes, yet are limited by uncertainties in the conversion rate. In this work, we employ a divide-and-conquer approach to overcome these limitations by…

Minimum requirements for feedback enhanced force sensing

The problem of estimating an unknown force driving a linear oscillator is revisited. When using linear measurement, feedback is often cited as a mechanism to enhance bandwidth or sensitivity. We show that as long as the oscillator dynamics are known, there exists a real-time estimation strategy that reproduces the same measurement record as any arbitrary feedback protocol. Consequently some form of nonlinearity is required to gain any advantage beyond estimation alone. This result holds true in both quantum and classical systems, with non-stationary forces and feedback, and in the general case…

通过单光子 $\chi^{(2)}$ 非线性实现实验性纠缠交换

Experimental entanglement swapping through single-photon $χ^{(2)}$ nonlinearity

本研究通过单光子χ(2)非线性波导中的和频产生实现纠缠交换，利用高信噪比宣告器和GHz超快光源，测得保真度下界0.770(76)，超越经典极限，推动长距离量子通信与光子计算发展。

Quantum metrology of two-photon absorption

Two-photon absorption (TPA) is of fundamental importance in super-resolution imaging and spectroscopy. Its nonlinear character allows for the prospect of using quantum resources, such as entanglement, to improve measurement precision or to gain new information on, e.g., ultrafast molecular dynamics. Here, we establish the metrological properties of nonclassical squeezed light sources for precision measurements of TPA cross sections. We find that there is no fundamental limit for the precision achievable with squeezed states in the limit of very small cross sections. Considering the most releva…

Franson-type experiment realizes two-qubit quantum logic gate

Quantum computers promise great improvements in solving problems such as factoring large integers, simulating quantum systems, and database searching. Using a photon as a quantum bit (qubit) is one of the most promising ways to realize a universal quantum computer because the coherent superposition state of a photon is very robust against various sources of decoherence. However, it is too difficult to realize two-qubit (photon) gates because it requires huge nonlinearity between photons. Here we show the realization of a controlled-NOT (CNOT) gate, the most important and elemental two-qubit ga…

多模式高斯态上通过光子计数测量生成非经典光的 heralding 概率优化

Heralding probability optimization for nonclassical light generated by photon counting measurements on multimode Gaussian states

本文研究了基于高斯态和光子数测量的条件量子态制备方案，通过求解多项式方程优化 heralding 概率，提升量子态制备效率，并展示了该方法在单模和双模态态生成中的应用。

How the Result of Counting One Photon Can Turn Out to Be a Value of 8

In 1988, Aharonov, Albert, and Vaidman introduced a new paradigm of quantum measurement in a paper which had the unwieldy but provocative title "How the result of a measurement of a component of the spin of a spin-1=2 particle can turn out to be 100." This paradigm, so-called "weak measurement," has since been the subject of widespread theoretical and experimental attention, both for the perspective it offers on quantum reality and for possible applications to precision measurement. Yet almost all of the weak-measurement experiments carried out so far could be alternatively understood in terms…

Generation of mechanical interference fringes by multi-photon counting

Exploring the quantum behaviour of macroscopic objects provides an intriguing avenue to study the foundations of physics and to develop a suite of quantum-enhanced technologies. One prominent path of study is provided by quantum optomechanics which utilizes the tools of quantum optics to control the motion of macroscopic mechanical resonators. Despite excellent recent progress, the preparation of mechanical quantum superposition states remains outstanding due to weak coupling and thermal decoherence. Here we present a novel optomechanical scheme that significantly relaxes these requirements al…

量子照明中的不完美光子探测

Imperfect photon detection in quantum illumination

研究量子照明中微波域单光子计数方案在现实探测参数下的性能，发现考虑双混频器输出及相关光子计数（CPC）时，两输出对光子数分辨的要求高度不对称。

适用于混合量子光子学的超亮、高可扩展性压缩光源

An ultra-bright, highly-scalable, squeezed light source for hybrid quantum photonics

本文开发了适配混合量子光子学的超亮高可扩展KTP波导压缩光源，其具备高光子数、模式特性优异等优势，还建立了光子计数表征该光源的理论框架。

基于量子忆阻器的实验神经形态计算

Experimental neuromorphic computing based on quantum memristor

针对量子平台实现神经网络非线性行为的挑战，提出基于光子量子忆阻器的神经形态架构，通过忆阻反馈回路增强非线性，在四个任务上验证了其性能及作为复杂网络构建模块的潜力。

Electrical control of nonlinear quantum optics in a nano-photonic waveguide

Local control of the generation and interaction of indistinguishable single photons is a key requirement for photonic quantum networks. Waveguide-based architectures, in which embedded quantum emitters act as both highly coherent single photon sources and as nonlinear elements to mediate photon-photon interactions, offer a scalable route to such networks. However, local electrical control of a quantum optical nonlinearity has yet to be demonstrated in a waveguide geometry. Here, we demonstrate local electrical tuning and switching of single photon generation and nonlinear interaction by embedd…

费米子计数诱导的广义芝诺效应与纠缠动力学

Generalized Zeno effect and entanglement dynamics induced by fermion counting

本文研究自由费米子在粒子计数测量下的纠缠动力学，结合量子轨迹模拟与复本 Keldysh 场论，揭示其与局域占据测量共享广义芝诺效应及有限共形临界区间。