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The quantum noise of light fundamentally limits optical phase sensors. A semiclassical picture attributes this noise to the random arrival time of photons from a coherent light source such as a laser. An engineered source of squeezed states…

We present an innovative optical imaging system for measuring parameters of a small particle such as a macromolecule or nanoparticle at the quantum limit of sensitivity. In comparison to the conventional confocal interferometric scattering…

Quantum Physics · Physics 2025-07-14 Fabian Müller , Emre Köse , Alfred J. Meixner , Erik Schäffer , Daniel Braun

Quantum illumination is a technique for detecting the presence of a target in a noisy environment by means of a quantum probe. We prove that the two-mode squeezed vacuum state is the optimal probe for quantum illumination in the scenario of…

Quantum Physics · Physics 2018-07-11 Giacomo De Palma , Johannes Borregaard

The simultaneous two-parameter estimation problem in single squeezed-light Mach-Zehnder interferometer with double-port homodyne detection is investigated in this work. The analytical form of the two-parameter quantum Cramer-Bao bound…

Quantum Physics · Physics 2024-02-19 Li-li Hou , Jian-Dong Zhang , Kai-Min Zheng , Shuai Wang

Quantum noise will be the dominant noise source for the advanced laser interferometric gravitational wave detectors currently under construction. Squeezing-enhanced laser interferometers have been recently demonstrated as a viable technique…

Instrumentation and Detectors · Physics 2015-06-23 Katherine L Dooley , Emil Schreiber , Henning Vahlbruch , Christoph Affeldt , Jonathan R Leong , Holger Wittel , Hartmut Grote

This paper explores the sensitivity gains afforded by spin-squeezed states in atom interferometry, in particular using Bragg diffraction. We introduce a generalised input-output formalism that accurately describes realistic, non-unitary…

Quantum Physics · Physics 2026-05-29 Julian Günther , Jan-Niclas Kirsten-Siemß , Naceur Gaaloul , Klemens Hammerer

Every measurement of the population in an uncorrelated ensemble of two-level systems is limited by what is known as the quantum projection noise limit. Here, we present quantum projection noise limited performance of a Ramsey type…

Quantum Physics · Physics 2010-04-29 D. Döring , G. McDonald , J. E. Debs , C. Figl , P. A. Altin , H. -A. Bachor , N. P. Robins , J. D. Close

We investigate an optimal distance of two components in an entangled coherent state for quantum phase estimation in lossy interferometry. The optimal distance is obtained by an economical point, representing the quantum Fisher information…

Quantum Physics · Physics 2020-01-28 Su-Yong Lee , Yong Sup Ihn , Zaeill Kim

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…

Quantum Physics · Physics 2022-02-16 Alex O. C. Davis , Giacomo Sorelli , Valerian Thiel , Brian J. Smith

The Cram\'er-Rao bound captures completely the performance of single-parameter quantum sensors. On the other hand, its extension to multiple parameters demands more caution. Different aspects need to be captured at once, including,…

Quantum Physics · Physics 2026-01-14 Jayanth Jayakumar , Marco Barbieri , Magdalena Stobińska

Quantum-correlated interferometer is a newly emerging tool in quantum technology that offers classical-limit-breaking phase sensitivity. But to date, there exists a configurational bottleneck for its practicability due to the low…

Atomic Physics · Physics 2025-01-10 Wei Du , Shuhe Wu , Dong Zhang , Jun Chen , Yiquan Yang , Peiyu Yang , Jinxian Guo , Guzhi Bao , Weiping Zhang

The problem of long-distance teleportation of single-atom qubits via a common photonic channel is examined within the framework of a Mach-Zender optical interferometer. As expected, when a coherent state is used as input, a high-finesse…

Quantum Physics · Physics 2007-05-23 Y. P. Huang , M. G. Moore

We derive a general expression of the quantum Fisher information for a Mach-Zehnder interferometer, with the port inputs of an \emph{arbitrary} pure state and a squeezed thermal state. We find that the standard quantum limit can be beaten,…

Quantum Physics · Physics 2014-05-20 Qing-Shou Tan , Jie-Qiao Liao , Xiaoguang Wang , Franco Nori

In this paper, we derive a general expression of the quantum Fisher information of an SU(1,1) interferometer with an arbitrary state and a Fock state as inputs by the phase-averaging method. Our results show that the same quantum Fisher…

Quantum Physics · Physics 2021-05-11 Shuai Wang , Jian-Dong Zhang , Xue-Xiang Xu

A setup for discriminating between arbitrary two coherent states of a single light mode with the highest success rate allowed by quantum mechanics is presented. Its application to time-multiplexed quantum key distribution is discussed.

Quantum Physics · Physics 2009-10-31 Konrad Banaszek

Quantum interferometers offer phase measurement capabilities that surpass the standard quantum limit (SQL), with phase sensitivity and quantum enhancement factor serving as key performance metrics. However, practical implementations face…

Quantum Physics · Physics 2026-01-27 Jie Zhao , Zeliang Wu , Haoran Liu , Yueya Liu , Xin Chen , Xinyun Liang , Wenfeng Huang , Chun-Hua Yuan , L. Q. Chen

Quantum-enhanced metrology can be achieved by entangling a probe with an auxiliary system, passing the probe through an interferometer, and subsequently making measurements on both the probe and auxiliary system. Conceptually, this…

Quantum Physics · Physics 2015-09-22 Simon A. Haine , Stuart S. Szigeti

Quantum optical sensors are ubiquitous in various fields of research, from biological or medical sensors to large-scale experiments searching for dark matter or gravitational waves. Gravitational-wave detectors have been very successful in…

Quantum Physics · Physics 2024-01-11 Mikhail Korobko , Jan Südbeck , Sebastian Steinlechner , Roman Schnabel

Differential interferometry (DI) with two coupled sensors is a most powerful approach for precision measurements in presence of strong phase noise. However DI has been studied and implemented only with classical resources. Here we…

Quantum Physics · Physics 2015-06-22 M. Landini , M. Fattori , L. Pezze , A. Smerzi

Atom interferometers are reaching sensitivities fundamentally constrained by quantum fluctuations. A main challenge is to integrate entanglement into quantum sensing protocols to enhance precision while ensuring robustness against noise and…