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Quantum-enhanced measurements use quantum mechanical effects in order to enhance the sensitivity of the measurement of classical quantities, such as the length of an optical cavity. The major goal is to beat the standard quantum limit…

Quantum Physics · Physics 2011-03-10 Daniel Braun , John Martin

Quantum sensing has seen rapid progress from laboratory research to real-world applications. Solid-state spin systems, particularly nitrogen-vacancy (NV) centers in diamond, are attractive for their ability to operate at room temperature…

Quantum Physics · Physics 2025-07-22 Jonathan Kenny , Feifei Zhou , Ruihua He , Fedor Jelezko , Teck Seng Koh , Weibo Gao

The standard quantum limit (SQL), also known as the shot-noise limit, defines how quantum fluctuations of light constrain measurement precision. In a benchmark experiment using the Mach-Zehnder interferometer (MZI), where a coherent state…

State-of-the-art sensors of force, motion and magnetic fields have reached the sensitivity where the quantum noise of the meter is significant or even dominant. In particular, the sensitivity of the best optomechanical devices has reached…

Quantum Physics · Physics 2021-05-05 Farid Ya. Khalili , Emil Zeuthen

Quantum entanglement can provide enhanced precision beyond standard quantum limit (SQL), the highest precision achievable with classical means. It remains challenging, however, to observe large enhancement limited by the experimental…

Quantum Gases · Physics 2022-12-20 Tian-Wei Mao , Qi Liu , Xin-Wei Li , Jia-Hao Cao , Feng Chen , Wen-Xin Xu , Meng Khoon Tey , Yi-Xiao Huang , Li You

The performance of solid-state quantum sensors based on electronic spin defects is often limited by the presence of environmental spin impurities that cause decoherence. A promising approach to improve these quantum sensors is to convert…

Quantum Physics · Physics 2019-10-30 Alexandre Cooper , Won Kyu Calvin Sun , Jean-Christophe Jaskula , Paola Cappellaro

Precision metrology underpins scientific and technological advancements. Quantum metrology offers a pathway to surpass classical sensing limits by leveraging quantum states and measurement strategies. However, measuring multiple…

Quantum metrology makes use of coherent superpositions to detect weak signals. While in principle the sensitivity can be improved by increasing the density of sensing particles, in practice this improvement is severely hindered by…

Building robust instruments capable of making interferometric measurements with precision beyond the standard quantum limit remains an important goal in many metrology laboratories. We describe here the basic concepts underlying spin…

Quantum Physics · Physics 2015-06-03 Hermann Uys , Michael J. Biercuk , Joe Britton , John J. Bollinger

The concepts of separability, entanglement, spin-squeezing and Heisenberg limit are central in the theory of quantum enhanced metrology. In the current literature, these are well established only in the case of linear interferometers…

Quantum Physics · Physics 2013-05-29 P. Hyllus , L. Pezzé , A. Smerzi

Entangled quantum probes can achieve Heisenberg-limited measurement precision, but this advantage is typically destroyed by noise. We address this issue by introducing a framework that we call encoded quantum signal processing, which…

Quantum Physics · Physics 2026-03-25 Carlos Ortiz Marrero , Rui Jie Tang , Nathan Wiebe

Entanglement, a key feature of quantum mechanics, is a resource that allows the improvement of precision measurements beyond the conventional bound reachable by classical means. This is known as the standard quantum limit, already defining…

Other Condensed Matter · Physics 2008-12-09 J. Esteve , C. Gross , A. Weller , S. Giovanazzi , M. K. Oberthaler

The quantum metrological performance of spin coherent states superposition is considered, and conditions for measurements with the Heisenberg-limit (HL) precision are identified. It is demonstrated that the choice of the…

Quantum Physics · Physics 2021-10-26 Yusef Maleki

The ability to determine precisely the separation of two frequencies is fundamental to spectroscopy, yet the resolution limit poses a critical challenge: distinguishing two incoherent signals becomes impossible when their frequencies are…

Quantum Physics · Physics 2025-12-29 Qingyun Cao , Genko T. Genov , Yaoming Chu , Jianming Cai , Yu Liu , Alex Retzker , Fedor Jelezko

Quantum metrology aims to enhance measurement precision beyond the standard quantum limit (SQL), the benchmark set by classical resources, enabling advances in sensing, imaging, and fundamental physics. A critical milestone beyond the SQL…

Quantum Physics · Physics 2025-08-19 Kimin Park , Tanjung Krisnanda , Yvonne Gao , Radim Filip

Displacement sensing is a fundamental task in metrology. However, the development of quantum-enhanced sensors that fully utilize the available degrees of freedom in many-body quantum systems remains an outstanding challenge. We propose…

A recent proposal for testing Lorentz symmetry violation (LSV) presents a formulation where the effect of violation is described as a local interaction [R. Shaniv, et al, Phys. Rev. Lett. 120, 103202 (2018)]. An entangled ion pair in a…

Quantum Physics · Physics 2019-05-01 Lei Li , Xinwei Li , Baocheng Zhang , Li You

Quantum metrology studies the use of entanglement and other quantum resources to improve precision measurement. An interferometer using N independent particles to measure a parameter X can achieve at best the "standard quantum limit" (SQL)…

Quantum Physics · Physics 2012-03-06 M. Napolitano , M. Koschorreck , B. Dubost , N. Behbood , R. J. Sewell , M. W. Mitchell

Quantum effects in metrology can in principle enhance measurement precision from the so-called standard quantum limit to the Heisenberg Limit. Further advancements in quantum metrology largely rely on innovative metrology protocols that can…

Quantum Physics · Physics 2025-06-16 Zhixing Zou , Jiangbin Gong , Weitao Chen

The use of special quantum states to achieve sensitivities below the limits established by classically behaving states has enjoyed immense success since its inception. In bosonic interferometers, squeezed states, number states and cat…