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Genuine multimode entanglement in continuous variable systems can be quantified by exploring the geometry of the state-space, namely via the generalized geometric measure (GGM) which is defined as the shortest distance of a given multimode…

Quantum Physics · Physics 2020-07-22 Saptarshi Roy , Tamoghna Das , Aditi Sen De

In this paper we explore the possibility of performing Heisenberg limited quantum metrology of a phase, without any prior, by employing only maximally entangled states. Starting from the estimator introduced by Higgins et al. in New J.…

Quantum Physics · Physics 2020-10-27 Federico Belliardo , Vittorio Giovannetti

Multi-photon entangled states play a crucial role in quantum information applications such as secure quantum communication, scalable computation, and high-precision quantum metrology. Quantum memory for entangled states is a key component…

Quantum Physics · Physics 2018-12-19 Wei Zhang , Ming-Xin Dong , Dong-Sheng Ding , Shuai Shi , Kai-Wang , Zhi-Yuan Zhou , Guang-Can Guo , Bao-Sen Shi

Entanglement is a fundamental feature of quantum mechanics and holds great promise for enhancing metrology and communications. Much of the focus of quantum metrology so far has been on generating highly entangled quantum states that offer…

The examination of entanglement across various degrees of freedom has been pivotal in augmenting our understanding of fundamental physics, extending to high dimensional quantum states, and promising the scalability of quantum technologies.…

Quantum Physics · Physics 2024-04-26 Dongjin Lee , Woncheol Shin , Sebae Park , Junyeop Kim , Heedeuk Shin

We study the performance of efficient quantum state tomography methods based on neural network quantum states using measured data from a two-photon experiment. Machine learning inspired variational methods provide a promising route towards…

For a fixed average energy, the simultaneous estimation of multiple phases can provide a better total precision than estimating them individually. We show this for a multimode interferometer with a phase in each mode, using Gaussian inputs…

Quantum Physics · Physics 2016-11-03 Christos N. Gagatsos , Dominic Branford , Animesh Datta

The power of quantum sensing rests on its ultimate precision limit, quantified by the quantum Cramer-Rao bound (QCRB), which can surpass classical bounds. In multi-parameter estimation, the QCRB is not always saturated as the quantum nature…

Quantum Physics · Physics 2024-05-24 Changhao Li , Mo Chen , Paola Cappellaro

We consider the problem of a state determination for a two-level quantum system which can be in one of two nonorthogonal mixed states. It is proved that for the two independent identical systems the optimal combined measurement (which…

Quantum Physics · Physics 2007-05-23 A. E. Allahverdyan , D. B. Saakian

We first review and critically examine some basic concepts and ambiguities related to quantum mechanics and quantum measurement to understand the success and shortcomings of current theories. We also touch on ideas regarding expression of…

Quantum Physics · Physics 2009-11-05 Fariel Shafee

It has been discussed recently how quantum illumination can be used to increase the accuracy of the value range-delay measurement \cite{Zhuang Shapiro 2022} in the domain of SNR compatible with current radar systems. However, the advantage…

Quantum Physics · Physics 2023-05-10 Ricardo Gallego Torromé

Quantum phase classification is a fundamental problem in quantum many-body physics, traditionally approached using order parameters or quantum machine learning techniques such as quantum convolutional neural networks (QCNNs). However, these…

Quantum Physics · Physics 2026-02-05 Akira Tanji , Hiroshi Yano , Naoki Yamamoto

Optimal phase estimation of a phase-squeezed quantum state of light has been recently shown to beat the coherent-state limit. Here, the estimation is made robust to uncertainties in underlying parameters using a robust fixed-interval…

Quantum Physics · Physics 2015-09-14 Shibdas Roy , Ian R. Petersen , Elanor H. Huntington

As neural networks are known to efficiently represent classes of tensor-network states as well as volume-law-entangled states, identifying which properties determine the representational capabilities of neural quantum states (NQS) remains…

Nuclear Theory · Physics 2026-03-31 James W. T. Keeble , Alessandro Lovato , Caroline E. P. Robin

Quantum states of light, such as squeezed states or entangled states, can be used to make measurements (metrology), produce images, and sense objects with a precision that far exceeds what is possible classically, and also exceeds what was…

Quantum Physics · Physics 2009-04-02 Jonathan P. Dowling

Interaction with environment may lead to the transition of quantum system from pure state to the mixed one. In this case, the problem of definition of entanglement may arise. In particular, quantitative measure of entanglement concurrence…

Quantum Physics · Physics 2008-09-16 Levan Chotorlishvili

It is a specific type of quantum correlated state that achieves optimal precision in parameterestimation under unitary encoding. We consider the potential experimental limitation on probe entanglement, and find a relation between achievable…

Quantum Physics · Physics 2026-01-06 Debarupa Saha , Ujjwal Sen

We find the optimal measurement for distinguishing between symmetric multi-mode phase-randomized coherent states. A motivation for this is that phase-randomized coherent states can be used for quantum communication, including quantum…

Quantum Physics · Physics 2024-10-16 Ioannis Petrongonas , Erika Andersson

The estimation of multiple parameters in quantum metrology is important for a vast array of applications in quantum information processing. However, the unattainability of fundamental precision bounds for incompatible observables has…

Quantum Physics · Physics 2021-02-17 Jasminder S. Sidhu , Yingkai Ouyang , Earl T. Campbell , Pieter Kok

Quantum states are represented by positive semidefinite Hermitian operators with unit trace, known as density matrices. An important subset of quantum states is that of separable states, the complement of which is the subset of…

Mathematical Physics · Physics 2020-12-04 Grigoriy Blekherman , H. M. Bharath
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