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Articoli di riviste sul tema "Quantum optics Measurement"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 31 gennaio 2023

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1

Walls, DF. "Quantum Measurements in Atom Optics". Australian Journal of Physics 49, n. 4 (1996): 715. http://dx.doi.org/10.1071/ph960715.

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We review recent progress in atom optics. We describe new quantum measurements based on the entanglement of quantum states of a light field with atomic external degrees of freedom. Examples include the quantum non-demolition measurement of the photon number in a cavity and the measurement of atomic position.

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2

Hradil, Z. "Phase measurement in quantum optics". Quantum Optics: Journal of the European Optical Society Part B 4, n. 2 (aprile 1992): 93–108. http://dx.doi.org/10.1088/0954-8998/4/2/004.

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3

Xavier, Jolly, Deshui Yu, Callum Jones, Ekaterina Zossimova e Frank Vollmer. "Quantum nanophotonic and nanoplasmonic sensing: towards quantum optical bioscience laboratories on chip". Nanophotonics 10, n. 5 (1 marzo 2021): 1387–435. http://dx.doi.org/10.1515/nanoph-2020-0593.

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Abstract Quantum-enhanced sensing and metrology pave the way for promising routes to fulfil the present day fundamental and technological demands for integrated chips which surpass the classical functional and measurement limits. The most precise measurements of optical properties such as phase or intensity require quantum optical measurement schemes. These non-classical measurements exploit phenomena such as entanglement and squeezing of optical probe states. They are also subject to lower detection limits as compared to classical photodetection schemes. Biosensing with non-classical light sources of entangled photons or squeezed light holds the key for realizing quantum optical bioscience laboratories which could be integrated on chip. Single-molecule sensing with such non-classical sources of light would be a forerunner to attaining the smallest uncertainty and the highest information per photon number. This demands an integrated non-classical sensing approach which would combine the subtle non-deterministic measurement techniques of quantum optics with the device-level integration capabilities attained through nanophotonics as well as nanoplasmonics. In this back drop, we review the underlining principles in quantum sensing, the quantum optical probes and protocols as well as state-of-the-art building blocks in quantum optical sensing. We further explore the recent developments in quantum photonic/plasmonic sensing and imaging together with the potential of combining them with burgeoning field of coupled cavity integrated optoplasmonic biosensing platforms.

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4

Walls, DF, MJ Collett, EP Storey e SM Tan. "Quantum Measurements in Atomic Optics". Australian Journal of Physics 46, n. 1 (1993): 61. http://dx.doi.org/10.1071/ph930061.

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We consider atoms traversing a cavity filled with an optical field. When the atoms are well detuned from the optical resonance the output momentum distribution of the atoms is found to be a sensitive probe of the photon statistics of the light field. Near resonance spontaneous emission smears the diffractive peaks. We obtain a good fit to the experimental data of Gould et at. (1991). As the atoms pass through the optical field they impart a position-dependent phase shift to the field. By making a quadrature phase measurement on the optical field a position measurement of the atom is achieved. We show that it is possible to prepare the atom in a 'contractive state' which beats the standard quantum limit for position measurements.

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5

Chabaud, Ulysse, Damian Markham e Adel Sohbi. "Quantum machine learning with adaptive linear optics". Quantum 5 (5 luglio 2021): 496. http://dx.doi.org/10.22331/q-2021-07-05-496.

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We study supervised learning algorithms in which a quantum device is used to perform a computational subroutine – either for prediction via probability estimation, or to compute a kernel via estimation of quantum states overlap. We design implementations of these quantum subroutines using Boson Sampling architectures in linear optics, supplemented by adaptive measurements. We then challenge these quantum algorithms by deriving classical simulation algorithms for the tasks of output probability estimation and overlap estimation. We obtain different classical simulability regimes for these two computational tasks in terms of the number of adaptive measurements and input photons. In both cases, our results set explicit limits to the range of parameters for which a quantum advantage can be envisaged with adaptive linear optics compared to classical machine learning algorithms: we show that the number of input photons and the number of adaptive measurements cannot be simultaneously small compared to the number of modes. Interestingly, our analysis leaves open the possibility of a near-term quantum advantage with a single adaptive measurement.

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6

Molotkov, S. N. "Homodyne detection in quantum optics: deterministic extractors and quantum random number generators on ‘vacuum fluctuations’". Laser Physics 32, n. 5 (7 aprile 2022): 055202. http://dx.doi.org/10.1088/1555-6611/ac5ccc.

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Abstract Quantum random number generators with a continuous variable are considered based on a primary randomness of the outcomes of homodyne measurements of a coherent state. A deterministic method of extraction of truly random 0 and 1 from the primary sequence of measurements of the quadrature of the field in homodyne detection is considered. The method, in the case of independence of successive measurement outcomes, in the asymptotic limit of long sequences, allows us to extract with a polynomial complexity all the true randomness contained in the primary sequence. The method does not require knowledge of the probability distribution function of the primary random sequence, and also does not require additional randomness in the extraction of random 0 and 1. The approach with deterministic randomness extractors, unlike other methods, contains fewer assumptions and conditions that need to be satisfied in the experimental implementation of such generators, and is significantly more effective and simple in experimental implementation. The fundamental limitations dictated by nature for achieving statistical independence of successive measurement outcomes are also considered. The statistical independence of the measurement outcomes is the equivalent of true randomness, in the sense that is possible in the case of the independence of the measurement outcomes, provably, with deterministic extractor, to extract a ‘truly random sequence of 0 and 1’. It is shown that in the asymptotic limit it is possible to extract all the true randomness contained in the outcomes of physical measurements.

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7

Krotkov, Robert. "Quantum Optics, Experimental Gravitation, and Measurement Theory". American Journal of Physics 53, n. 8 (agosto 1985): 795–96. http://dx.doi.org/10.1119/1.14327.

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8

KOASHI, Masato. "Recent Progress in Quantum Optics. Quantum Cryptography and Measurement of Quantum States." Review of Laser Engineering 28, n. 10 (2000): 677–81. http://dx.doi.org/10.2184/lsj.28.677.

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9

Castro Santis, Ricardo. "Quantum stochastic dynamics in multi-photon optics". Infinite Dimensional Analysis, Quantum Probability and Related Topics 17, n. 01 (marzo 2014): 1450007. http://dx.doi.org/10.1142/s0219025714500076.

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Multi-photon models are theoretically and experimentally important because in them quantum properly phenomena are verified; as well as squeezed light and quantum entanglement also play a relevant role in quantum information and quantum communication (see Refs. 18–20).In this paper we study a generic model of a multi-photon system with an arbitrary number of pumping and subharmonics fields. This model includes measurement on the system, as could be direct or homodyne detection and we demonstrate the existence of dynamics in the context of Continuous Measurement Theory of Open Quantum Systems (see Refs. 1–11) using Quantum Stochastic Differential Equations with unbounded coefficients (see Refs. 10–15).

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10

Chen, Sixin, Taxue Ma, Qian Yu, Pengcheng Chen, Xinzhe Yang, Xuewei Wu, Hai Sang et al. "A perspective on the manipulation of orbital angular momentum states in nonlinear optics". Applied Physics Letters 122, n. 4 (23 gennaio 2023): 040503. http://dx.doi.org/10.1063/5.0135224.

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Orbital angular momentum (OAM) of light has been widely investigated in optical manipulation, optical communications, optical storage, and precision measurement. In recent years, the studies of OAM are expanded to nonlinear and quantum optics, paving a way to high-quality nonlinear imaging, high-capacity quantum communication, and many other promising applications. In this Perspective, we first summarize the fundamental research on OAM in nonlinear optics. Then, we introduce its recent applications in nonlinear imaging (including nonlinear spiral imaging and OAM-multiplexing nonlinear holography) and high-dimensional quantum entanglement. In particular, we highlight the manipulations of OAM through various functional nonlinear photonic crystals. Finally, we discuss the further developments of OAM-based nonlinear and quantum techniques in the near future.

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11

Eriksson, K.-E. "Quantum statistics of quantum measurement". Physica Scripta 36, n. 6 (1 dicembre 1987): 870–79. http://dx.doi.org/10.1088/0031-8949/36/6/002.

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12

Semenov, A. A., e A. B. Klimov. "Dual form of the phase-space classical simulation problem in quantum optics". New Journal of Physics 23, n. 12 (1 dicembre 2021): 123046. http://dx.doi.org/10.1088/1367-2630/ac40cc.

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Abstract In quantum optics, nonclassicality of quantum states is commonly associated with negativities of phase-space quasiprobability distributions. We argue that the impossibility of any classical simulations with phase-space functions is a necessary and sufficient condition of nonclassicality. The problem of such phase-space classical simulations for particular measurement schemes is analysed in the framework of Einstein–Podolsky–Rosen–Bell’s principles of physical reality. The dual form of this problem results in an analogue of Bell inequalities. Their violations imply the impossibility of phase-space classical simulations and, as a consequence, nonclassicality of quantum states. We apply this technique to emblematic optical measurements such as photocounting, including the cases of realistic photon-number resolution and homodyne detection in unbalanced, balanced, and eight-port configurations.

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13

Lee, Seung-Woo, Jaewan Kim e Hyunchul Nha. "Complete Information Balance in Quantum Measurement". Quantum 5 (17 marzo 2021): 414. http://dx.doi.org/10.22331/q-2021-03-17-414.

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Quantum measurement is a basic tool to manifest intrinsic quantum effects from fundamental tests to quantum information applications. While a measurement is typically performed to gain information on a quantum state, its role in quantum technology is indeed manifold. For instance, quantum measurement is a crucial process element in measurement-based quantum computation. It is also used to detect and correct errors thereby protecting quantum information in error-correcting frameworks. It is therefore important to fully characterize the roles of quantum measurement encompassing information gain, state disturbance and reversibility, together with their fundamental relations. Numerous efforts have been made to obtain the trade-off between information gain and state disturbance, which becomes a practical basis for secure information processing. However, a complete information balance is necessary to include the reversibility of quantum measurement, which constitutes an integral part of practical quantum information processing. We here establish all pairs of trade-off relations involving information gain, disturbance, and reversibility, and crucially the one among all of them together. By doing so, we show that the reversibility plays a vital role in completing the information balance. Remarkably, our result can be interpreted as an information-conservation law of quantum measurement in a nontrivial form. We completely identify the conditions for optimal measurements that satisfy the conservation for each tradeoff relation with their potential applications. Our work can provide a useful guideline for designing a quantum measurement in accordance with the aims of quantum information processors.

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14

Semenenko, Henry, Philip Sibson, Andy Hart, Mark G. Thompson, John G. Rarity e Chris Erven. "Chip-based measurement-device-independent quantum key distribution". Optica 7, n. 3 (19 marzo 2020): 238. http://dx.doi.org/10.1364/optica.379679.

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15

Wiseman, H. M. "Quantum trajectories and quantum measurement theory". Quantum and Semiclassical Optics: Journal of the European Optical Society Part B 8, n. 1 (febbraio 1996): 205–22. http://dx.doi.org/10.1088/1355-5111/8/1/015.

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16

Wu, Bujiao, Jinzhao Sun, Qi Huang e Xiao Yuan. "Overlapped grouping measurement: A unified framework for measuring quantum states". Quantum 7 (13 gennaio 2023): 896. http://dx.doi.org/10.22331/q-2023-01-13-896.

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Quantum algorithms designed for realistic quantum many-body systems, such as chemistry and materials, usually require a large number of measurements of the Hamiltonian. Exploiting different ideas, such as importance sampling, observable compatibility, or classical shadows of quantum states, different advanced measurement schemes have been proposed to greatly reduce the large measurement cost. Yet, the underline cost reduction mechanisms seem distinct from each other, and how to systematically find the optimal scheme remains a critical challenge. Here, we address this challenge by proposing a unified framework of quantum measurements, incorporating advanced measurement methods as special cases. Our framework allows us to introduce a general scheme – overlapped grouping measurement, which simultaneously exploits the advantages of most existing methods. An intuitive understanding of the scheme is to partition the measurements into overlapped groups with each one consisting of compatible measurements. We provide explicit grouping strategies and numerically verify its performance for different molecular Hamiltonians with up to 16 qubits. Our numerical result shows significant improvements over existing schemes. Our work paves the way for efficient quantum measurement and fast quantum processing with current and near-term quantum devices.

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17

Napolitano, M., M. Koschorreck, B. Dubost, N. Behbood, R. J. Sewell e M. W. Mitchell. "Quantum Optics and the “Heisenberg Limit” of Measurement". Optics and Photonics News 22, n. 12 (1 dicembre 2011): 40. http://dx.doi.org/10.1364/opn.22.12.000040.

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18

Haus, Herman A. "Quantum noise, quantum measurement, and squeezing". Journal of Optics B: Quantum and Semiclassical Optics 6, n. 8 (28 luglio 2004): S626—S633. http://dx.doi.org/10.1088/1464-4266/6/8/001.

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19

Modak, Niladri, Ankit K. Singh, Shyamal Guchhait, Athira BS, Mandira Pal e Nirmalya Ghosh. "Weak Measurements in Nano-optics". Current Nanomaterials 5, n. 3 (21 dicembre 2020): 191–213. http://dx.doi.org/10.2174/2468187310999200723121713.

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Background: Weak measurement involves weak coupling between the system and the measuring device (pointer) enables large amplification and high precision measurement of small physical parameters. The outcome of this special measurement procedure involving nearly mutually orthogonal pre- and post-selection of states in such weakly interacting systems leads to weak value that can become exceedingly large and lie outside the eigenvalue spectrum of the measured observable. This unprecedented ability of weak value amplification of small physical parameters has been successfully exploited for various metrological applications in the optical domain and beyond. Even though it is a quantum mechanical concept, it can be understood using the classical electromagnetic theory of light and thus can be realized in classical optics. Objective: Here, we briefly review the basic concepts of weak measurement and weak value amplification, provide illustrative examples of its implementation in various optical domains. The applications involve measuring ultra-sensitive beam deflections, high precision measurements of angular rotation, phase shift, temporal shift, frequency shift and so forth, and expand this extraordinary concept in the domain of nano-optics and plasmonics. Methods: In order to perform weak value amplification, we have used Gaussian beam and spectral response as the pointer subsequently. The polarization state associated with the pointer is used as pre and post-selection device. Results: We reveal the weak value amplification of sub-wavelength optical effects namely the Goos-Hänchen shift and the spin hall shift. Further, we demonstrate weak measurements using spectral line shape of resonance as a natural pointer, enabling weak value amplification beyond the conventional limit, demonstrating natural weak value amplification in plasmonic Fano resonances and so forth. The discussed concepts could have useful implications in various nano-optical systems to amplify tiny signals or effects. Conclusion: The emerging prospects of weak value amplification towards the development of novel optical weak measurement devices for metrological applications are extensively discussed.

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20

Schenzle, Axel. "Illusion or reality: The measurement process in quantum optics". Contemporary Physics 37, n. 4 (luglio 1996): 303–20. http://dx.doi.org/10.1080/00107519608222156.

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21

Novo, Leonardo, Juani Bermejo-Vega e Raúl García-Patrón. "Quantum advantage from energy measurements of many-body quantum systems". Quantum 5 (2 giugno 2021): 465. http://dx.doi.org/10.22331/q-2021-06-02-465.

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The problem of sampling outputs of quantum circuits has been proposed as a candidate for demonstrating a quantum computational advantage (sometimes referred to as quantum "supremacy"). In this work, we investigate whether quantum advantage demonstrations can be achieved for more physically-motivated sampling problems, related to measurements of physical observables. We focus on the problem of sampling the outcomes of an energy measurement, performed on a simple-to-prepare product quantum state – a problem we refer to as energy sampling. For different regimes of measurement resolution and measurement errors, we provide complexity theoretic arguments showing that the existence of efficient classical algorithms for energy sampling is unlikely. In particular, we describe a family of Hamiltonians with nearest-neighbour interactions on a 2D lattice that can be efficiently measured with high resolution using a quantum circuit of commuting gates (IQP circuit), whereas an efficient classical simulation of this process should be impossible. In this high resolution regime, which can only be achieved for Hamiltonians that can be exponentially fast-forwarded, it is possible to use current theoretical tools tying quantum advantage statements to a polynomial-hierarchy collapse whereas for lower resolution measurements such arguments fail. Nevertheless, we show that efficient classical algorithms for low-resolution energy sampling can still be ruled out if we assume that quantum computers are strictly more powerful than classical ones. We believe our work brings a new perspective to the problem of demonstrating quantum advantage and leads to interesting new questions in Hamiltonian complexity.

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22

Hutchinson, G. D., e G. J. Milburn. "Nonlinear quantum optical computing via measurement". Journal of Modern Optics 51, n. 8 (maggio 2004): 1211–22. http://dx.doi.org/10.1080/09500340408230417.

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23

Schneider, Jessica, Oliver Glöckl, Gerd Leuchs e Ulrik L. Andersen. "Nonunity gain quantum nondemolition measurements based on measurement and repreparation". Optics Letters 31, n. 17 (9 agosto 2006): 2628. http://dx.doi.org/10.1364/ol.31.002628.

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24

Bulaevskii, L. N., e G. Ortiz. "Indirect quantum measurement of a single quantum spin". Physica E: Low-dimensional Systems and Nanostructures 18, n. 1-3 (maggio 2003): 329–30. http://dx.doi.org/10.1016/s1386-9477(02)01071-8.

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Coutts, Bryan, Mark Girard e John Watrous. "Certifying optimality for convex quantum channel optimization problems". Quantum 5 (1 maggio 2021): 448. http://dx.doi.org/10.22331/q-2021-05-01-448.

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We identify necessary and sufficient conditions for a quantum channel to be optimal for any convex optimization problem in which the optimization is taken over the set of all quantum channels of a fixed size. Optimality conditions for convex optimization problems over the set of all quantum measurements of a given system having a fixed number of measurement outcomes are obtained as a special case. In the case of linear objective functions for measurement optimization problems, our conditions reduce to the well-known Holevo-Yuen-Kennedy-Lax measurement optimality conditions. We illustrate how our conditions can be applied to various state transformation problems having non-linear objective functions based on the fidelity, trace distance, and quantum relative entropy.

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26

Haus, H. A., K. Watanabe e Y. Yamamoto. "Quantum-nondemolition measurement of optical solitons". Journal of the Optical Society of America B 6, n. 6 (1 giugno 1989): 1138. http://dx.doi.org/10.1364/josab.6.001138.

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27

Fidder, Henk, e O. Tapia. "The quantum measurement problem". International Journal of Quantum Chemistry 97, n. 1 (8 settembre 2003): 670–78. http://dx.doi.org/10.1002/qua.10771.

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28

Keller, Matthias, e Günter Mahler. "Stochastic dynamics and quantum measurement". Quantum and Semiclassical Optics: Journal of the European Optical Society Part B 8, n. 1 (febbraio 1996): 223–35. http://dx.doi.org/10.1088/1355-5111/8/1/016.

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29

Allahverdyan, Armen E., Roger Balian e Theo M. Nieuwenhuizen. "Dynamics of a quantum measurement". Physica E: Low-dimensional Systems and Nanostructures 29, n. 1-2 (ottobre 2005): 261–71. http://dx.doi.org/10.1016/j.physe.2005.05.023.

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Masada, Genta, e Akira Furusawa. "On-chip continuous-variable quantum entanglement". Nanophotonics 5, n. 3 (1 settembre 2016): 469–82. http://dx.doi.org/10.1515/nanoph-2015-0142.

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AbstractEntanglement is an essential feature of quantum theory and the core of the majority of quantum information science and technologies. Quantum computing is one of the most important fruits of quantum entanglement and requires not only a bipartite entangled state but also more complicated multipartite entanglement. In previous experimental works to demonstrate various entanglement-based quantum information processing, light has been extensively used. Experiments utilizing such a complicated state need highly complex optical circuits to propagate optical beams and a high level of spatial interference between different light beams to generate quantum entanglement or to efficiently perform balanced homodyne measurement. Current experiments have been performed in conventional free-space optics with large numbers of optical components and a relatively large-sized optical setup. Therefore, they are limited in stability and scalability. Integrated photonics offer new tools and additional capabilities for manipulating light in quantum information technology. Owing to integrated waveguide circuits, it is possible to stabilize and miniaturize complex optical circuits and achieve high interference of light beams. The integrated circuits have been firstly developed for discrete-variable systems and then applied to continuous-variable systems. In this article, we review the currently developed scheme for generation and verification of continuous-variable quantum entanglement such as Einstein-Podolsky-Rosen beams using a photonic chip where waveguide circuits are integrated. This includes balanced homodyne measurement of a squeezed state of light. As a simple example, we also review an experiment for generating discrete-variable quantum entanglement using integrated waveguide circuits.

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Shlosberg, Ariel, Andrew J. Jena, Priyanka Mukhopadhyay, Jan F. Haase, Felix Leditzky e Luca Dellantonio. "Adaptive estimation of quantum observables". Quantum 7 (26 gennaio 2023): 906. http://dx.doi.org/10.22331/q-2023-01-26-906.

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The accurate estimation of quantum observables is a critical task in science. With progress on the hardware, measuring a quantum system will become increasingly demanding, particularly for variational protocols that require extensive sampling. Here, we introduce a measurement scheme that adaptively modifies the estimator based on previously obtained data. Our algorithm, which we call AEQuO, continuously monitors both the estimated average and the associated error of the considered observable, and determines the next measurement step based on this information. We allow both for overlap and non-bitwise commutation relations in the subsets of Pauli operators that are simultaneously probed, thereby maximizing the amount of gathered information. AEQuO comes in two variants: a greedy bucket-filling algorithm with good performance for small problem instances, and a machine learning-based algorithm with more favorable scaling for larger instances. The measurement configuration determined by these subroutines is further post-processed in order to lower the error on the estimator. We test our protocol on chemistry Hamiltonians, for which AEQuO provides error estimates that improve on all state-of-the-art methods based on various grouping techniques or randomized measurements, thus greatly lowering the toll of measurements in current and future quantum applications.

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Cenni, Marina F. B., Ludovico Lami, Antonio Acín e Mohammad Mehboudi. "Thermometry of Gaussian quantum systems using Gaussian measurements". Quantum 6 (23 giugno 2022): 743. http://dx.doi.org/10.22331/q-2022-06-23-743.

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We study the problem of estimating the temperature of Gaussian systems with feasible measurements, namely Gaussian and photo-detection-like measurements. For Gaussian measurements, we develop a general method to identify the optimal measurement numerically, and derive the analytical solutions in some relevant cases. For a class of single-mode states that includes thermal ones, the optimal Gaussian measurement is either Heterodyne or Homodyne, depending on the temperature regime. This is in contrast to the general setting, in which a projective measurement in the eigenbasis of the Hamiltonian is optimal regardless of temperature. In the general multi-mode case, and unlike the general unrestricted scenario where joint measurements are not helpful for thermometry (nor for any parameter estimation task), it is open whether joint Gaussian measurements provide an advantage over local ones. We conjecture that they are not useful for thermal systems, supported by partial analytical and numerical evidence. We further show that Gaussian measurements become optimal in the limit of large temperatures, while {on/off} photo-detection-like measurements do it for when the temperature tends to zero. Our results therefore pave the way for effective thermometry of Gaussian quantum systems using experimentally realizable measurements.

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Barut, A. O., M. Božić, S. Klarsfeld e Z. Marić. "Measurement of time-dependent quantum phases". Physical Review A 47, n. 4 (1 aprile 1993): 2581–91. http://dx.doi.org/10.1103/physreva.47.2581.

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Loveridge, L., e P. Busch. "‘Measurement of quantum mechanical operators’ revisited". European Physical Journal D 62, n. 2 (25 marzo 2011): 297–307. http://dx.doi.org/10.1140/epjd/e2011-10714-3.

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Taylor, Michael A., Jiri Janousek, Vincent Daria, Joachim Knittel, Boris Hage, Hans-A. Bachor e Warwick P. Bowen. "Biological measurement beyond the quantum limit". Nature Photonics 7, n. 3 (3 febbraio 2013): 229–33. http://dx.doi.org/10.1038/nphoton.2012.346.

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Feihu Xu, Marcos Curty, Bing Qi e Hoi-Kwong Lo. "Measurement-Device-Independent Quantum Cryptography". IEEE Journal of Selected Topics in Quantum Electronics 21, n. 3 (maggio 2015): 148–58. http://dx.doi.org/10.1109/jstqe.2014.2381460.

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Milburn, G. J., e S. Basiri-Esfahani. "Quantum optics with one or two photons". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 471, n. 2180 (agosto 2015): 20150208. http://dx.doi.org/10.1098/rspa.2015.0208.

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We discuss the concept of a single-photon state together with how they are generated, measured and interact with linear and nonlinear systems. In particular, we consider how a single-photon state interacts with an opto-mechanical system: an optical cavity with a moving mirror and how such states can be used as a measurement probe for the mechanical degrees of freedom. We conclude with a discussion of how single-photon states are modified in a gravitational field due to the red-shift.

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Wang, Jipeng, Zhenhua Li, Zhongqi Sun, Tianqi Dou, Wenxiu Qu, Fen Zhou, Yanxin Han, Yuqing Huang e Haiqiang Ma. "Loss-tolerant measurement device independent quantum key distribution with reference frame misalignment". Chinese Optics Letters 20, n. 9 (2022): 092701. http://dx.doi.org/10.3788/col202220.092701.

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Miyazaki, Jisho, e Keiji Matsumoto. "Imaginarity-free quantum multiparameter estimation". Quantum 6 (10 marzo 2022): 665. http://dx.doi.org/10.22331/q-2022-03-10-665.

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Multiparameter quantum estimation is made difficult by the following three obstacles. First, incompatibility among different physical quantities poses a limit on the attainable precision. Second, the ultimate precision is not saturated until you discover the optimal measurement. Third, the optimal measurement may generally depend on the target values of parameters, and thus may be impossible to perform for unknown target states. We present a method to circumvent these three obstacles. A class of quantum statistical models, which utilizes antiunitary symmetries or, equivalently, real density matrices, offers compatible multiparameter estimations. The symmetries accompany the target-independent optimal measurements for pure-state models. Based on this finding, we propose methods to implement antiunitary symmetries for quantum metrology schemes. We further introduce a function which measures antiunitary asymmetry of quantum statistical models as a potential tool to characterize quantumness of phase transitions.

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40

Bhaumik, Mani L. "Can Decoherence Solve the Measurement Problem?" Quanta 11, n. 1 (4 dicembre 2022): 115–23. http://dx.doi.org/10.12743/quanta.v11i1.208.

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Abstract (sommario):

The quantum decoherence program has become more attractive in providing an acceptable solution for the long-standing quantum measurement problem. Decoherence by quantum entanglement happens very quickly to entangle the quantum system with the environment including the detector. But in the final stage of measurement, acquiring the unentangled pointer states poses some problems. Recent experimental observations of the effect of the ubiquitous quantum vacuum fluctuations in destroying quantum entanglement appears to provide a solution.Quanta 2022; 11: 115–123.

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41

Morgan, Peter. "Classical states, quantum field measurement". Physica Scripta 94, n. 7 (16 aprile 2019): 075003. http://dx.doi.org/10.1088/1402-4896/ab0c53.

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42

Wang, Kai, James G. Titchener, Sergey S. Kruk, Lei Xu, Hung-Pin Chung, Matthew Parry, Ivan I. Kravchenko et al. "Quantum metasurface for multiphoton interference and state reconstruction". Science 361, n. 6407 (13 settembre 2018): 1104–8. http://dx.doi.org/10.1126/science.aat8196.

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Metasurfaces based on resonant nanophotonic structures have enabled innovative types of flat-optics devices that often outperform the capabilities of bulk components, yet these advances remain largely unexplored for quantum applications. We show that nonclassical multiphoton interferences can be achieved at the subwavelength scale in all-dielectric metasurfaces. We simultaneously image multiple projections of quantum states with a single metasurface, enabling a robust reconstruction of amplitude, phase, coherence, and entanglement of multiphoton polarization-encoded states. One- and two-photon states are reconstructed through nonlocal photon correlation measurements with polarization-insensitive click detectors positioned after the metasurface, and the scalability to higher photon numbers is established theoretically. Our work illustrates the feasibility of ultrathin quantum metadevices for the manipulation and measurement of multiphoton quantum states, with applications in free-space quantum imaging and communications.

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43

Kondo, Ruho, Yuki Sato, Satoshi Koide, Seiji Kajita e Hideki Takamatsu. "Computationally Efficient Quantum Expectation with Extended Bell Measurements". Quantum 6 (13 aprile 2022): 688. http://dx.doi.org/10.22331/q-2022-04-13-688.

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Evaluating an expectation value of an arbitrary observable A∈C2n×2n through naïve Pauli measurements requires a large number of terms to be evaluated. We approach this issue using a method based on Bell measurement, which we refer to as the extended Bell measurement method. This analytical method quickly assembles the 4n matrix elements into at most 2n+1 groups for simultaneous measurements in O(nd) time, where d is the number of non-zero elements of A. The number of groups is particularly small when A is a band matrix. When the bandwidth of A is k=O(nc), the number of groups for simultaneous measurement reduces to O(nc+1). In addition, when non-zero elements densely fill the band, the variance is O((nc+1/2n)tr(A2)), which is small compared with the variances of existing methods. The proposed method requires a few additional gates for each measurement, namely one Hadamard gate, one phase gate and at most n−1 CNOT gates. Experimental results on an IBM-Q system show the computational efficiency and scalability of the proposed scheme, compared with existing state-of-the-art approaches. Code is available at https://github.com/ToyotaCRDL/extended-bell-measurements.

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44

WISEMAN, H. M. "FEEDBACK IN OPEN QUANTUM SYSTEMS". Modern Physics Letters B 09, n. 11n12 (20 maggio 1995): 629–54. http://dx.doi.org/10.1142/s0217984995000590.

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Abstract (sommario):

Open quantum systems continually lose information to their surroundings. In some cases this information can be readily retrieved from the environment and put to good use by engineering a feedback loop to control the system dynamics. Two cases are distinguished: one where the feedback mechanism involves a measurement of the environment, and the other where no measurement is made. It is shown that the latter case can always replicate the former, but not vice versa. This emphasizes the quantum nature of the information being fed back. Two approaches are used to describe the feedback: quantum trajectories (which apply only for feedback based on measurement) and quantum Langevin equations (which can be used in either case), and the results are shown to be equivalent. The obvious applications for the theory are in quantum optics, where the information is lost by radiation damping and can be retrieved by photodetection. A few examples are discussed, one of which is particularly interesting as it has no classical counterpart.

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45

Sierant, Piotr, Giuliano Chiriacò, Federica M. Surace, Shraddha Sharma, Xhek Turkeshi, Marcello Dalmonte, Rosario Fazio e Guido Pagano. "Dissipative Floquet Dynamics: from Steady State to Measurement Induced Criticality in Trapped-ion Chains". Quantum 6 (2 febbraio 2022): 638. http://dx.doi.org/10.22331/q-2022-02-02-638.

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Quantum systems evolving unitarily and subject to quantum measurements exhibit various types of non-equilibrium phase transitions, arising from the competition between unitary evolution and measurements. Dissipative phase transitions in steady states of time-independent Liouvillians and measurement induced phase transitions at the level of quantum trajectories are two primary examples of such transitions. Investigating a many-body spin system subject to periodic resetting measurements, we argue that many-body dissipative Floquet dynamics provides a natural framework to analyze both types of transitions. We show that a dissipative phase transition between a ferromagnetic ordered phase and a paramagnetic disordered phase emerges for long-range systems as a function of measurement probabilities. A measurement induced transition of the entanglement entropy between volume law scaling and sub-volume law scaling is also present, and is distinct from the ordering transition. The two phases correspond to an error-correcting and a quantum-Zeno regimes, respectively. The ferromagnetic phase is lost for short range interactions, while the volume law phase of the entanglement is enhanced. An analysis of multifractal properties of wave function in Hilbert space provides a common perspective on both types of transitions in the system. Our findings are immediately relevant to trapped ion experiments, for which we detail a blueprint proposal based on currently available platforms.

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46

Ezziane, Zoheir. "Quantum computing measurement and intelligence". International Journal of Quantum Chemistry 110, n. 5 (3 giugno 2009): 981–92. http://dx.doi.org/10.1002/qua.22056.

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47

Wang, Ci-Yu, Jun Gao, Zhi-Qiang Jiao, Lu-Feng Qiao, Ruo-Jing Ren, Zhen Feng, Yuan Chen et al. "Integrated measurement server for measurement-device-independent quantum key distribution network". Optics Express 27, n. 5 (20 febbraio 2019): 5982. http://dx.doi.org/10.1364/oe.27.005982.

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48

Bravyi, Sergey, e Robert Konig. "Classical simulation of dissipative fermionic linear optics". Quantum Information and Computation 12, n. 11&12 (novembre 2012): 925–43. http://dx.doi.org/10.26421/qic12.11-12-2.

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Abstract (sommario):

Fermionic linear optics is a limited form of quantum computation which is known to be efficiently simulable on a classical computer. We revisit and extend this result by enlarging the set of available computational gates: in addition to unitaries and measurements, we allow dissipative evolution governed by a Markovian master equation with linear Lindblad operators. We show that this more general form of fermionic computation is also simulable efficiently by classical means. Given a system of $N$~fermionic modes, our algorithm simulates any such gate in time $O(N^3)$ while a single-mode measurement is simulated in time $O(N^2)$. The steady state of the Lindblad equation can be computed in time $O(N^3)$.

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49

Amin, Syed Tahir, e Aeysha Khalique. "Practical quantum teleportation of an unknown quantum state". Canadian Journal of Physics 95, n. 5 (maggio 2017): 498–503. http://dx.doi.org/10.1139/cjp-2016-0758.

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We present our model to teleport an unknown quantum state using entanglement between two distant parties. Our model takes into account experimental limitations due to contribution of multi-photon pair production of parametric down conversion source, inefficiency, dark counts of detectors, and channel losses. We use a linear optics setup for quantum teleportation of an unknown quantum state by the sender performing a Bell state measurement. Our theory successfully provides a model for experimentalists to optimize the fidelity by adjusting the experimental parameters. We apply our model to a recent experiment on quantum teleportation and the results obtained by our model are in good agreement with the experimental results.

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50

Krasionov, I. I., e L. V. Il’ichev. "Noise-oriented quantum optical gyrometry". Quantum Electronics 52, n. 2 (1 febbraio 2022): 127–29. http://dx.doi.org/10.1070/qel17979.

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Abstract By the example of an optical gyroscope scheme, a new method for improving the accuracy of phase measurements is considered. In the rotation-recording Mach – Zehnder interferometer, a two-mode squeezed vacuum is used as an input state. This does not allow realising the traditional scheme, since the average value of the difference signal at the output is always zero. However, it is shown that information about the magnitude of the rotation angular velocity of the instrument reference frame is contained in the noise level of the difference signal. The possibility of reaching the Heisenberg limit of the measurement accuracy is demonstrated.

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