Quantum tomograph for measurement and characterization of quantum states of biphoton sources

2020 ◽  
pp. 20-26
Author(s):  
Dmitry N. Frolovtsev ◽  
Sergey A. Magnitskiy ◽  
Andrey V. Demin
Keyword(s):  
Density Matrix ◽  
Quantum State ◽  
Measurement Errors ◽  
Quantum Tomography ◽  
Statistical Characteristics ◽  
Light Sources ◽  
Matrix Elements ◽  
Experimental Implementation

The method and prototype of a device for characterizing of biphoton light sources based on spontaneous parametric downdonversion by quantum tomography are described. The prototype is an experimental implementation of a specialized quantum tomograph designed to measure the quantum polarization states of radiation generated by biphoton sources. Specially developed software will determine the statistical characteristics of the measured quantum state, calculate the tomographic and likelihood estimations of the density matrix, calculate the measurement errors of the density matrix elements and evaluate the quality of the quantum state of biphotons.

Applications of Statistical Characteristics of Geodetic Networks

1974 ◽  
Vol 28 (5) ◽  
pp. 702-708
Author(s):  
L. A. Gale
Keyword(s):  
Observational Data ◽  
Geodetic Network ◽  
Statistical Information ◽  
Statistical Characteristics ◽  
Geodetic Networks ◽  
Control File ◽  
Geodetic Control ◽  
Inner Constraint

Numerous statistics that can be obtained from the processing of the observations and the adjustment of a geodetic network can be used to assess the quality of the network and the observational data. The processes used for assessment and planning depend on the needs and the capabilities of the user. Statistical information derived from nonsingular vis-à-vis singular (“inner-constraint”) adjustments is discussed. Standards for the characterization of the quality of networks are reviewed. Suggestions are made on the type of information that should be directly available from a geodetic control file.

scholarly journals Global convergence of diluted iterations in maximum-likelihood quantum tomography

2014 ◽  
Vol 14 (11&12) ◽  
pp. 966-980
Author(s):  
Doglas S. Goncalves ◽  
Marcia A. Gomes-Ruggiero ◽  
Carlile Lavor
Keyword(s):  
Maximum Likelihood ◽  
Global Convergence ◽  
Density Matrix ◽  
Quantum State ◽  
Maximum Likelihood Estimate ◽  
Quantum Tomography ◽  
Practical Implementation ◽  
Globally Convergent ◽  
State Tomography ◽  
New Interpretation

In this paper we address convergence issues of the Diluted $R \rho R$ algorithm \cite{rehacek2007}, used to obtain the maximum likelihood estimate for the density matrix in quantum state tomography. We give a new interpretation to the diluted $R \rho R$ iterations that allows us to prove the global convergence under weaker assumptions. Thus, we propose a new algorithm which is globally convergent and suitable for practical implementation.

The Test Method Research of Electric Light Sources Parameters and Detection of Uncertainty Evaluation

2011 ◽  
Vol 130-134 ◽  
pp. 4114-4117
Author(s):  
Xiao Ling Wang ◽  
Xue Yao Qian ◽  
Zhyingi Dai
Keyword(s):  
Test Method ◽  
Laboratory Measurement ◽  
Light Sources ◽  
Calibration Laboratory ◽  
Quality Of Results ◽  
Wide Range ◽  
Measurement Results ◽  
Important Basis

Characterization of measurement uncertainty as a measure of quality of results, and obtained in the metrology of a wide range of applications. At all levels of certified calibration laboratory measurement, measurement standards of the establishment of technical reports, or identification certificate issued by the calibration and so on, require a higher level in the measuring results are given to provide the corresponding uncertainty. Measuring the quality of the results of the measurement results is a measure of the credibility of an important basis. In this paper, through concrete examples and laboratory measurement of electrical parameters of the light source of the data obtained, the Evaluation of Uncertainty.

scholarly journals The complexity of stoquastic local Hamiltonian problems

2008 ◽  
Vol 8 (5) ◽  
pp. 361-385
Author(s):  
S. Bravyi ◽  
D.P. DiVincenzo ◽  
R. Oliveira ◽  
B.M. Terhal
Keyword(s):  
Density Matrix ◽  
Spectral Gap ◽  
Natural World ◽  
Matrix Elements ◽  
Hamiltonian Problems ◽  
Adiabatic Quantum Computation ◽  
Equivalent Characterization ◽  
Probabilistic Version ◽  
Special Case

We study the complexity of the Local Hamiltonian Problem (denoted as LH-MIN) in the special case when a Hamiltonian obeys the condition that all off-diagonal matrix elements in the standard basis are real and non-positive. We will call such Hamiltonians, which are common in the natural world, stoquastic. An equivalent characterization of stoquastic Hamiltonians is that they have an entry-wise non-negative Gibbs density matrix for any temperature. We prove that LH-MIN for stoquastic Hamiltonians belongs to the complexity class \AM{}--- a probabilistic version of \NP{} with two rounds of communication between the prover and the verifier. We also show that $2$-local stoquastic LH-MIN is hard for the class \MA. With the additional promise of having a polynomial spectral gap, we show that stoquastic LH-MIN belongs to the class \POSTBPP=\BPPpath --- a generalization of \BPP{} in which a post-selective readout is allowed. This last result also shows that any problem solved by adiabatic quantum computation using stoquastic Hamiltonians is in PostBPP.

scholarly journals Attention-based Quantum Tomography

2021 ◽  
Author(s):  
Peter Junghwa Cha ◽  
Paul Ginsparg ◽  
Felix Wu ◽  
Juan Felipe Carrasquilla ◽  
Peter L. McMahon ◽  
...  
Keyword(s):  
Neural Network ◽  
Natural Language Processing ◽  
Natural Language ◽  
Density Matrix ◽  
Quantum State ◽  
Language Processing ◽  
Quantum Tomography ◽  
Neural Network Models ◽  
State Reconstruction ◽  
Quantum State Reconstruction

Abstract With rapid progress across platforms for quantum systems, the problem of many-body quantum state reconstruction for noisy quantum states becomes an important challenge. There has been a growing interest in approaching the problem of quantum state reconstruction using generative neural network models. Here we propose the ``Attention-based Quantum Tomography'' (AQT), a quantum state reconstruction using an attention mechanism-based generative network that learns the mixed state density matrix of a noisy quantum state. AQT is based on the model proposed in ``Attention is all you need" by Vaswani, et al. (2017) that is designed to learn long-range correlations in natural language sentences and thereby outperform previous natural language processing models. We demonstrate not only that AQT outperforms earlier neural-network-based quantum state reconstruction on identical tasks but that AQT can accurately reconstruct the density matrix associated with a noisy quantum state experimentally realized in an IBMQ quantum computer. We speculate the success of the AQT stems from its ability to model quantum entanglement across the entire quantum system much as the attention model for natural language processing captures the correlations among words in a sentence.

scholarly journals The Measure Aspect of Quantum Uncertainty, of Entanglement, and the Associated Entropies

2021 ◽  
Vol 3 (3) ◽  
pp. 534-548
Author(s):  
Ivan Horváth
Keyword(s):  
Number Theory ◽  
Density Matrix ◽  
Quantum State ◽  
Degrees Of Freedom ◽  
Minimal Amount ◽  
Effective Number ◽  
Quantum Uncertainty ◽  
Commuting Operators ◽  
Central Result

Indeterminacy associated with the probing of a quantum state is commonly expressed through spectral distances (metric) featured in the outcomes of repeated experiments. Here, we express it as an effective amount (measure) of distinct outcomes instead. The resulting μ-uncertainties are described by the effective number theory whose central result, the existence of a minimal amount, leads to a well-defined notion of intrinsic irremovable uncertainty. We derive μ-uncertainty formulas for arbitrary set of commuting operators, including the cases with continuous spectra. The associated entropy-like characteristics, the μ-entropies, convey how many degrees of freedom are effectively involved in a given measurement process. In order to construct quantum μ-entropies, we are led to quantum effective numbers designed to count independent, mutually orthogonal states effectively comprising a density matrix. This concept is basis-independent and leads to a measure-based characterization of entanglement.

The Influence Of The Led Luminaires Electrical Parameters On Their Correlated Colour Temperature During Operation Mode

2020 ◽  
pp. 89-96
Author(s):  
Sergei S. Kapitonov ◽  
Alexei S. Vinokurov ◽  
Sergei V. Prytkov ◽  
Sergei Yu. Grigorovich ◽  
Anastasia V. Kapitonova ◽  
...  
Keyword(s):  
Operation Mode ◽  
Light Sources ◽  
Electrical Parameters ◽  
Colour Temperature ◽  
Radiation Spectra ◽  
Service Period ◽  
Close Proximity ◽  
Definition Of ◽  
Comprehensive Study

The article describes the results of comprehensive study aiming at increase of quality of LED luminaires and definition of the nature of changes in their correlated colour temperature (CCT) in the course of operation. Dependences of CCT of LED luminaires with remote and close location of phosphor for 10 thousand hours of operation in different electric modes were obtained; the results of comparison between the initial and final radiation spectra of the luminaires are presented; using mathematical statistics methods, variation of luminaire CCT over the service period claimed by the manufacturer is forecast; the least favourable electric operation modes with the highest CCT variation observed are defined. The obtained results have confirmed availability of the problem of variation of CCT of LED luminaires during their operation. Possible way of its resolution is application of more qualitative and therefore expensive LEDs with close proximity of phosphor or LEDs with remote phosphor. The article may be interesting both for manufacturers and consumers of LED light sources and lighting devices using them.

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