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A new qubit tomography protocol is introduced, based on a continuous positive operator valued measure, which is supported by the set of pure states, and equivariant under the symmetry group SO(3,R) of the qubit state space. Thus the sample…

Quantum Physics · Physics 2008-03-14 Tamás Tasnádi

In the absence of experimental constraints, optimal measurement schemes for quantum state tomography are well understood. We consider the scenario where the experimenter doesn't have arbitrary freedom to construct their measurement set, and…

Quantum Physics · Physics 2014-01-22 Mohammadreza Mohammadi , Agata M. Branczyk

Quantum states are successfully reconstructed using the maximum likelihood estimation on the subspace where the measured projectors reproduce the identity operator. Reconstruction corresponds to normalization of incompatible observations.…

Quantum Physics · Physics 2008-11-26 Z. Hradil , J. Summhammer , H. Rauch

We consider the problem of detecting the true quantum state among $r$ possible ones, based of measurements performed on $n$ copies of a finite-dimensional quantum system. A special case is the problem of discriminating between $r$…

Quantum Physics · Physics 2012-05-14 Michael Nussbaum , Arleta Szkoła

We give a technique to reduce the error probability of quantum algorithms that determine whether its input has a specified property of interest. The standard process of reducing this error is statistical processing of the results of…

Computational Complexity · Computer Science 2019-07-24 Debajyoti Bera , Tharrmashastha P.

We propose an iterative algorithm for incomplete quantum process tomography, with the help of quantum state estimation, based on the combined principles of maximum-likelihood and maximum-entropy. The algorithm yields a unique estimator for…

Quantum Physics · Physics 2012-01-04 Yong Siah Teo , Berthold-Georg Englert , Jaroslav Rehacek , Zdenek Hradil

We report on an intrinsic relationship between the maximum-likelihood quantum-state estimation and the representation of the signal. A quantum analogy of the transfer function determines the space where the reconstruction should be done…

Quantum Physics · Physics 2009-11-13 Z. Hradil , D. Mogilevtsev , J. Rehacek

Time-resolved studies of quantum systems are the key to understand quantum dynamics at its core. The real-time measurement of individual quantum numbers as they switch between certain discrete values, well known as random telegraph signal,…

Mesoscale and Nanoscale Physics · Physics 2022-03-02 Eric Kleinherbers , Philipp Stegmann , Annika Kurzmann , Martin Geller , Axel Lorke , Jürgen König

Quantum error mitigation has been proposed as a means to combat unwanted and unavoidable errors in near-term quantum computing without the heavy resource overheads required by fault tolerant schemes. Recently, error mitigation has been…

Quantum Physics · Physics 2024-10-15 Yihui Quek , Daniel Stilck França , Sumeet Khatri , Johannes Jakob Meyer , Jens Eisert

It is generally assumed that every process in quantum physics can be described mathematically by a completely positive map. However, experimentally reconstructed processes are not necessarily completely positive due to statistical or…

Quantum Physics · Physics 2019-01-23 Sabine Wölk , Theeraphot Sriarunothai , Gouri S. Giri , Christof Wunderlich

Common tools for obtaining physical density matrices in experimental quantum state tomography are shown here to cause systematic errors. For example, using maximum likelihood or least squares optimization for state reconstruction, we…

Quantum tomography is a process of quantum state reconstruction using data from multiple measurements. An essential goal for a quantum tomography algorithm is to find measurements that will maximize the useful information about an unknown…

Quantum Physics · Physics 2020-08-05 A. D. Moiseevskiy , G. I. Struchalin , S. S. Straupe , S. P. Kulik

We extend the concept of probabilistic unambiguous discrimination of quantum states to quantum state estimation. We consider a scenario where the measurement device can output either an estimate of the unknown input state or an inconclusive…

Quantum Physics · Physics 2009-11-13 Jaromir Fiurasek

We introduce an operational and statistically meaningful measure, the quantum tomographic transfer function, that possesses important physical invariance properties for judging whether a given informationally complete quantum measurement…

Quantum Physics · Physics 2019-07-31 Jaroslav Rehacek , Yong Siah Teo , Zdenek Hradil

Syndrome measurements made in quantum error correction contain more information than is typically used. We show that the statistics of data from syndrome measurements can be used to do the following: (i) estimation of parameters of an error…

Quantum tomography makes it possible to obtain comprehensive information about certain logical elements of a quantum computer. In this regard, it is a promising tool for debugging quantum computers. The practical application of tomography,…

Quantum Physics · Physics 2020-12-23 B. I. Bantysh , Yu. I. Bogdanov

Quantum-enhanced measurements exploit quantum mechanical effects to provide ultra-precise estimates of physical variables for use in advanced technologies, such as frequency calibration of atomic clocks, gravitational waves detection, and…

Quantum Physics · Physics 2014-07-28 J. Calsamiglia , B. Gendra , R. Munoz-Tapia , E. Bagan

Verifying entanglement between parties is essential for creating secure quantum communication. However, finite statistics can lead to false positive outcomes in any tests for entanglement. Here, we introduce a one-sided device-independent…

Quantum metrology is a general term for methods to precisely estimate the value of an unknown parameter by actively using quantum resources. In particular, some classes of entangled states can be used to significantly suppress the…

Quantum Physics · Physics 2015-05-01 Takanori Sugiyama

We show that quantum state tomography with perfect knowledge of the measurement apparatus proves to be, in some instances, inferior to strategies discarding all information about the measurement at hand, as in the case of data pattern…

Quantum Physics · Physics 2021-08-11 L. Motka , M. Paur , J. Rehacek , Z. Hradil , L. L. Sanchez-Soto