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In quantum-state tomography on sources with quantum degrees of freedom of large Hilbert spaces, inference of quantum states of light for instance, a complete characterization of the quantum states for these sources is often not feasible…

Quantum Physics · Physics 2013-11-14 Yong Siah Teo , Jaroslav Rehacek , Zdenek Hradil

Berry curvature is an imaginary component of the quantum geometric tensor (QGT) and is well studied in many branches of modern physics; however, the quantum metric as a real component of the QGT is less explored. Here, by using tunable…

Quantum state tomography (QST) is plagued by the ``curse of dimensionality'' due to the exponentially-scaled complexity in measurement and data post-processing. Efficient QST schemes for large-scale mixed states are currently missing. In…

Quantum Physics · Physics 2023-08-15 Wen-jun Li , Kai Xu , Heng Fan , Shi-ju Ran , Gang Su

Quantum sensing exploits quantum phenomena to enhance the detection and estimation of classical parameters of physical systems and biological entities, particularly so as to overcome the inefficiencies of its classical counterparts. A…

We briefly review single-qubit quantum process tomography for trace-preserving and nontrace-preserving processes, and derive explicit forms of the general constraints for fitting experimental data. These new forms provide additional insight…

Quantum Physics · Physics 2016-05-31 Ramesh Bhandari , Nicholas A. Peters

Quantum gates and simple quantum algorithms can be designed utilizing the diffraction phenomena of a photon within a multiplexed holographic element. The quantum eigenstates we use are the photon's linear momentum (LM) as measured by the…

Quantum computing shows promise for addressing computationally intensive problems but is constrained by the exponential resource requirements of general quantum state tomography (QST), which fully characterizes quantum states through…

Quantum Physics · Physics 2025-09-12 Hao Su , Shiying Xiong , Yue Yang

Quantum simulators, in which well controlled quantum systems are used to reproduce the dynamics of less understood ones, have the potential to explore physics that is inaccessible to modeling with classical computers. However, checking the…

Quantum Physics · Physics 2015-06-18 C. Senko , J. Smith , P. Richerme , A. Lee , W. C. Campbell , C. Monroe

Quantum signal processing (QSP) and the quantum singular value transformation (QSVT) are pivotal tools for simplifying the development of quantum algorithms. These techniques leverage polynomial transformations on the eigenvalues or…

Quantum Physics · Physics 2024-07-02 Lorenzo Laneve

Quantum tomography is one of the major challenges of large-scale quantum information research due to the exponential time complexity. In this work, we develop and apply a Bayesian state estimation method to experimentally demonstrate…

Quantum Physics · Physics 2025-11-13 Yang Zhengning , Shihao Ru , Lianzhen Cao , Nikolay Zheludev , Weibo Gao

Qubit noise spectroscopy is an important tool for the experimental investigation of open quantum systems. However, conventional techniques for noise spectroscopy are time-consuming, because they require measurements of the noise spectral…

Quantum Physics · Physics 2025-06-24 Kaixin Huang , Demitry Farfurnik , Alireza Seif , Mohammad Hafezi , Yi-Kai Liu

Entanglement is the key feature of many-body quantum systems, and the development of new tools to probe it in the laboratory is an outstanding challenge. Measuring the entropy of different partitions of a quantum system provides a way to…

We investigate the dynamics of electron spin qubits in quantum dots. Measurement of the qubit state is realized by a charge current through the dot. The dynamics is described in the framework of the quantum trajectory approach, widely used…

Mesoscale and Nanoscale Physics · Physics 2009-11-10 Holger Schaefers , Walter T. Strunz

Entanglement is an extraordinary feature of quantum mechanics. Sources of entangled optical photons were essential to test the foundations of quantum physics through violations of Bell's inequalities. More recently, entangled many-body…

Quantum computing architectures require an accurate and efficient description in terms of many-electron states. Recent implementations include quantum dot arrays, where the ground state of a multi q-bit system can be altered by voltages…

Mesoscale and Nanoscale Physics · Physics 2022-09-27 G. A. Nemnes , T. L. Mitran , A. T. Preda , I. Ghiu , M. Marciu , A. Manolescu

Modern thermodynamic theories can be used to study highly complex quantum dynamics. Here, we experimentally demonstrate that the violation of thermodynamic constraints allows to detect the coupling of a quantum system to a hidden…

Quantum Physics · Physics 2021-03-10 Ivan Henao , Raam Uzdin , Nadav Katz

The standard method of Quantum State Tomography (QST) relies on the measurement of a set of noncommuting observables, realized in a series of independent experiments. Ancilla Assisted QST (AAQST) proposed by Nieuwenhuizen and co-workers…

Quantum Physics · Physics 2016-11-26 Abhishek Shukla , K. Rama Koteswara Rao , T. S. Mahesh

We report results on superconducting tunneling spectroscopy of a carbon nanotube quantum dot. Using a three-probe technique that includes a superconducting tunnel probe, we map out changes in conductance due to band structure, excited…

Strongly Correlated Electrons · Physics 2015-05-13 Travis Dirks , Yung-Fu Chen , Norman O. Birge , Nadya Mason

The quantum regression theorem (QRT) is the most-widely used tool for calculating multitime correlation functions for the assessment of quantum emitters. It is an approximate method based on a Markov assumption for the environmental…

Quantum Physics · Physics 2021-12-20 M. Cosacchi , T. Seidelmann , M. Cygorek , A. Vagov , D. E. Reiter , V. M. Axt

Impressive progress has been made in the past decade in the study of technological applications of varied types of quantum systems. With industry giants like IBM laying down their roadmap for scalable quantum devices with more than…

Quantum Physics · Physics 2021-09-15 Rishabh Gupta , Sabre Kais , Raphael D. Levine