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We review in a unified way a recently proposed method to detect properties of unknown quantum channels and lower bounds to quantum capacities, without resorting to full quantum process tomography. The method is based on the preparation of a…

Quantum Physics · Physics 2017-12-19 Chiara Macchiavello , Massimiliano F. Sacchi

We report an experimental demonstration of effective entanglement in a prepare&measure type of quantum key distribution protocol. Coherent polarization states and heterodyne measurement to characterize the transmitted quantum states are…

Quantum Physics · Physics 2009-11-13 S. Lorenz , J. Rigas , M. Heid , U. L. Andersen , N. Lütkenhaus , G. Leuchs

Entanglement in continuous-variable non-Gaussian states provides irreplaceable advantages in many quantum information tasks. However, the sheer amount of information in such states grows exponentially and makes a full characterization…

A generalized Mach-Zehnder-type interferometer equipped with cross-Kerr elements is proposed to convert N-photon truncated single-mode quantum states into (N+1)-mode single-photon states, which are suitable for further state manipulation by…

Quantum Physics · Physics 2016-05-03 J. Clausen , L. Knoell , D. -G. Welsch

An experimental scheme is introduced to measure multiple parameters that are encoded in the phase quadrature of a light beam. Using a modal description and a spectrally-resolved homodyne detection, it is shown that all of the information is…

Optics · Physics 2017-03-29 Valérian Thiel , Jonathan Roslund , Pu Jian , Claude Fabre , Nicolas Treps

We describe and discuss a recently proposed quantum Monte Carlo algorithm to compute the ground-state properties of various systems of interacting fermions. In this method, the ground state is projected from an initial wave function by a…

Condensed Matter · Physics 2009-10-28 Shiwei Zhang , J. Carlson , J. E. Gubernatis

Intrinsic quantum correlations of weak coherent states are observed between two parties through a novel detection scheme, which can be used as a supplement to the existence decoy-state BB84 and differential phase-shift quantum key…

Quantum Physics · Physics 2011-02-10 Yong Meng Sua , Erin Scanlon , Travis Beaulieu , Viktor Bollen , Kim Fook Lee

We propose and analyze a multi-functional setup consisting of high finesse optical cavities, beam splitters, and phase shifters. The basic scheme projects arbitrary photonic two-mode input states onto the subspace spanned by the product of…

Quantum Physics · Physics 2015-03-13 Anne E. B. Nielsen , Christine A. Muschik , Geza Giedke , K. G. H. Vollbrecht

We report the experimental measurement of bipartite quantum correlations of an unknown two-qubit state. Using a liquid state Nuclear Magnetic Resonance (NMR) setup and employing geometric discord, we evaluate the quantum correlations of a…

Within the dipole approximation we describe the interaction of a photodiode with the quantum electric field. The diode is modelled by an electron in a bound state which upon interaction, treated perturbatively in the paper, can get excited…

Quantum Physics · Physics 2009-11-13 P. Marecki

Learning faithful representations of quantum states is crucial to fully characterizing the variety of many-body states created on quantum processors. While various tomographic methods such as classical shadow and MPS tomography have shown…

Accurately establishing the state of large-scale quantum systems is an important tool in quantum information science; however, the large number of unknown parameters hinders the rapid characterisation of such states, and reconstruction…

Quantum Physics · Physics 2014-07-30 Francesco Tonolini , Susan Chan , Megan Agnew , Alan Lindsay , Jonathan Leach

Determining an unknown quantum state from an ensemble of identical systems is a fundamental, yet experimentally demanding, task in quantum science. Here we study the number of measurement bases needed to fully characterize an arbitrary…

Quantum Physics · Physics 2019-02-11 Leonardo Banchi , W. Steven Kolthammer , M. S. Kim

Quantum dots (QDs) are pivotal for the development of quantum technologies, with applications ranging from single-photon sources for secure communication to quantum computing infrastructures. Understanding the electron dynamics within these…

Quantum Physics · Physics 2024-12-20 Markus Sifft , Johannes C. Bayer , Daniel Hägele , Rolf J. Haug

We precise for the first time the quantum behavior of a measurement apparatus in the framework of the usual interpretation of quantum physics. We show how such a behavior can also be studied by the retrodiction of pre-measurement states…

Quantum Physics · Physics 2010-06-01 Taoufik Amri

We prove that the results of a finite set of general quantum measurements on an arbitrary dimensional quantum system can be simulated using a polynomial (in measurements) number of hidden-variable states. In the limit of infinitely many…

Quantum Physics · Physics 2008-11-11 Borivoje Dakic , Milovan Suvakov , Tomasz Paterek , Caslav Brukner

We demonstrate a new technique for characterizing two-photon quantum states based on joint temporal correlation measurements using time resolved single photon detection by femtosecond upconversion. We measure for the first time the joint…

Quantum Physics · Physics 2009-11-13 Onur Kuzucu , Franco N. C. Wong , Sunao Kurimura , Sergey Tovstonog

We present a model to detect a classical state mixed with an idler photon from a polarization-entangled pair. A weak coherent light with a well-defined polarization, matched in wavelength to the idler photon, is injected into the idler…

Quantum Physics · Physics 2026-02-24 Kim Fook Lee , Prem Kumar

We propose two probabilistic entanglement concentration schemes for a single copy of two-mode squeezed vacuum state. The first scheme is based on the off-resonant interaction of a Rydberg atom with the cavity field while the second setup…

Quantum Physics · Physics 2012-08-27 Jaromir Fiurasek , Ladislav Mista, , Radim Filip

Entanglement is recognized as a key resource for quantum computation and quantum cryptography. For quantum metrology, the use of entangled states has been discussed and demonstrated as a means of improving the signal-to-noise ratio. In…

Quantum Physics · Physics 2007-05-23 C. F. Roos , M. Chwalla , K. Kim , M. Riebe , R. Blatt