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Quantum emitters in solid-state crystals have recently attracted a lot of attention due to their simple applicability in optical quantum technologies. The polarization of single photons generated by quantum emitters is one of the key…

We look at generalisations of sets of vectors proving the Kochen-Specker theorem in 3 and 4 dimensions. It has been shown that two such sets, although unitarily inequivalent, are part of a larger 3-parameter family of vectors that share the…

Quantum Physics · Physics 2015-05-19 Kate Blanchfield

Upon entangling a spatial binary alternative of a photon with its polarization, one can use single photons to study arbitrary 2-qubit states. Sending the photon through a Mach-Zehnder interferometer, equipped with sets of wave plates that…

Quantum Physics · Physics 2009-11-07 Berthold-Georg Englert , Christian Kurtsiefer , Harald Weinfurter

Unsharp spin 1 observables arise from the fact that a residual uncertainty about the actual orientation of the measurement device remains. If the uncertainty is below a certain level, and if the distribution of measurement errors is…

Quantum Physics · Physics 2009-11-07 Thomas Breuer

We present the first experimental demonstration of the ''optimal'' and ''universal'' quantum entangling process involving qubits encoded in the polarization of single photons. The structure of the ''quantum entangling machine'' consists of…

Quantum Physics · Physics 2009-11-10 Fabio Sciarrino , Francesco De Martini , Vladimir Buzek

We propose an experiment that realizes a symmetric informationally complete (SIC) probability-operator measurement (POM) in the four-dimensional Hilbert space of a qubit pair. The qubit pair is carried by a single photon as a polarization…

Quantum Physics · Physics 2015-06-04 Amir Kalev , Jiangwei Shang , Berthold-Georg Englert

Spatial light modulators are versatile devices employed in a vast range of applications to modify the transverse phase or amplitude profile of an incident light beam. Most experiments are designed to use a specific polarization which…

Quantum Physics · Physics 2014-05-06 G. Barreto Lemos , J. O. de Almeida , S. P. Walborn , P. H. Souto Ribeiro , M. Hor-Meyll

A universal and optimal method for the polarimetry of light with arbitrary photon statistics is presented. The method is based on the continuous maximum-likelihood positive operator-valued measure (ML-POVM) for pure polarization states over…

Quantum Physics · Physics 2016-04-20 Lu Zhang , Kam Wai Clifford Chan , Pramode K. Verma

We present, and analyze thoroughly, a highly symmetric and efficient scheme for the determination of a single-qubit state, such as the polarization properties of photons emitted by a single-photon source. In our scheme there are only four…

Quantum Physics · Physics 2016-08-16 Jaroslav Řeháček , Berthold-Georg Englert , Dagomir Kaszlikowski

We deal with countable alphabet locally compact random subshifts of finite type (the latter merely meaning that the symbol space is generated by an incidence matrix) under the absence of Big Images Property and under the absence of uniform…

Dynamical Systems · Mathematics 2015-09-02 Volker Mayer , Mariusz Urbanski

We suggest and demonstrate an all-optical quantum simulator for single-qubit noisy channels originating from the interaction with a fluctuating field. The simulator employs the polarization degree of freedom of a single photon, and exploits…

Elaborating on a previous work by Simon et al. [PRL 85, 1783 (2000)] we propose a realizable quantum optical single-photon experiment using standard present day technology, capable of discriminating maximally between the predictions of…

Quantum Physics · Physics 2009-11-07 Jose L. Cereceda

In the paper it is argued that the Kochen-Specker theorem necessitates a conclusion that for a quantum system it is possible to find a set of projection operators which is not truth-value bivalent; that is, a bivalent truth-value assignment…

Quantum Physics · Physics 2017-10-25 Arkady Bolotin

It is commonly believed that the most general type of a quantum-mechanical measurement is one described by a positive-operator valued measure (POVM). In the present paper, this statement is proven for any measurements on quantum systems…

Quantum Physics · Physics 2014-02-13 A. V. Nenashev

We report on two optical realizations of the $1 \to 2$ asymmetric phase-covariant cloning machines for polarization states of single photons. The experimental setups combine two-photon interference and tunable polarization filtering that…

Quantum Physics · Physics 2009-11-13 Jan Soubusta , Lucie Bartuskova , Antonin Cernoch , Miloslav Dusek , Jaromir Fiurasek

A suitable generalized measurement described by a 4-element positive operator-valued measure (POVM) on each particle of a two-qubit system in the singlet state is, from the point of view of Einstein, Podolsky, and Rosen's (EPR's) criterion…

Quantum Physics · Physics 2009-07-28 Adan Cabello

Quantum state tomography is a central technique for the characterization and verification of quantum systems. Standard tomography is widely used for low-dimensional systems, but for larger systems, it becomes impractical due to the…

Photon counting induces an effective nonlinear optical phase shift on certain states derived by linear optics from single photons. Although this no nlinearity is nondeterministic, it is sufficient in principle to allow scalable linear…

Quantum Physics · Physics 2007-05-23 T. C. Ralph , A. P. Lund , H. M. Wiseman

We review and extend recent findings of Godsil and Zaks, who published a constructive coloring of the rational unit sphere with the property that for any orthogonal tripod formed by rays extending from the origin of the points of the…

Quantum Physics · Physics 2024-02-13 Hans Havlicek , Guenther Krenn , Johann Summhammer , Karl Svozil

The superposition of quantum states lies at the heart of physics and has been recently found to serve as a versatile resource for quantum information protocols, defining the notion of quantum coherence. In this contribution, we report on…

Quantum Physics · Physics 2019-10-16 Valeria Cimini , Ilaria Gianani , Marco Sbroscia , Jan Sperling , Marco Barbieri