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Projective measurement is a commonly used assumption in quantum mechanics. However, advances in quantum measurement techniques allow for partial measurements, which accurately estimate state information while keeping the wavefunction…

Quantum Physics · Physics 2021-08-24 Jonathan Monroe

Entanglement detection is one of the most conventional tasks in quantum information processing. While most experimental demonstrations of high-dimensional entanglement rely on fidelity-based witnesses, these are powerless to detect…

Entanglement enables many promising applications in quantum technology. Devising new generation methods and harnessing entanglement are prerequisites for practical applications. Here we realize a distinct polarization-entangled source by…

Quantum Physics · Physics 2024-02-29 Ming-Yuan Gao , Yin-Hai Li , Zhao-Qi-Zhi Han , Qiang Zhou , Guang-Can Guo , Zhi-Yuan Zhou , Bao-Sen Shi

We theoretically and experimentally investigate conditional enhancement of overall coherence of quantum states by probabilistic quantum operations that apply to the input state a quantum filter diagonal in the basis of incoherent states. We…

Quantum Physics · Physics 2021-08-03 Robert Stárek , Michal Mičuda , Michal Kolář , Radim Filip , Jaromír Fiurášek

In this work, we present a practical and efficient framework for verifying entangled states when only a tomographically incomplete measurement setting is available-specifically, when access to observables is severely limited. We show how…

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…

We demonstrate that non-linear entanglement witnesses can be made particularly useful for entanglement detection in hyper-entangled or multilevel states. We test this idea experimentally on the platform of linear optics using a…

Quantum Physics · Physics 2018-09-12 Vojtěch Trávníček , Karol Bartkiewicz , Antonín Černoch , Karel Lemr

Generating quantum entanglement is not only an important scientific endeavor, but will be essential to realizing quantum-enhanced technologies, in particular, quantum-enhanced measurements with precision beyond classical limits. We…

Quantum Physics · Physics 2011-10-24 Jonathan C. F. Matthews , Alberto Politi , Damien Bonneau , Jeremy L. O'Brien

While measuring the orbital angular momentum state of bright light beams can be performed using imaging techniques, a full characterization at the single-photon level is challenging. For applications to quantum optics and quantum…

Quantum Physics · Physics 2015-04-08 Adrien Nicolas , Lucile Veissier , Elisabeth Giacobino , Dominik Maxein , Julien Laurat

Fault-tolerant quantum computation can be achieved by creating constant-sized, entangled resource states and performing entangling measurements on subsets of their qubits. Linear optical quantum computers can be designed based on this…

Quantum Physics · Physics 2026-02-03 Brendan Pankovich , Alex Neville , Angus Kan , Srikrishna Omkar , Kwok Ho Wan , Kamil Brádler

Programmable photonic quantum processors face a critical challenge: despite significant advances in quantum state preparation and manipulation, measurements remain limited to projective techniques. Here, we demonstrate a programmable…

The generation and detection of maximally-entangled two-particle states, `Bell states,' are crucial tasks in many quantum information protocols such as cryptography and teleportation. Unfortunately, they require strong inter-particle…

Quantum Physics · Physics 2017-08-23 K. J. Resch , J. S. Lundeen , A. M. Steinberg

We show a simple and systematic way to certify any given bipartite state as the unique joint $1$-eigenstate of two separable projectors, each of which can be measured with simple local observables. This is practically useful, as the…

Quantum Physics · Physics 2025-12-18 Jennifer Ahiable , Andreas Winter

This thesis is concerned with retrodiction and measurement in quantum optics. The latter of these two concepts is studied in particular form with a general optical multiport device, consisting of an arbitrary array of beam-splitters and…

Quantum Physics · Physics 2007-05-23 K. L. Pregnell

We describe a direct method to determine the negativity of an arbitrary two-qubit state in experiments. The method is derived by analyzing the relation between the purity, negativity, and a universal entanglement witness for two-qubit…

Quantum Physics · Physics 2015-04-13 Karol Bartkiewicz , Jiří Beran , Karel Lemr , Michał Norek , Adam Miranowicz

High-dimensional entanglement in the form of transverse spatial correlation between a pair of photons generated via spontaneous parametric downconversion is not only a valuable resource in many academic and real-life applications but also…

Quantum Physics · Physics 2025-08-18 Rounak Chatterjee , Vikas S Bhat , Kiran Bajar , Sushil Mujumdar

A simple experimental setup consisting of a spontaneous parametric down-conversion source and passive linear optics is proposed for conditional preparation of a maximally entangled polarization state of two photons. Successful preparation…

Quantum Physics · Physics 2009-11-07 C. Sliwa , K. Banaszek

In recent years, there has been heightened interest in quantum teleportation, which allows for the transfer of unknown quantum states over arbitrary distances. Quantum teleportation not only serves as an essential ingredient in…

We show how to make event-ready multi-partite entanglement between qubits which may be encoded on photons or matter systems. Entangled states of matter systems, which can also act as single photon sources, can be generated using the…

Quantum Physics · Physics 2009-11-11 Pieter Kok , Sean D. Barrett , Timothy P. Spiller

Measuring entanglement is a demanding task in the field of quantum computation and quantum information theory. Recently, some authors experimentally demonstrated an embedding quantum simulator, using it to efficiently measure two-qubit…

Quantum Physics · Physics 2018-11-01 Saeed Haddadi , Mohammad Bohloul