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We consider two classes of non-Gaussian entangled states generated from the product of number states with the action of the beamsplitter or the two-mode squeezer. It is shown that, for many of these states, the covariance matrix is…

Quantum Physics · Physics 2012-06-15 Ryo Namiki

Optical loss is a common bottleneck in photonic quantum information processing, undermining the quantum advantage over classical approaches. Although several countermeasures, such as quantum distillation and error correction, have been…

Squeezed states of light have been improving the sensitivity of gravitational-wave observatories and are nonclassical resources of quantum cryptography and envisioned photonic quantum computers. The higher the squeeze factor is, the higher…

Quantum Physics · Physics 2023-01-11 Stephan Grebien , Julian Goettsch , Boris Hage , Jaromir Fiurasek , Roman Schnabel

We present a protocol for generating nonclassical states of atomic spin ensembles through the backaction induced by a hybrid measurement of light that is entangled with atoms, combining both homodyne and single photon detection. In phase-I…

Quantum Physics · Physics 2025-04-02 Andrew Kolmer Forbes , Ivan H. Deutsch

Recently, the fundamental and nanoscale understanding of complex phenomena in materials research and the life sciences, witnessed considerable progress. However, elucidating the underlying mechanisms, governed by entangled degrees of…

Mesoscale and Nanoscale Physics · Physics 2015-08-04 Frederik Kuschewski , Susanne C. Kehr , Bert Green , Christian Bauer , Michael Gensch , Lukas M. Eng

A synchronously pumped optical parametric oscillator (SPOPO) operating at 93 MHz is used to generate squeezed states at 1035 nm. The system features a counter-propagating beam at the same wavelength as the quantum state, which…

We show how to implement several continuous-variable coherent protocols with linear optics. Noise can accumulate when implementing each coherent protocol with realistic optical devices. Our analysis bounds the level of noise accumulation.…

Quantum Physics · Physics 2008-02-22 Mark M. Wilde , Todd A. Brun , Jonathan P. Dowling , Hwang Lee

It is generally assumed that on-off detectors with single-photon sensitivity cannot distinguish coherent states from phase-mixed coherent states without some form of quadrature-based tomography. Here, we show that it is theoretically…

Quantum Physics · Physics 2016-03-22 Samuel R. Hedemann

We show that single-photon entangled states of the form |0>|1>+|1>|0> can be purified with a simple linear-optics based protocol, which is eminently feasible with current technology. Besides its conceptual interest, this result is relevant…

Quantum Physics · Physics 2009-11-13 Nicolas Sangouard , Christoph Simon , Thomas Coudreau , Nicolas Gisin

We propose a solid-state experiment to study the process of continuous quantum measurement of a qubit state. The experiment would verify that an individual qubit stays coherent during the process of measurement (in contrast to the gradual…

Mesoscale and Nanoscale Physics · Physics 2009-10-31 Alexander N. Korotkov

Entanglement distillation transforms weakly entangled noisy states into highly entangled states, a primitive to be used in quantum repeater schemes and other protocols designed for quantum communication and key distribution. In this work,…

Quantum Physics · Physics 2013-04-25 Earl T. Campbell , Marco G. Genoni , Jens Eisert

State transfer across discrete quantum networks is one of the elementary tasks of quantum information processing. Its aim is the faithful placement of information into a specific position in the network. However, all physical systems suffer…

Quantum Physics · Physics 2014-12-30 Holger Frydrych , Antonín Hoskovec , Gernot Alber , Igor Jex

We consider entanglement purification protocols for multiple copies of qubit states. We use high-dimensional auxiliary entangled systems to learn about number and positions of errors in the noisy ensemble in an explicit and controlled way,…

Quantum Physics · Physics 2021-07-28 Ferran Riera Sàbat , Pavel Sekatski , Alexander Pirker , Wolfgang Dür

Nonstationary molecular states which contain electronic coherences can be impulsively created and manipulated by using recently-developed ultrashort optical and X-ray pulses via photoexcitation, photoionization and Auger processes. We…

Chemical Physics · Physics 2015-09-02 Konstantin E. Dorfman , Kochise Bennett , Shaul Mukamel

Pure states are usually used to observe quantum phenomena. In this study, we show that a quantum superposition of spatially displaced mixed cat states can be generated within an optical waveguide via nonparaxial unitary evolution of the…

Quantum Physics · Physics 2025-12-01 N. I. Petrov

We show that conditional output measurement on a beam splitter may be used to produce photon-added states for a large class of signal-mode quantum states, such as thermal states, coherent states, squeezed states, displaced photon-number…

Quantum Physics · Physics 2009-10-30 M. Dakna , L. Knoll , D. -G. Welsch

We report the first experimental realization of pattern formation in a spatially extended nonlinear system when the system is alternated between two states, neither of which exhibits patterning. Dynamical equations modeling the system are…

Pattern Formation and Solitons · Physics 2009-11-11 J. P. Sharpe , P. L. Ramazza , N. Sungar , Karl Saunders

Purification schemes for multi-particle entangled states cannot be treated as straightforward extensions of those for two particles because of the lack of symmetry they possess. We propose purification protocols for a wide range of mixed…

Quantum Physics · Physics 2009-10-30 M. Murao , M. B. Plenio , S. Popescu , V. Vedral , P. L. Knight

We consider a protocol for sharing quantum states using continuous variable systems. Specifically we introduce an encoding procedure where bosonic modes in arbitrary secret states are mixed with several ancillary squeezed modes through a…

Quantum Physics · Physics 2019-08-08 Francesco Arzani , Giulia Ferrini , Frédéric Grosshans , Damian Markham

We experimentally demonstrate a new measurement scheme for the discrimination of two coherent states. The measurement scheme is based on a displacement operation followed by a photon number resolving detector, and we show that it…

Quantum Physics · Physics 2010-10-12 Christoffer Wittmann , Ulrik L. Andersen , Masahiro Takeoka , Denis Sych , Gerd Leuchs