We propose a scheme for optimal Gaussian purification of coherent states<br> from several imperfect copies. The proposal is experimentally<br> demonstrated for the case of two copies of a coherent state sent through<br> independent noisy channels. Our purification protocol relies on only<br> linear optics and an ancilla vacuum state, rendering this approach an<br> interesting alternative to the more complex protocols of entanglement<br> distillation and quantum error correction.
Quantum information processing and communication - Strategic report on current status, visions and goals for research in Europe
P Zoller,
T Beth,
D Binosi,
R Blatt,
H Briegel,
D Bruss,
T Calarco,
JI Cirac,
D Deutsch, et al.
EUROPEAN PHYSICAL JOURNAL D
36
(2)
203-228
(2005)
| Journal
We present an excerpt of the document "Quantum Information Processing and Communication: Strategic report on current status, visions and goals for research in Europe", which has been recently published in electronic form at the website of FET (the Future and Emerging Technologies Unit of the Directorate General Information Society of the European Commission, http://www.cordis.lu/ist/fet/qipc-sr.htm). This document has been elaborated, following a former suggestion by FET, by a committee of QIPC scientists to provide input towards the European Commission for the preparation of the Seventh Framework Program. Besides being a document addressed to policy makers and funding agencies (both at the European and national level), the document contains a detailed scientific assessment of the state-of-the-art, main research goals, challenges, strengths, weaknesses, visions and perspectives of all the most relevant QIPC sub-fields, that we report here.
Generation of a radially polarized doughnut mode of high quality
We present an experimental set-up to generate laser beams with locally varying polarization distribution. In a linear set-up, a radially polarized beam of high quality regarding intensity distribution, polarization and phase-front distortion is generated. This beam can be used for tight focusing. Further applications are discussed.
Unconditional quantum cloning of coherent states with linear optics
A scheme for optimal Gaussian cloning of optical coherent states is proposed and experimentally demonstrated. Its optical realization is based entirely on simple linear optical elements and homodyne detection. The optimality of the presented scheme is limited only by detection inefficiencies. Experimentally, we achieved a cloning fidelity of about 65%, which almost touches the optimal value of 2/3.
Demonstration of the spatial separation of the entangled quantum sidebands of an optical field
EH Huntington,
GN Milford,
C Robilliard,
TC Ralph,
O Glockl,
Ulrik L. Andersen,
S Lorenz,
Gerd Leuchs
Quantum optics experiments on "bright" beams are based on the spectral analysis of field fluctuations and typically probe correlations between radio-frequency sideband modes. However, the extra degree of freedom represented by this dual-mode picture is generally ignored. We demonstrate the experimental operation of a device which can be used to separate the quantum sidebands of an optical field. We use this device to explicitly demonstrate the quantum entanglement between the sidebands of a squeezed beam.
The effect of dissipation on nonclassical states of the radiation field
G Leuchs,
UL Andersen
LASER PHYSICS
15
(1)
129-134
(2005)
We point out similarities in the evolution of different types of nonclassical light fields. Generally, Fock and cat states are considered to decay much faster under dissipation than do squeezed states. We connect measurements of the intensity correlation function of nonclassical light to the second moment of the photon number distribution function. It is shown that all these nonclassical fields behave in a similar manner when one is looking at an appropriate property. Finally it is shown how the electronic-detection noise floor, typically present in measurements of the variance of a photocurrent, can be eliminated based upon a procedure that is well-established for intensity correlation measurements.
Optimum splitting ratio for amplifier noise reduction by an asymmetric
nonlinear optical loop mirror
We theoretically and experimentally analyze the influence of the splitting ratio and the input power on the noise reduction capability of an asymmetric nonlinear optical loop mirror (NOLM) for different input noise levels. An easy method to calculate the optimum parameters for noise reduction is also presented. The best noise reduction is found at NOLM input powers at which the nonlinear transfer function has a slope close to zero. Additionally, the splitting ratio of the NOLM has to be adapted to its input noise level to suppress amplitude fluctuations effectively. Since the noise reduction by the NOLM is due to the Kerr nonlinearity, which has a timescale below a few femtoseconds, the noise reduction is applicable to short pulses in the picosecond and femtosecond range. This makes the NOLM applicable as an optical regenerator in an optical data transmission system at high bit rates, such as 160 GBit/s.
NOLM-based RZ-DPSK signal regeneration
AG Striegler,
M Meissner,
K Cvecek,
K Sponsel,
G Leuchs,
B Schmauss
We present a nonlinear optical loop mirror (NOLM)-based 2R-regenerator setup, which signals modulated in phase-sensitive modulation formats. In a conventional NOLM, fluctuations of the signal amplitude are converted into phase fluctuations. Therefore, it is not suitable for regeneration of signals, modulated in formats such as differential phase-shift keying (DPSK) or duobinary. In this letter, we present a modified NOLM setup for 2R-regeneration taking return-to-zero DPSK as an example.
Efficient polarization squeezing in optical fibers
We report on a novel and efficient source of polarization squeezing that uses a single pass through an optical fiber. Using the fiber's two orthogonal polarization axes produces two identical squeezed beams. Combining these in a Stokes measurement generates polarization squeezing of up to 5.1 &PLUSMN; 0.3 dB. Furthermore, this scheme enables us to directly measure, for both polarizations, the noise of any given quadrature. © 2005 Optical Society of America.
MPL Research Centers and Schools
Data Collection
This website uses cookies to ensure you get the best experience on our website.
