Search results for "Wigner distribution function"
showing 10 items of 36 documents
Quantum erasure within the optical Stern-Gerlach model
2005
In the optical Stern-Gerlach effect the two branches in which the incoming atomic packet splits up can display interference pattern outside the cavity when a field measurement is made which erases the which-way information on the quantum paths the system can follow. On the contrary, the mere possibility to acquire this information causes a decoherence effect which cancels out the interference pattern. A phase space analysis is also carried out to investigate on the negativity of the Wigner function and on the connection between its covariance matrix and the distinguishability of the quantum paths.
Steady-state generation of negative-Wigner-function light using feedback
2016
We propose a method of producing steady-state coherent light with negative Wigner functions in nonlinear media combined with feedback control. While the nonlinearities are essential to produce the Wigner negativities, this alone is insufficient to stabilize steady-state light with negativities. Using feedback control to control the phase in the cavity, we find that this produces significant total negativities for reasonable experimental parameters. The negative Wigner function is produced continuously and does not appear to be restricted to low-amplitude light. The technique is applicable to systems such as exciton-polaritons, where strong natural nonlinearities are present.
All-Optical Storage of Phase-Sensitive Quantum States of Light.
2019
We experimentally demonstrate storage and on-demand release of phase-sensitive, photon-number superposition states of the form $\alpha |0\rangle + \beta e^{i\theta} |1\rangle$ for an optical quantized oscillator mode. For this purpose, we introduce a phase-probing mechanism to a storage system composed of two concatenated optical cavities, which was previously employed for storage of phase-insensitive single-photon states [Phys. Rev. X 3, 041028 (2013)]. This is the first demonstration of all-optically storing highly nonclassical and phase-sensitive quantum states of light. The strong nonclassicality of the states after storage becomes manifest as a negative region in the corresponding Wign…
Decoherence effects in the Stern-Gerlach experiment using matrix Wigner functions
2016
We analyze the Stern-Gerlach experiment in phase space with the help of the matrix Wigner function, which includes the spin degree of freedom. Such analysis allows for an intuitive visualization of the quantum dynamics of the device. We include the interaction with the environment, as described by the Caldeira-Leggett model. The diagonal terms of the matrix provide us with information about the two components of the state that arise from interaction with the magnetic field gradient. In particular, from the marginals of these components, we obtain an analytical formula for the position and momentum probability distributions in the presence of decoherence that shows a diffusive behavior for l…
Reply to Comment on ‘Wigner function for a particle in an infinite lattice’
2013
In a recent paper (2012 New J. Phys. 14 103009), we proposed a definition of the Wigner function for a particle on an infinite lattice. Here we argue that the criticism to our work raised by Bizarro is not substantial and does not invalidate our proposal.
Quantum corrections to the Wigner crystal: A Hartree-Fock expansion
1993
The quantum corrections to the two-dimensional Wigner crystal, for filling \ensuremath{\nu}\ensuremath{\le}1/3, are discussed by using a Hartree-Fock expansion based on wave functions which are (i) related to one another by magnetic translations, (ii) orthonormal, and (iii) strongly localized. Such wave functions are constructed in terms of Gaussians that are localized at the sites of a triangular (Wigner) lattice and have a small overlap c. The ground-state energy per particle is calculated by an expansion in \ensuremath{\surd}\ensuremath{\nu} and in \ensuremath{\delta}\ensuremath{\equiv}${\mathit{c}}^{1/4}$, which is rapidly convergent and stable under the thermodynamical limit. In partic…
Time-energy filtering of single electrons in ballistic waveguides
2019
Characterizing distinct electron wave packets is a basic task for solid-state electron quantum optics with applications in quantum metrology and sensing. A important circuit element for this task is a non-stationary potential barrier than enables backscattering of chiral particles depending on their energy and time of arrival. Here we solve the quantum mechanical problem of single-particle scattering by a ballistic constriction in an fully depleted quantum Hall system under spatially uniform but time-dependent electrostatic potential modulation. The result describes electrons distributed in time-energy space according to a modified Wigner quasiprobability distribution and scattered with an …
The Wigner Distribution of Sum-of-Cissoids and Sum-of-Chirps Processes for the Modelling of Stationary and Non-Stationary Mobile Channels
2016
This paper concerns the time-frequency analysis of stationary and non-stationary multipath flat fading channels. For the modelling of stationary multipath fading channels, we use a sum-of-cisoids (SOCi) process, while the non-stationary channel is modelled by a sum-of-chirps (SOCh) process that captures the time-variant Doppler effect caused by speed variations of the mobile station. For the time-frequency analysis, we apply the concept of the Wigner distribution. Closed-form solutions are provided for the Wigner distribution of SOCi and SOCh processes. It is shown that the obtained Wigner distributions can be expressed by the sum of an auto-term representing the true Doppler power spectral…
Opto-digital tomographic reconstruction of the Wigner distribution function of complex fields.
2008
An optical-digital method has been developed to obtain the Wigner distribution function of one-dimensional complex fields. In this technique an optical setup is employed to experimentally achieve the Radon-Wigner spectrum of the original signal through intensity measurements. Digital tomographic reconstruction is applied to the experimental spectrum to reconstruct the two-dimensional Wigner distribution function of the input. The validity of our proposal is demonstrated with experimental data, and the results are compared with computer simulations.
Synthesis of filters for specified axial irradiance by use of phase–space tomography
2001
A procedure for designing pupil filters for applications where specified axial responses are required is developed. The method is based on the mathematical relationship between the axial impulse response of a system and the Wigner distribution function (WDF) associated to its pupil function. The desired axial irradiance, which can also have a predefined behavior depending on spherical aberration, is used to obtain this WDF by tomographic reconstruction. The synthetic pupil is retrieved from this distribution.