2,807 research outputs found
Conditional purity and quantum correlation measures in two qubit mixed states
We analyze and show experimental results of the conditional purity, the
quantum discord and other related measures of quantum correlation in mixed
two-qubit states constructed from a pair of photons in identical polarization
states. The considered states are relevant for the description of spin pair
states in interacting spin chains in a transverse magnetic field. We derive
clean analytical expressions for the conditional local purity and other
correlation measures obtained as a result of a remote local projective
measurement, which are fully verified by the experimental results. A simple
exact expression for the quantum discord of these states in terms of the
maximum conditional purity is also derived.Comment: 16 pages, 5 figures, minor changes, to be published in J. Phys.
Optimized generation of spatial qudits by using a pure phase spatial light modulator
We present a method for preparing arbitrary pure states of spatial qudits,
namely, D-dimensional (D > 2) quantum systems carrying information in the
transverse momentum and position of single photons. For this purpose, a set of
D slits with complex transmission are displayed on a spatial light modulator
(SLM). In a recent work we have shown a method that requires a single
phase-only SLM to control independently the complex coefficients which define
the quantum state of dimension D. The amplitude information was codified by
introducing phase gratings inside each slit and the phase value of the complex
transmission was added to the phase gratings. After a spatial filtering process
we obtained in the image plane the desired qudit state. Although this method
has proven to be a good alternative to compact the previously reported
architectures, it presents some features that could be improved. In this paper
we present an alternative scheme to codify the required phase values that
minimizes the effects of temporal phase fluctuations associated to the SLM
where the codification is carried on. In this scheme the amplitudes are set by
appropriate phase gratings addressed at the SLM while the relative phases are
obtained by a lateral displacement of these phase gratings. We show that this
method improves the quality of the prepared state and provides very high
fidelities of preparation for any state. An additional advantage of this scheme
is that a complete 2\pi modulation is obtained by shifting the grating by one
period, and hence the encoding is not limited by the phase modulation range
achieved by the SLM. Numerical simulations, that take into account the phase
fluctuations, show high fidelities for thousands of qubit states covering the
whole Bloch sphere surface. Similar analysis are performed for qudits with D =
3 and D = 7.Comment: 12 pages, 7 figure
Scanning mechanism based on a programmable liquid crystal display
Includes bibliographical references (pages 112-113).In this work we propose a new robust optoelectronic scanning system for scanning microscopy. The device is based on a programmable liquid crystal television display (LCTV) that acts as a pixel-by-pixel controlled pure phase spatial light modulator. The computer addressed liquid crystal screen allows synthesize different diffractive optical elements at video rates. The phase shifts introduced by these elements make possible a complete control over the position and focusing of the scanning beam
Anamorphic zoom system based on liquid crystal displays
In this work we present an anamorphic zoom system, based on liquid crystal displays, which allows changing the magnification and distortion of an image very quickly, without mechanical parts and keeping the output plane stationary. The anamorphic lenses that make up the optical processor are obtained by displaying a combination of convergent-divergent cylindrical lenses, with arbitrary orientations, onto the spatial light modulators. In order to illustrate the capabilities of the system, some experimental results are show
Interferometry with few photons
Optical phase determination is an important and established tool in diverse
fields such as astronomy, biology, or quantum optics. There is increasing
interest in using a lower number of total photons. However, different noise
sources, such as electronic readout noise in the detector, and shot noise,
hamper the phase estimation in regimes of very low illumination. Here we report
a study on how the quality of phase determination is affected by these two
sources of noise. To that end, we experimentally reconstruct different
wavefronts by means of a point diffraction interferometer for different mean
intensities of illumination, up to . Our interferometer
features a Skipper-CCD sensor, which allows us to reduce the readout noise
arbitrarily, thus enabling us to separate the effect of these two sources of
noise. For two cases of interest: a spatial qudit encoding phase, consisting of
d = 6 uniform phase regions, and a more general continuous phase, we see that
reducing the readout noise leads to a clear improvement in the quality of
reconstruction. This can be explained by a simple noise model that allows us to
predict the expected fidelity of reconstruction and shows excellent agreement
with the measurements
Depth of focus increase by multiplexing programmable diffractive lenses
A combination of several diffractive lenses written onto a single programmable liquid crystal display (LCD) is proposed for increasing the Depth of Focus (DOF) of the imaging system as a whole. The lenses are spatially multiplexed in a random scheme onto the LCD. The axial irradiance distribution produced by each lens overlaps with the next one producing an extended focal depth. To compare the image quality of the multiplexed lenses, the Modulation Transfer Function (MTF) is calculated. Finally we obtain the experimental Point Spread Functions (PSF) for these multiplexed lenses and experimental results in which an extended object is illuminated under spatially incoherent monochromatic light. We compare the images obtained in the focal plane and in some defocused planes with the single lens and with three multiplexed lenses. The experimental results confirm that the multiplexed lenses produce a high increase in the depth of focus.Fil: Iemmi, Claudio Cesar. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campos, Juan. Universitat Autonoma de Barcelona; EspañaFil: Escalera, J. C.. Universitat Autonoma de Barcelona; EspañaFil: López Coronado, O. Universitat Autonoma de Barcelona; EspañaFil: Gimeno, R.. Universitat Autonoma de Barcelona; EspañaFil: Yzuel, María J.. Universitat Autonoma de Barcelona; Españ
Preparing arbitrary pure states of spatial qudits with a single phase-only spatial light modulator
We present a new method for preparing multidimensional spatial qudits by means of a single phase-only spatial light modulator (SLM). This method improves previous ones that use two SLMs, one working in amplitude regime and the other in phase regime. To that end, we addressed diffraction gratings on the slits that define the state and then we performed a spatial filtering in the Fourier plane. The amplitude of the coefficients of the quantum state are determined by the modulation deep of the diffraction gratings, and the relative phase is the mean phase value of the diffraction gratings. This encoding result to be more compact, less expensive and use the photons more efficiently.Instituto de Física La Plat
Preparing arbitrary pure states of spatial qudits with a single phase-only spatial light modulator
We present a new method for preparing multidimensional spatial qudits by means of a single phase-only spatial light modulator (SLM). This method improves previous ones that use two SLMs, one working in amplitude regime and the other in phase regime. To that end, we addressed diffraction gratings on the slits that define the state and then we performed a spatial filtering in the Fourier plane. The amplitude of the coefficients of the quantum state are determined by the modulation deep of the diffraction gratings, and the relative phase is the mean phase value of the diffraction gratings. This encoding result to be more compact, less expensive and use the photons more efficiently.Instituto de Física La Plat
‘I never realised everybody felt as happy as I do when I am around autistic people’: A thematic analysis of autistic adults’ relationships with autistic and neurotypical friends and family
AbstractMany autistic people are motivated to have friends, relationships and close family bonds, despite the clinical characterisation of autism as a condition negatively affecting social interaction. Many first-hand accounts of autistic people describe feelings of comfort and ease specifically with other autistic people. This qualitative research explored and contrasted autistic experiences of spending social time with neurotypical and autistic friends and family. In total, 12 autistic adults (10 females, aged 21–51) completed semi-structured interviews focused on time spent with friends and family; positive and negative aspects of time spent with neurotypical and autistic friends and family; and feelings during and after spending time together. Three themes were identified: cross-neurotype understanding, minority status and belonging. Investigation of these themes reveals the benefits of autistic people creating and maintaining social relationships with other autistic people, in a more systematic way than previous individual reports. They highlight the need for autistic-led social opportunities and indicate benefits of informal peer support for autistic adults.Lay abstractAlthough autistic people may struggle to interact with others, many autistic people have said they find interacting with other autistic people more comfortable. To find out whether this was a common experience, we did hour-long interviews with 12 autistic adults. We asked them questions about how it feels when spending time with their friends and family, and whether it felt different depending on whether the friends and family were autistic or neurotypical. We analysed the interviews and found three common themes in what our participants said. First, they found spending with other autistic people easier and more comfortable than spending time with neurotypical people, and felt they were better understood by other autistic people. Second, autistic people often felt they were in a social minority, and in order to spend time with neurotypical friends and family, they had to conform with what the neurotypical people wanted and were used to. Third, autistic people felt like they belonged with other autistic people and that they could be themselves around them. These findings show that having time with autistic friends and family can be very beneficial for autistic people and played an important role in a happy social life
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