81 research outputs found
Quantum teleportation on a photonic chip
Quantum teleportation is a fundamental concept in quantum physics which now
finds important applications at the heart of quantum technology including
quantum relays, quantum repeaters and linear optics quantum computing (LOQC).
Photonic implementations have largely focussed on achieving long distance
teleportation due to its suitability for decoherence-free communication.
Teleportation also plays a vital role in the scalability of photonic quantum
computing, for which large linear optical networks will likely require an
integrated architecture. Here we report the first demonstration of quantum
teleportation in which all key parts - entanglement preparation, Bell-state
analysis and quantum state tomography - are performed on a reconfigurable
integrated photonic chip. We also show that a novel element-wise
characterisation method is critical to mitigate component errors, a key
technique which will become increasingly important as integrated circuits reach
higher complexities necessary for quantum enhanced operation.Comment: Originally submitted version - refer to online journal for accepted
manuscript; Nature Photonics (2014
Field-sensitive addressing and control of field-insensitive neutral-atom qubits
The establishment of a scalable scheme for quantum computing with addressable
and long-lived qubits would be a scientific watershed, harnessing the laws of
quantum physics to solve classically intractable problems. The design of many
proposed quantum computational platforms is driven by competing needs:
isolating the quantum system from the environment to prevent decoherence, and
easily and accurately controlling the system with external fields. For example,
neutral-atom optical-lattice architectures provide environmental isolation
through the use of states that are robust against fluctuating external fields,
yet external fields are essential for qubit addressing. Here we demonstrate the
selection of individual qubits with external fields, despite the fact that the
qubits are in field-insensitive superpositions. We use a spatially
inhomogeneous external field to map selected qubits to a different
field-insensitive superposition ("optical MRI"), minimally perturbing
unselected qubits, despite the fact that the addressing field is not spatially
localized. We show robust single-qubit rotations on neutral-atom qubits located
at selected lattice sites. This precise coherent control is an important step
forward for lattice-based neutral-atom quantum computation, and is quite
generally applicable to state transfer and qubit isolation in other
architectures using field-insensitive qubits.Comment: press embarg
Color afterimages in autistic adults
It has been suggested that attenuated adaptation to visual stimuli in autism is the result of atypical perceptual priors (e.g., Pellicano and Burr in Trends Cogn Sci 16(10):504â510, 2012. doi:10.â1016/âj.âtics.â2012.â08.â009). This study investigated adaptation to color in autistic adults, measuring both strength of afterimage and the influence of top-down knowledge. We found no difference in color afterimage strength between autistic and typical adults. Effects of top-down knowledge on afterimage intensity shown by Lupyan (Acta Psychol 161:117â130, 2015. doi:10.â1016/âj.âactpsy.â2015.â08.â006) were not replicated for either group. This study finds intact color adaptation in autistic adults. This is in contrast to findings of attenuated adaptation to faces and numerosity in autistic children. Future research should investigate the possibility of developmental differences in adaptation and further examine top-down effects on adaptation
A framework for the firstâperson internal sensation of visual perception in mammals and a comparable circuitry for olfactory perception in Drosophila
Perception is a first-person internal sensation induced within the nervous system at the time of arrival of sensory stimuli from objects in the environment. Lack of access to the first-person properties has limited viewing perception as an emergent property and it is currently being studied using third-person observed findings from various levels. One feasible approach to understand its mechanism is to build a hypothesis for the specific conditions and required circuit features of the nodal points where the mechanistic operation of perception take place for one type of sensation in one species and to verify it for the presence of comparable circuit properties for perceiving a different sensation in a different species. The present work explains visual perception in mammalian nervous system from a first-person frame of reference and provides explanations for the homogeneity of perception of visual stimuli above flicker fusion frequency, the perception of objects at locations different from their actual position, the smooth pursuit and saccadic eye movements, the perception of object borders, and perception of pressure phosphenes. Using results from temporal resolution studies and the known details of visual cortical circuitry, explanations are provided for (a) the perception of rapidly changing visual stimuli, (b) how the perception of objects occurs in the correct orientation even though, according to the third-person view, activity from the visual stimulus reaches the cortices in an inverted manner and (c) the functional significance of well-conserved columnar organization of the visual cortex. A comparable circuitry detected in a different nervous system in a remote species-the olfactory circuitry of the fruit fly Drosophila melanogaster-provides an opportunity to explore circuit functions using genetic manipulations, which, along with high-resolution microscopic techniques and lipid membrane interaction studies, will be able to verify the structure-function details of the presented mechanism of perception
A framework for the first-person internal sensation of visual perception in mammals and a comparable circuitry for olfactory perception in Drosophila
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