Готові списки джерел за темами / Gradient echo memory

Добірка наукової літератури з теми "Gradient echo memory"

Автор: Grafiati

Опубліковано: 10 грудня 2022

Оновлено: 28 січня 2023

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Статті в журналах з теми "Gradient echo memory"

Higginbottom, D. B., J. Geng, G. T. Campbell, M. Hosseini, M. T. Cao, B. M. Sparkes, J. Bernu, N. P. Robins, P. K. Lam, and B. C. Buchler. "Dual-rail optical gradient echo memory." Optics Express 23, no. 19 (September 21, 2015): 24937. http://dx.doi.org/10.1364/oe.23.024937.

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BAI Hong-gui, 白洪贵, 黄震 HUANG Zhen, 王明峰 WANG Ming-feng, 王振兴 WANG Zhen-xing, and 郑亦庄 ZHENG Yi-zhuang. "Analysis of Polaritonic in the Quantum Gradient-echo Memory." Acta Sinica Quantum Optica 21, no. 3 (2015): 235–40. http://dx.doi.org/10.3788/asqo20152103.0235.

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Glorieux, Quentin, Jeremy B. Clark, Alberto M. Marino, Zhifan Zhou, and Paul D. Lett. "Temporally multiplexed storage of images in a gradient echo memory." Optics Express 20, no. 11 (May 16, 2012): 12350. http://dx.doi.org/10.1364/oe.20.012350.

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Carreño, F., and M. A. Antón. "Gradient echo memory in a tripod-like dense atomic medium." Optics Communications 283, no. 23 (December 2010): 4787–95. http://dx.doi.org/10.1016/j.optcom.2010.07.024.

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Carreño, F., and M. A. Antón. "Coherent control of light pulses stored in a Gradient Echo Memory." Optics Communications 284, no. 12 (June 2011): 3154–59. http://dx.doi.org/10.1016/j.optcom.2011.02.012.

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Sparkes, B. M., J. Bernu, M. Hosseini, J. Geng, Q. Glorieux, P. A. Altin, P. K. Lam, N. P. Robins, and B. C. Buchler. "Gradient echo memory in an ultra-high optical depth cold atomic ensemble." New Journal of Physics 15, no. 8 (August 23, 2013): 085027. http://dx.doi.org/10.1088/1367-2630/15/8/085027.

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Clark, Jeremy B., Quentin Glorieux, and Paul D. Lett. "Spatially addressable readout and erasure of an image in a gradient echo memory." New Journal of Physics 15, no. 3 (March 6, 2013): 035005. http://dx.doi.org/10.1088/1367-2630/15/3/035005.

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Zhang, Yan, Baoping Wang, Yang Fang, and Zuxun Song. "A Microwave Three-Dimensional Imaging Method Based on Optimal Wave Spectrum Reconstruction." Sensors 20, no. 24 (December 19, 2020): 7306. http://dx.doi.org/10.3390/s20247306.

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Анотація:

Limited by the Shannon–Nyquist sampling law, the number of antenna elements and echo signal data of the traditional microwave three-dimensional (3D) imaging system are extremely high. Compressed sensing imaging methods based on sparse representation of target scene can reduce the data sampling rate, but the dictionary matrix of these methods takes a lot of memory, and the imaging has poor quality for continuously distributed targets. For the above problems, a microwave 3D imaging method based on optimal wave spectrum reconstruction and optimization with target reflectance gradient is proposed in this paper. Based on the analysis of the spatial distribution characteristics of the target echo in the frequency domain, this method constructs an orthogonal projection reconstruction model for the wavefront to realize the optimal reconstruction of the target wave spectrum. Then, the inverse Fourier transform of the optimal target wave spectrum is optimized according to the law of the target reflectance gradient distribution. The proposed method has the advantages of less memory space and less computation time. What is more, the method has a better imaging quality for the continuously distributed target. The computer simulation experiment and microwave anechoic chamber measurement experiment verify the effectiveness of the proposed method.

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Pospisil, Karel, Monika Manychova, Josef Stryk, Marta Korenska, Radek Matula, and Vaclav Svoboda. "Diagnostics of Reinforcement Conditions in Concrete Structures by GPR, Impact-Echo Method and Metal Magnetic Memory Method." Remote Sensing 13, no. 5 (March 3, 2021): 952. http://dx.doi.org/10.3390/rs13050952.

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It is important to use adequately reliable non-destructive methods that would be capable of determining the reinforcement conditions in concrete structures. Three different methods: ground penetrating radar, impact-echo method, and metal magnetic memory method were used for testing laboratory-prepared reinforced concrete beams (with a reinforcing bar of the same diameter along its whole length, reinforcing bar locally impaired, and reinforcing bar interrupted). The ground-penetrating radar proved the correlation of signal parameters with the reinforcing bar condition. An impairment/interruption reinforcing bar appeared in the record from measurements in the transversal and longitudinal direction by changes of the observed depth of the reinforcing bar from the concrete surface and direct wave attenuation. The impact-echo method proved that the shifts of the dominant frequencies from the response signal correspond with the impairment/interruption of the reinforcing bar. Results of diagnostics by the metal magnetic memory method were presented by a magnetogram of the magnetic field strength and field gradient on the measured distance. The changes in the magnetic field strength proved different stress concentration zones due to the reinforcing bar condition. The used non-destructive methods showed that they are capable of indicating the different reinforcement conditions in reinforced concrete beams. This paper indicates in which cases and for what reason it is appropriate to use these three methods and in what way they differ from each other.

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Casey, B. J., Rolf J. Trainor, Jennifer L. Orendi, Anne B. Schubert, Leigh E. Nystrom, Jay N. Giedd, F. Xavier Castellanos, et al. "A Developmental Functional MRI Study of Prefrontal Activation during Performance of a Go-No-Go Task." Journal of Cognitive Neuroscience 9, no. 6 (November 1997): 835–47. http://dx.doi.org/10.1162/jocn.1997.9.6.835.

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This study examines important developmental differences in patterns of activation in the prefrontal cortex during performance of a Go-No-Go paradigm using functional magnetic resonance imaging (fMRI). Eighteen subjects (9 children and 9 adults) were scanned using gradient echo, echo planar imaging during performance of a response inhibition task. The results suggest four general findings. First, the location of activation in the prefrontal cortex was not different between children and adults, which is similar to our earlier pediatric fMRI results of prefrontal activation during a working memory task (Casey et al., 1995). Second, the volume of activation was significantly greater for children relative to adults. These differences in volume of activation were observed predominantly in the dorsal and lateral prefrontal cortices. Third, although inhibitory processes have typically been associated with more ventral or orbital frontal regions, the current study revealed activation that was distributed across both dorsolateral and orbitofrontal cortices. Finally, consistent with animal and human lesion studies, activity in orbital frontal and anterior cingulate cortices correlated with behavioral performance (i.e., number of false alarms). These results further demonstrate the utility of this methodology in studying pediatric populations.

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Більше джерел

Дисертації з теми "Gradient echo memory"

Hosseini, Mahdi. "Quantum optical storage and processing using raman gradient echo memory." Phd thesis, 2012. http://hdl.handle.net/1885/149882.

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The non-interacting and high-speed nature of light makes it an ideal carrier of information that is essential for transmission of quantum information. Indeed, many proposals and demonstrations of quantum cryptography rely on the use of fibre-optic networks. Construction of a memory that can store light and preserve its quantum properties will be useful in a range of quantum information systems such as secure quantum communication and quantum computation. This is why a quantum memory for light is a remarkable objective. The key to quantum memory is to store the probability amplitude of the possible outcomes of measurement but without measurement. An important criterion for a quantum memory is that the efficiency of the recall must exceed 50%. This is the crucial no-cloning limit for security of information, since it guarantees that nobody can access the information by copying it. This benchmark is important because any kind of deterministic amplification of quantum information is fundamentally impossible. On-demand retrieval of information and ability to controllably manipulate the quantum information are also important for quantum applications. When light is absorbed by atoms, it is actually possible to reverse the absorption process. In our memory system: light is absorbed by an ensemble of atoms and, using careful conditioning and control, we can cause the stored light to be regenerated and released at a later time. This is done by applying a gradient of magnetic field along the atomic ensemble that is the basis for our optical memory. To recall the light we flip the sign of the gradient field. This kind of reversible absorption is called photon echo, hence the name of our scheme: The Gradient Echo Memory (GEM). This simple protocol is used in our experiment and can be applied to a range of different atomic systems. We have extended the GEM protocol and experimentally implemented a memory using three-level atoms. We used an off-the-shelf Rb vapour cell operating above room temperature as the memory medium. In this realisation, we broke the efficiency record with 87% recall of the input light pulse. Moreover, through complete state tomography of coherent states we have demonstrated the ability of our memory to noiselessly store quantum states of light. We have also demonstrated that the memory can store a string of pulses and then recall the pulses ondemand in arbitrary order allowing re-sequencing of the stored information. Furthermore, we have shown that pulses could be time-compressed, time-stretched or split into multiple smaller pulses and selectively recalled in several pieces. This technique enables the construction of an optical random-access memory for quantum information. Moreover, the scheme to manipulate the spectral properties of optical data, stored inside the memory, has been introduced. We have also investigated the possibility of obtaining large nonlinear phase shifts between single photons inside the memory. Such strong interactions can be used for the implementation of universal quantum gates.

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Sparkes, Benjamin Michael. "Storage and manipulation of optical information using gradient echo memory in warm vapours and cold ensembles." Phd thesis, 2013. http://hdl.handle.net/1885/10578.

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Quantum memories for light lie at the heart of long-distance provably-secure communication [1], while containing the potential to help break current encryption methods [2], and allow better measurement of quantities than ever before [3]. Demand for a functioning quantum memory is therefore at a premium. Unfortunately, the same properties of light that make it such an effective carrier of quantum information make it difficult to store. Furthermore, by the laws of quantum mechanics, storage must be achieved without measurement to preserve the quantum state. A quantum memory needs to have an efficiency approaching unity without adding noise to the state, and storage times from milliseconds to seconds. Ideally it would also have a high bandwidth and be able to store many pieces of information simultaneously. Many different techniques are currently being developed and much experimental progress has been made over the past few years, with: efficiencies approaching 90% [4]; storage times of over seconds [5]; bandwidths of gigahertz [6, 7]; and over 1000 pieces of information stored at one time [8]. These results were, however, achieved using different memory schemes in different storage media. The challenge now is to reproduce these results with one memory. This thesis focuses on extending the gradient echo memory (GEM) scheme, which shows great promise due to the high efficiencies achieved (87%) [4]. GEM has also been used to demonstrate temporal compression and stretching of pulses, as well as a capacity to arbitrarily resequence stored information [9] and the interference of initially time-separated pulses [10]. Firstly, we demonstrate the noiseless nature of GEM storage in a warm vapour cell to prove that the output from the memory is the best-possible copy of the input allowed by quantum mechanics. We show GEM’s ability to coherently and precisely spectrallymanipulate stored information by having fine control over the memory’s frequency gradient, with potential applications for dynamic conditioning of information inside quantum networks [11]. We demonstrate cross-phase modulation of a stored light pulse with an additional optical field, a process with applications in quantum computing [12]. We also carry out storage of different spatial modes and arbitrary images, demonstrating the potential for orders of magnitude improvement in storage capacity. We then switch from warm vapour cells to cold atomic ensembles to improve the storage time of GEM, seeing a maximum coherence time of 350 μs (seven times that of the warm vapour system) and achieving efficiencies of up to 80%, on a par with the highest efficiency achieved with a cold atomic ensemble [13]. In the process we developed an ultra-dense cold atomic cloud with potential applications in a range of quantum optics experiments. Cold atoms, and the small volumes they occupy, also allowed us to develop an alternative to using magnetic field gradients for our alkali-atom memories in the form of a light-field gradient. This holds promise for extremely fast gradient switching and fine control over the gradient. We also present a digital locking code with application in a range of quantum optics experiments.

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Everett, Jesse Llewellyn. "Atom-light interfaces for quantum information processing." Phd thesis, 2018. http://hdl.handle.net/1885/147273.

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The emergence of quantum physics from the page to the lab and the world at large is an exciting development of recent years. The prospects of absolutely secure communication and efficient simulation of physical systems have spurred great human effort into understanding these possibilities and turning them into realities. Photons are the most easily manipulated quantum particles and are a promising candidate for implementing these technologies. Limitations of photons include the difficulty of keeping objects that move at the speed of light, and producing strong interactions between particles that do not normally interact. The work presented in this thesis is motivated by the possibility of overcoming these limitations. The ability to faithfully store and reproduce a quantum state is essential for many quantum information technologies. Quantum memories for light have been developed over the last two decades to provide this ability. The group at the Australian National University developed the gradient echo memory (GEM): A quantum state of light can be controllably stored and released from an atomic ensemble by the use of additional optical fields and magnetic field gradients. This scheme was previously shown to preserve the quantum characteristics of the light. We used the GEM scheme with a cold rubidium ensemble to create the first optical memory that simultaneously beat the no-cloning limit, a benchmark for many of the technologies relying on quantum memories, and the loss rate for a delay line composed of optical fibre. We also created an analogue to a pulsed optical resonator using GEM with a warm rubidium vapour. This was done by replacing the circulating optical field of a resonator with light stored in the memory, and replacing the coupling of light into and out of that circulating mode with storage and recall from the memory. The bandwidth and repetition rate of this resonator were rapidly tunable as they were controlled by external optical and magnetic fields. We worked on implementing GEM with strings of thousands of atoms strongly coupled to the evanescent field of an optical nanofibre. This raised new possibilities for creating a true random access memory that would allow a more flexible use of the multi-mode capacity of GEM. We developed the theory for a novel type of stationary light in the gradient echo memory. Our stationary light scheme relies on the destructive interference of counter-propagating optical fields throughout the memory. The optical intensity scales with optical depth, as with other forms of stationary light. However, as the destructive interference could be set up over a much greater distance, more of the optical depth is available for generating stationary light. Finally, we studied how a control-phase gate for single-photon optical states could be implemented using a nonlinear interaction with stationary light. The stationary light generated by one state modulates the phase of another state stored in the memory. The second state modifies the stationary light, also producing a back-action on the first state and generating the required cross-phase shift.

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Тези доповідей конференцій з теми "Gradient echo memory"

Buchler, B. C., M. Hosseini, G. Hétet, B. M. Sparkes, J. J. Longdell, M. J. Sellars, P. K. Lam, Timothy Ralph, and Ping Koy Lam. "High Efficiency Gradient Echo Memory with 3-Level Atoms." In QUANTUM COMMUNICATION, MEASUREMENT AND COMPUTING (QCMC): The Tenth International Conference. AIP, 2011. http://dx.doi.org/10.1063/1.3630216.

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Leung, Anthony, Aaron Tranter, Karun Paul, Jesse Everett, Pierre Vernaz-Gris, Daniel Higginbottom, Geoff Campbell, Ping Koy Lam, and Ben Buchler. "Extending gradient echo memory using machine learning and single photons." In Conference on Lasers and Electro-Optics/Pacific Rim. Washington, D.C.: OSA, 2018. http://dx.doi.org/10.1364/cleopr.2018.th1d.2.

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Longdell, J. J., G. Hétet, A. L. Alexander, P. K. Lam, and M. J. Sellars. "Gradient echo quantum memory for light using two-level atoms." In Optical Engineering + Applications, edited by Ronald E. Meyers, Yanhua Shih, and Keith S. Deacon. SPIE, 2007. http://dx.doi.org/10.1117/12.735471.

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Sparkes, B. M., M. Hosseini, G. Hétet, P. K. Lam, and B. C. Buchler. "Spectral Manipulation of Optical Pulses Using the Gradient Echo Memory Scheme." In International Quantum Electronics Conference. Washington, D.C.: OSA, 2011. http://dx.doi.org/10.1364/iqec.2011.i427.

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Lau, W. Y. Sarah, Anthony C. Leung, Karun V. Paul, Aaron D. Tranter, Geoff T. Campbell, Till J. Weinhold, Ping Koy Lam, Andrew G. White, and Ben C. Buchler. "Towards Storage of Sub-Megahertz Single Photons in Gradient Echo Memory." In 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). IEEE, 2019. http://dx.doi.org/10.1109/cleoe-eqec.2019.8872280.

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Sparkes, B. M., M. Hosseini, G. Hetet, P. K. Lam, and B. C. Buchler. "Spectral manipulation of optical pulses using the gradient echo memory scheme." In 2011 International Quantum Electronics Conference (IQEC) and Conference on Lasers and Electro-Optics (CLEO) Pacific Rim. IEEE, 2011. http://dx.doi.org/10.1109/iqec-cleo.2011.6193812.

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Gerasimov, K. I., S. A. Moiseev, V. I. Morozov, and R. B. Zaripov. "Spin frequency comb echo memory controlled by a pulsed-gradient of magnetic field." In Optical Technologies for Telecommunications 2014, edited by Vladimir A. Andreev, Vladimir A. Burdin, Albert H. Sultanov, and Oleg G. Morozov. SPIE, 2015. http://dx.doi.org/10.1117/12.2185472.

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Clark, J., Q. Glorieux, A. M. Marino, and P. D. Lett. "Coherent storage and retrieval of an image using a gradient echo memory in an atomic vapor." In Quantum Information and Measurement. Washington, D.C.: OSA, 2012. http://dx.doi.org/10.1364/qim.2012.qt1a.2.

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Glorieux, Q., J. Clark, A. M. Marino, and P. D. Lett. "Atomic diffusion effects on the coherent storage of an image using a gradient echo memory in a warm atomic vapor." In CLEO: Applications and Technology. Washington, D.C.: OSA, 2012. http://dx.doi.org/10.1364/cleo_at.2012.jth4k.2.

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