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Noise modeling of a photon echo memory

Jin Y. Choi

Published Dec 1, 1997• 0 citations
OpenAlex

Abstract

The photon echo memory is one of the most attractive optical memories in terms of memory capacity and access speed. Fundamentally, the storage capacity and access speed are limited by the inhomogeneous bandwidth of the material. In reality, however, the storage capacity and data rates are further limited by several kinds of imperfections in the memory process. One of the main limiting factors is the noise caused by several sources. In this dissertation we categorize these noise sources into three groups, time domain noise, frequency domain noise, and detection noise. For each noise group, we create models and characterize the noise properties. We then simulate each noise model in the computer and compare the results with the analytical results. Experimental results are also presented. Those experimental results yield insight into the photon echo memory system and its physical noise characteristics. The dissertation concludes with an interpretation of the noise modeling approach described and proposes fiiture directions for this research area.

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Noise modelling of a photon echo memory in the frequency domain

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Time-domain optical data storage using photon echoes has received increasing attention in recent years. A particularly attractive feature of a time domain memory is the ability to store many bits of information in a very small spot and thereby increase the data storage density. In time domain memory based on photon echoes, the Fourier transform of the input data is written into the inhomogeneous linewidth.

IEEE Lasers and Electro-Optics Society Annual Meeting (LEOS)•Dec 23, 2002•0 citations

Bit error rates for a photon echo memory

Jin Y. Choi, John F. Walkup, Thomas F. Krile +1 more

The noise characteristics of the photon echo memory have been investigated. The photon echo memory has the ability to store many bits of information in a diffraction-limited spot, thereby dramatically increasing the storage density. The temporal Fourier transform of the input data sequence is written into the inhomogeneous absorption profile of the recording medium. Data are encoded by means of temporal modulation onto the waveform of a finite duration data beam. Individual bits are not localized to a specific spectral channel; instead, they are stored throughout a region of spectral-addressing space, In order to store and recall the input data accurately, the Fourier transform of the input data sequence must be narrower than the inhomogeneous bandwidth. In the photon echo memory mechanism, there are several factors affecting the system bit error rate such as finite-width write/read pulses, echo efficiency, shot noise, thermal noise, etc. The accuracy of the echo output depends on those system factors. In this paper we formulate a simple model of the photon echo system, and by analyzing this model we derive the relationship between the characteristics of the echo output signal and several factors such as the bandwidth of the system, echo efficiency, atom excited state population fluctuations, shot noise, and thermal noise.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE•Nov 5, 1998•1 citation

Optical Memories and Processing in Time- and Frequency Domain

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Spectral hole burning and photon echoes are the techniques for frequency-selective optical memories, which have the potential to increase areal data storage density by a factor 10**7. They also have the capability to perform in-memory data processing. In this thesis, several materials and techniques for optical memories in the frequency- and time domain have been investigated. In the frequency domain, ways to increase the storage density and the working temperature were studied using photon-gated spectral hole burning materials of the metal-tetrabenzoporphyrin derivatives. A selection rule for the electron acceptors in the donor-acceptor electron transfer systems was deduced. By doping the material with two different donors a maximum inhomogeneous line width of more than 30 THz was achieved. A polarization holographic technique was established for the formation and detection of spectral holes. Our results indicate that this technique can provide a better signal-to-noise ratio than that achieved by a conventional holographic technique, in particular for samples of poor optical quality. In the time domain, magnetic field-induced and the intensity-induced dephasing processes were studied in Pr3+ doped in a YAlO3 crystal and a Y2SiO5 crystal, respectively. As a step along the route to make photon echo based optical processing possible, the amplification of photon echo signals by the use of a fiber amplifier (Pr3+-doped ZBLAN) was demonstrated. A gain of 45 was achieved. The erasure of stored data using photon echoes has also been investigated. A technique to diagnose the phase and frequency stability of a light source by the photon echo erasure process was proposed and illustrated. An approach to bit-selective data erasure, that is free from laser phase and frequency fluctuations, is also suggested. A concept for an arbitrary shape pulse generator based on photon echoes and hole-burning was experimentally and theoretically studied. Finally, a comparison between the properties and capabilities of spectral hole burning and photon echoes was made.

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The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatialpoint) permits terahertzread and write speeds for transitions with transition probabilities as low as 1000 s(-1).

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This dissertation is devoted to the development of quantum memories for light. Quantum memory is an important part of future long-distance quantum fiber networks and quantum processing. Quantum memory is required to be efficient, multimode, noise free, scalable, and should be able to provide long storage times for practical applications in quantum communications and beyond. Here I concentrate on solving particular problems of different quantum protocols and find ways for extending the performance of memories and adding new capabilities. I theoretically show that an array of whispering-gallery resonators is capable of being an efficient and noise-free optical memory with an adjustable storage time. The potential for on-chip realization at room temperature makes the scheme attractive for easy implementation. The effect of Raman scattering in echo memory was evaluated experimentally and theoretically. The noise performance of gradient echo memory in Λ configuration proves, that the developed theory is in a good agreement with an experiment. I proposed a mechanism for extending the bandwidth of impedance-matched memories via a white-light cavity effect. The introduced additional dispersion compensates a bandwidth decrease induced by the cavity and hence increases the spectral zone of impedance matching. Theoretically the scheme allows to increase the bandwidth of high efficient storage (>90%) several times without adding extra noise. Finally, I have proposed an architecture of quantum random-access memory for time-bin photons. The architecture consists from a memory unit and a strongly coupled three-level atom. Both of them are placed in their own cavities, which are coupled to each other. The protocol allows to achieve quantum addressing of quantum information stored in the memory with only a single control unit. This is useful for numerous tasks in quantum machine learning.

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Theoretical Modelling of Temporal Compression of Optical Pulses and Pulse Sequences Using Photon Echoes

Mikael Afzelius

In recent years possible applications of the photon echo process in optical processing, data storage systems, bit-rate conversion of optical pulses, time compression of optical pulses etc. have been investigated.Much of this research aim at replacing electrical components in the framework of today's information networks with components that are entirely based on optics.It is likely that we in the future will see more and more of the electrical components linked to a fibre network being replaced by all optical components, e.g.routers and bit-rate converters.The concept of temporal compression of optical pulses, which is the subject of this thesis, could be used to increase the transmission rate through optical fibres and thereby use the full capacity of today's fibres.It should also be mentioned that more basic components, e.g.XOR gates, are studied in this research field and these components could possibly be used in future concepts of a "light-computer".In this thesis a theoretical model of time compression of both single optical pulses and optical pulse sequences using photon echoes is presented.A full analytical treatment was done for gaussian shaped pulses as a first step of building a numerical model.An analytic approximate approach was also used for both square pulses and pulse sequences.A theoretical understanding of the duration, the intensity spectrum and peak intensity of the compressed signals was reached.It is shown that the intensity spectrum of a compressed pulse sequence containing N bits is completely analogous to the pattern observed in the well-known Fraunhofer diffraction experiment with N slits.A numerical model was built and used to evaluate how non-linearities and noise affect the degree of compression.In addition theoretical models were developed to explain the effects of non-linearities and noise and the hope is that these might be used as guidelines on how to design future experiments in order to achieve highest possible degree of compression.Some of the results presented in this thesis is compared with experimental data obtained in the research group during the time this work was going on.

Lund reports on atomic physics•Jan 1, 2000•2 citations
The photon echo memory is one of the most attractive optical memories in terms of memory capacity and access speed. Fundamentally, the storage capacity and access speed are limited by the inhomogeneous bandwidth of the material. In reality, however, the storage capacity and data rates are further limited by several kinds of imperfections in the memory process. One of the main limiting factors is the noise caused by several sources. In this dissertation we categorize these noise sources into three groups, time domain noise, frequency domain noise, and detection noise. For each noise group, we create models and characterize the noise properties. We then simulate each noise model in the computer and compare the results with the analytical results. Experimental results are also presented. Those experimental results yield insight into the photon echo memory system and its physical noise characteristics. The dissertation concludes with an interpretation of the noise modeling approach described and proposes fiiture directions for this research area.
The noise characteristics of the photon echo memory have been investigated. The photon echo memory has the ability to store many bits of information in a diffraction-limited spot, thereby dramatically increasing the storage density. The temporal Fourier transform of the input data sequence is written into the inhomogeneous absorption profile of the recording medium. Data are encoded by means of temporal modulation onto the waveform of a finite duration data beam. Individual bits are not localized to a specific spectral channel; instead, they are stored throughout a region of spectral-addressing space, In order to store and recall the input data accurately, the Fourier transform of the input data sequence must be narrower than the inhomogeneous bandwidth. In the photon echo memory mechanism, there are several factors affecting the system bit error rate such as finite-width write/read pulses, echo efficiency, shot noise, thermal noise, etc. The accuracy of the echo output depends on those system factors. In this paper we formulate a simple model of the photon echo system, and by analyzing this model we derive the relationship between the characteristics of the echo output signal and several factors such as the bandwidth of the system, echo efficiency, atom excited state population fluctuations, shot noise, and thermal noise.
Spectral hole burning and photon echoes are the techniques for frequency-selective optical memories, which have the potential to increase areal data storage density by a factor 10**7. They also have the capability to perform in-memory data processing. In this thesis, several materials and techniques for optical memories in the frequency- and time domain have been investigated. In the frequency domain, ways to increase the storage density and the working temperature were studied using photon-gated spectral hole burning materials of the metal-tetrabenzoporphyrin derivatives. A selection rule for the electron acceptors in the donor-acceptor electron transfer systems was deduced. By doping the material with two different donors a maximum inhomogeneous line width of more than 30 THz was achieved. A polarization holographic technique was established for the formation and detection of spectral holes. Our results indicate that this technique can provide a better signal-to-noise ratio than that achieved by a conventional holographic technique, in particular for samples of poor optical quality. In the time domain, magnetic field-induced and the intensity-induced dephasing processes were studied in Pr3+ doped in a YAlO3 crystal and a Y2SiO5 crystal, respectively. As a step along the route to make photon echo based optical processing possible, the amplification of photon echo signals by the use of a fiber amplifier (Pr3+-doped ZBLAN) was demonstrated. A gain of 45 was achieved. The erasure of stored data using photon echoes has also been investigated. A technique to diagnose the phase and frequency stability of a light source by the photon echo erasure process was proposed and illustrated. An approach to bit-selective data erasure, that is free from laser phase and frequency fluctuations, is also suggested. A concept for an arbitrary shape pulse generator based on photon echoes and hole-burning was experimentally and theoretically studied. Finally, a comparison between the properties and capabilities of spectral hole burning and photon echoes was made.
The first analysis to our knowledge of the optical data storage density of photon-echo storage is presented. Mainly considering signal-to-noise ratio performance, we calculate the obtainable storage density for data storage and processing using photon echoes to be approximately 100 times the theoretical limit for conventional optical data storage. This limit is similar to that theoretically calculated for data storage by use of persistent spectral hole burning. For storage times longer than the upper-state lifetime the highest densities can, however, be obtained only if all the excited atoms decay, or are transferred, to a different state than that from which they were originally excited. The analysis is restricted to samples with low optical density, and it also assumes that for every data sequence, writing is performed only once. It is therefore not directly applicable to accumulated photon echoes. A significant feature of photon-echo storage and processing is its speed; e.g., addressing 1 kbyte/(spatialpoint) permits terahertzread and write speeds for transitions with transition probabilities as low as 1000 s(-1).
This dissertation is devoted to the development of quantum memories for light. Quantum memory is an important part of future long-distance quantum fiber networks and quantum processing. Quantum memory is required to be efficient, multimode, noise free, scalable, and should be able to provide long storage times for practical applications in quantum communications and beyond. Here I concentrate on solving particular problems of different quantum protocols and find ways for extending the performance of memories and adding new capabilities. I theoretically show that an array of whispering-gallery resonators is capable of being an efficient and noise-free optical memory with an adjustable storage time. The potential for on-chip realization at room temperature makes the scheme attractive for easy implementation. The effect of Raman scattering in echo memory was evaluated experimentally and theoretically. The noise performance of gradient echo memory in Λ configuration proves, that the developed theory is in a good agreement with an experiment. I proposed a mechanism for extending the bandwidth of impedance-matched memories via a white-light cavity effect. The introduced additional dispersion compensates a bandwidth decrease induced by the cavity and hence increases the spectral zone of impedance matching. Theoretically the scheme allows to increase the bandwidth of high efficient storage (>90%) several times without adding extra noise. Finally, I have proposed an architecture of quantum random-access memory for time-bin photons. The architecture consists from a memory unit and a strongly coupled three-level atom. Both of them are placed in their own cavities, which are coupled to each other. The protocol allows to achieve quantum addressing of quantum information stored in the memory with only a single control unit. This is useful for numerous tasks in quantum machine learning.
In recent years possible applications of the photon echo process in optical processing, data storage systems, bit-rate conversion of optical pulses, time compression of optical pulses etc. have been investigated.Much of this research aim at replacing electrical components in the framework of today's information networks with components that are entirely based on optics.It is likely that we in the future will see more and more of the electrical components linked to a fibre network being replaced by all optical components, e.g.routers and bit-rate converters.The concept of temporal compression of optical pulses, which is the subject of this thesis, could be used to increase the transmission rate through optical fibres and thereby use the full capacity of today's fibres.It should also be mentioned that more basic components, e.g.XOR gates, are studied in this research field and these components could possibly be used in future concepts of a "light-computer".In this thesis a theoretical model of time compression of both single optical pulses and optical pulse sequences using photon echoes is presented.A full analytical treatment was done for gaussian shaped pulses as a first step of building a numerical model.An analytic approximate approach was also used for both square pulses and pulse sequences.A theoretical understanding of the duration, the intensity spectrum and peak intensity of the compressed signals was reached.It is shown that the intensity spectrum of a compressed pulse sequence containing N bits is completely analogous to the pattern observed in the well-known Fraunhofer diffraction experiment with N slits.A numerical model was built and used to evaluate how non-linearities and noise affect the degree of compression.In addition theoretical models were developed to explain the effects of non-linearities and noise and the hope is that these might be used as guidelines on how to design future experiments in order to achieve highest possible degree of compression.Some of the results presented in this thesis is compared with experimental data obtained in the research group during the time this work was going on.