Quantum channels with memory

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Quantum turbo decoding for quantum channels exhibiting memory

Quantum turbo decoding for quantum channels exhibiting memory

The quantum channel’s memory effect were first stud- ied in 2002 by Macchiavello and Palma [23] for classical information transmission over a depolarizing channel and it was demonstrated that for a certain correlation value, encoding the classical information into maximally entangled quantum states is capable of enhancing the channel capacity over the product quantum states encoding for two succes- sive channel uses. This work was then extended to quasi- classical depolarizing channels [24], to Pauli channels [25], to more than two successive uses of Pauli channels [26] and to superdense-coded qudit 1 Pauli channels [27]. A model and a unitary representation of quantum channels with memory for classical and quantum information was introduced by Bowen and Mancini [28]. In 2005, a unified framework for quantum channels exhibiting memory was developed by Kretschmann and Werner [17], where the upper bounds of classical and of quantum channel capacities were derived for various scenarios, depending on whether the transmitter, the receiver or the eavesdropper has the control on the initial and final memory states. Most of the theoretical contributions on discrete quantum channels with memory assume contam- ination by Markovian correlated noise, since the properties of typical sequences generated by a Markov process are well understood [23]–[35].
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Many-body physics and the capacity of quantum channels with memory

Many-body physics and the capacity of quantum channels with memory

Despite these interesting observations, it is still an open question whether the sharp kinks in the capacity of these models still persist if the full correlated channel { E n } is considered as n → ∞ , or whether this behaviour is just an artefact of the truncation of the channel at low n. The main difficulty in deciding such questions is that even under the assumption that equations such as (6) (or its analogue for classical information—the regularized Holevo bound) represent the true quantum capacity of a given correlated channel { E n } , in most cases such variational expressions are extremely difficult to compute. It is, however, interesting to note that the non-analytic behaviour observed in the channel capacity of correlated channels is somewhat reminiscent of the non-analyticity of physical observables that define a (quantum) phase transition in strongly interacting (quantum) many-body systems, where in contrast true phase transitions usually only occur in the n → ∞ limit.
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Selfcomplementary quantum channels

Selfcomplementary quantum channels

A global unitary transformation considered in Eq. (25) that provides a coupling of a qubit system with a qubit environment can represent a selfcomplementary dynamics, if we assume that the phase changes linearly with time, θ = ωt. In such a dynamics, information oscillates between the system and the environment and the evolution depends on the history. Fig. 1 provides an illustration of this process. The successive images of the Bloch spheres represent now the successive moments of time. In panel c), the Bloch ball is contracted to a line segment. Then the points diverge to form a three-dimensional set again. This evolution clearly depends on both the present state and the previous history. This type of memory- based processes is called non-Markovian. In contrast, the so–called Markovian dynamics depends only on the present state of the quantum system.
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Continuous variable quantum digital signatures over insecure channels

Continuous variable quantum digital signatures over insecure channels

Digital signatures ensure the integrity of a classical message and the authenticity of its sender. Despite their far-reaching use in modern communication, currently used signature schemes rely on computational assumptions and will be rendered insecure by a quantum computer. We present a quantum digital signatures (QDS) scheme whose security is instead based on the impossibility of perfectly and deterministically distinguishing between quantum states. Our continuous-variable (CV) scheme relies on phase measurement of a distributed alphabet of coherent states and allows for secure message authentication against a quantum adversary performing collective beamsplitter and entangling-cloner attacks. Crucially, in the CV setting we allow for an eavesdropper on the quantum channels and yet retain shorter signature lengths than previous protocols with no eavesdropper. This opens up the possibility to implement CV QDS alongside existing CV quantum key distribution platforms with minimal modification.
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PRO-74 100-Channel VHF/UHF/Air/800 MHz Race Scanner

PRO-74 100-Channel VHF/UHF/Air/800 MHz Race Scanner

For example, if you want to listen to communications between the driv- er of car number 24 and that driver’s pit crew, find all the frequencies used by the driver’s team by using the steps in “Searching the Service Banks” on Page 25, using the supplied frequency guide, “Searching from a Selected Frequency” on Page 26, or using frequencies you al- ready know, then store a car number and the frequencies associated with that car number in the scanner’s channels. Then, you can display the car number as you scan those frequencies by using the information in “Scanning by Car Number” on Page 33.
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1key followed by the45 key

1key followed by the45 key

DO NOT USE THIS KEY SEQUENCE UNLESS ABSOLUTELY NECESSARY. A FULL MICROPROCESSOR reset is accomplished by holding both the [CLR] and [ENT] keys while switching On the unit using the [PWR] key. All memory channels, search banks, pass channels etc will be lost and blank. As a result the search and scan facilities will not operate until new data has been entered. Note: It is quite normal for the set to take about 30 seconds to recover from a FULL reset as all data is being deleted !!! Often there is no external indication that a reset is in progress so be patient, following a FULL reset the receiver will power On and the display will show 80 MHz.
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Lossless quantum prefix compression for communication channels that are always open

Lossless quantum prefix compression for communication channels that are always open

Koashi and Imoto 关 6 兴 argued that it is impossible to faith- fully encode a mixture of nonorthogonal quantum states if the particular output states of the quantum information source are not known. They modeled lossless data compres- sion as taking place in a register of N qubits. A compressed state in the register would be an unknown indeterminate- length quantum string with base length L, in which case only the remaining N− L qubits would be usable by other applica- tions without disturbing the compressed state. However, the base length L is not an observable; thus, the other applica- tions cannot determine how many qubits are available. Thus the remaining N− L qubits are not available for other appli- cations to use, unless there is some a priori knowledge about L for some reason.
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Density-matrix simulation of small surface codes under current and projected experimental noise

Density-matrix simulation of small surface codes under current and projected experimental noise

Although we have attempted to be thorough in the detailing of the circuit, we have neglected certain effects. We have used a simple model for C-Z gate errors as we lack data from experimental tomography (e.g., one obtained from two-qubit gate-set tomography 30 ). Most importantly, we have neglected leakage, where a transmon is excited out of the two lowest energy states, i.e., out of the computational subspace. Previous experi- ments have reduced the leakage probability per C-Z gate to ~0.3%, 31 and per single-qubit gate to ~0.001%. 32 Schemes have also been developed to reduce the accumulation of leakage. 33 Extending quantumsim to include and investigate leakage is a next target. However, the representation of the additional quantum state can increase the simulation effort significantly [by a factor of (9/4) 10 ≈ 3000]. To still achieve this goal, some further approximations or modi fi cations to the simulation will be necessary. Future simulations will also investigate the effect of
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Testing a quantum heat pump with a two level spin

Testing a quantum heat pump with a two level spin

in general, for any quantum heat pump with a single open decay channel per heat bath. We shall refer to all of these as endoreversible models, since their only source of irreversibility is the mismatch between “internal” and “external” temperatures [2]. On the other hand, models with various open decay channels per heat bath, such as the four-level heat pump of Figure 1b, are made up of detuned elementary stages. This gives rise to two distinct irreversible processes: internal dissipation and heat leaks [42], which keep energy transformation from being reversible. We refer to this type of system as irreversible heat pumps.
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Resonance fluorescence from an atomic quantum memory compatible single photon source based on GaAs droplet quantum dots

Resonance fluorescence from an atomic quantum memory compatible single photon source based on GaAs droplet quantum dots

The Schottky diode geometry used in our study enables us to charge tune the emission and spectrally fine tune the emission line of quantized energy levels of the QDs 27 . We observed resonance fluorescence in both contacted and non-electrically-contacted geometry, and about 50 % of the investigated QDs showed resonance fluores- cence. We note that in contrast to investigations on high quality InGaAs quantum dots in high quality micropillar cavities, 11,36 the application of additional weak 532 nm laser light on the investigated GaAs/AlGaAs turned out to improve the QD properties similar to other studies, for instance, Gazzano et al. 35 The measured linewidths
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Implementing Broadcast Channels with Memory for Electronic Voting Systems

Implementing Broadcast Channels with Memory for Electronic Voting Systems

In a real-world implementation of a given cryptographic protocol, the theoretical model of a BCM can at best be approximated. A common approach is to substitute the broadcast channel with memory by one or multiple additional parties participating in the protocol. These parties provide the service of accepting and memorizing the messages transmitted over the broadcast channel during the protocol execution. The service offered by such parties is what we call a bulletin board. It guarantees that messages cannot be deleted or modified, and it keeps track of the order in which the messages appeared. A bulletin board offering these two basic properties—called append-only bulletin board—is a prerequisite in almost every cryptographic voting protocol. In addition, some protocols require designated board sections for all involved parties (Cramer, Gennaro, and Schoenmakers 1997b), while other protocols require that the board rejects messages that are not well-formed (Haenni and Koenig 2013). When implementing a BB, appropriate solutions for such protocol-specific requirements need to be provided in addition to the append-only property (Hauser and Haenni 2016).
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Three-Reggeon cuts in QCD amplitudes

Three-Reggeon cuts in QCD amplitudes

One of remarkable properties of QCD is the Reggeization of all elementary particles in per- turbation theory, which is very important for theoretical description of high energy processes. The gluon Reggeization is especially important because it determines the high energy behaviour of non-decreasing with energy cross sections. In particular, it appears to be the basis of the BFKL (Balitskii-Fadin-Kuraev-Lipatov) equation, which was first derived in non- Abelian theories with spontaneously broken symmetry [1–3] and whose applicability in QCD was then shown [4]. The the amplitudes with gluon quantum numbers in cross-channels are dominant (have the largest ln s degrees) in each order of perturbation theory, they determine the s-channel discontinuities of amplitudes with the same and all other possible quantum numbers. It is extremely important that both in the leading logarithmic approximation (LLA) [5] and in the next-to-leading one (NLLA) (see [6], [7] and references therein) the amplitudes used in the unitarity relations are determined by the Regge pole contributions and have a simple factorized form (pole Regge form). Due to this, the Reggeization provides a simple derivation of the BFKL equation in the LLA and in the NLLA. The However, the Regge pole contributions are not sufficient in the NNLLA.
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A00 ” for the first channel location in memory bank “ A” and “A49 ” for the last memory

A00 ” for the first channel location in memory bank “ A” and “A49 ” for the last memory

The scan FREE time parameter determines how long the AR8200 will remain on an active frequency before resuming scan even though the frequency is still active. This is useful if you wish to gain a snap shot of activity without the AR8200 being tied to a busy frequency for long periods of time (such as when monitoring active amateur band repeaters etc). Scan FREE time saves you having to manually intervene to force the scan process to resume and saves the need to lockout memory channels using the channel PASS facility. The limits are OFF and 01 to 60 seconds (default OFF).

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Converse bounds for quantum and private communication over Holevo-Werner channels

Converse bounds for quantum and private communication over Holevo-Werner channels

Werner states have a host of interesting properties, which often serve to illuminate the unusual properties of quantum information. Starting from these states, one may define a family of quantum channels, known as the Holevo-Werner channels, which themselves afford several unusual properties. In this paper we use the teleportation covariance of these channels to upper bound their two-way assisted quantum and secret-key capacities. This bound may be expressed in terms of relative en- tropy distances, such as the relative entropy of entanglement, and also in terms of the squashed entanglement. Most interestingly, we show that the relative entropy bounds are strictly subadditive for a sub-class of the Holevo-Werner channels, so that their regularisation provides a tighter per- formance. These information-theoretic results are first found for point-to-point communication and then extended to repeater chains and quantum networks, under different types of routing strategies.
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Behaviour of Quantum Correlations and Violation of Bell Inequalities in some Noisy Channels

Behaviour of Quantum Correlations and Violation of Bell Inequalities in some Noisy Channels

Abstract: Quantum Correlations are studied extensively in quantum information domain. Entanglement Measures and Quantum Discord are good examples of these actively studied correlations. Detection of violation in Bell inequalities is also a widely active area in quantum information theory world. In this work, we revisit the problem of analyzing the behavior of quantum correlations and violation of Bell inequalities in noisy channels. We extend the problem defined in a recent study by observing the changes in negativity measure, quantum discord and a modified version of Horodecki measure for violation of Bell inequalities under amplitude damping, phase damping and depolarizing channels. We report different interesting results for each of these correlations and measures. All these correlations and measures decrease under decoherence channels, but some changes are very dramatical comparing to others. We investigate also separability conditions of example studied states.
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Generation and storage of optical entanglement in a solid state spin-wave quantum memory

Generation and storage of optical entanglement in a solid state spin-wave quantum memory

Photons have the advantage that they are extremely isolated from the environment, minimising the disruption of the quantum information they carry. They can also be used as ‘flying qubits’ in the transportation of quantum information between processors. Single photons also have uses outside of quantum information processing. For ex- ample, they can be used in the production of truly random numbers [25]. This is significant because it is very difficult to generate random numbers. Most protocols are only pseudo-random, with the numbers generated using complex numerical algorithms, which are still fundamentally deterministic. Many applications, such as cryptography, computer simulation, statistical sampling and modelling require a high degree of ran- domness and, given enough time, the sequence from a pseudo-random number generator will repeat itself. Single photons offer a solution because quantum noise is inherently random. Single photons hitting a 50:50 beam splitter have an equal probability of being transmitted or reflected. Their output direction provides a truly random source of ones and zeroes based on the intrinsic randomness of the quantum nature of light.
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Microcontroller Based Automatic Multichannel Temperature Monitoring System

Microcontroller Based Automatic Multichannel Temperature Monitoring System

The PIC18F4620 microcontroller uses 4 pins to interface with the PIC18F2620 microcontroller [7] where the slave select pin of PIC18F2620 microcontroller is connected to chip select pin of the PIC18F4620 microcontroller. SDI from the PIC18F4620 microcontroller is connected to the output data pin, SDO of the PIC16F2620 microcontroller and vice versa. The UART module [4] is used to transfer the data between PIC18F2620 and PIC16F876A microcontrollers. The transmit pin, TX of PIC18F2620 microcontroller is connected to the receive pin, RX of the PIC16F876A microcontroller and vice versa. The present date and time is sent from PIC16F876A to PIC18F2620 microcontrollers to be written into memory card every time the logging interval reached. PIC18F2620 microcontroller is Programmed using mikroC Compiler [11] in mikroC IDE environment into .hex format. The serial clock pin, SCK of both microcontrollers is connected together. It transfers the selected channels, the preset limit, mobile number, and current temperature reading from PIC18F4620 to PIC18F2620 microcontrollers to be logged into the memory card and the system restart. The hardware implementation of three microcontroller has been shown in figure IIIA.
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Quantized Three-Ion-Channel Neuron Model for Neural Action Potentials

Quantized Three-Ion-Channel Neuron Model for Neural Action Potentials

The Hodgkin-Huxley model describes the conduction of the nervous impulse through the axon, whose membrane’s elec- tric response can be described employing multiple connected electric circuits con- taining capacitors, voltage sources, and conductances. These conductances de- pend on previous depolarizing membrane voltages, which can be identified with a memory resistive element called memris- tor. Inspired by the recent quantization of the memristor, a simplified Hodgkin- Huxley model including a single ion chan- nel has been studied in the quantum regime. Here, we study the quantization of the complete Hodgkin-Huxley model, ac- counting for all three ion channels, and in- troduce a quantum source, together with an output waveguide as the connection to a subsequent neuron. Our system consists of two memristors and one resistor, describ- ing potassium, sodium, and chloride ion channel conductances, respectively, and a capacitor to account for the axon’s mem- brane capacitance. We study the behav- ior of both ion channel conductivities and the circuit voltage, and we compare the re- sults with those of the single channel, for a given quantum state of the source. It is remarkable that, in opposition to the single-channel model, we are able to re- produce the voltage spike in an adiabatic regime. Arguing that the circuit voltage is a quantum variable, we find a purely quantum-mechanical contribution in the system voltage’s second moment. This work represents a complete study of the Hodgkin-Huxley model in the quantum
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Quantum Set Intersection and its Application to Associative Memory

Quantum Set Intersection and its Application to Associative Memory

A Bound on Memory Size due to Pattern Completion. The bound on memory size that ensures a high probability of correct completion depends on the definition of the pattern completion procedure. If one defines pattern completion as the process of outputting any of a number of possible memory patterns when given a partial input, then the capacity bound of our memory is the amplification bound given in Equation 16. However, this is not always the case. Pattern completion capacity is usually defined as the maximal size of a random uniformly distributed memory set that, given a partial version x ′ of a memory x c ∈ M with d missing bits, outputs x c . The following theorem gives
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88A00026A A GA1830 Industrial Supervisory System Reference Manual May69 pdf

88A00026A A GA1830 Industrial Supervisory System Reference Manual May69 pdf

The addition of direct memory data channels to the basic I/O system provides the capability for transferring blocks of 16-bit words, one word at a time directly between memory and extern[r]

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