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How does the brain generate consciousness? The present paper is an attempt to answer this question from the perspective of the QBIT theory. In sum, the theory argues that the brain has a prior belief (P) about the stimulus that has caused a sensory representation (R) to be created in the brain. When the conditional entropy of P given R becomes less than zero, the brain becomes more than certain about (i.e. becomes conscious of) the stimulus. Conditional entropy can become negative (and thus the brain can become more than certain) only if the brain uses entangled quantum information in its computations. The QBIT theory suggests that, at the most fundamental level, consciousness is nothing but a special kind of entangled information. [ABSTRACT FROM AUTHOR]

In the field of cybersecurity, hackers often enter computer systems despite current security measures, owing to the huge amount of network traffic that makes intruder identification difficult. Differentiating between authorized traffic and abnormal data produced by Distributed Denial of Service (DDoS) attackers is still a major difficulty. This research provides a unique technique that uses Quantum Machine Learning (QML) to improve security protocols for secure communication between two parties. Our strategy enhances detection accuracy and speed by using the characteristics of quantum neural networks. The approach includes creating a dataset from network traffic patterns, preprocessing it, and then turning it into quantum bits via angle embedding. The research uses outlier analysis, min-entropy, and quantum state fidelity to distinguish between normal and abnormal data patterns. The dispersed randomness of network header data is measured using entropy, which aids in identifying security concerns. The suggested QML-based methodology outperforms conventional approaches and current models, including AMM-CNN and ANN models, with a detection accuracy of 99.87% for DDoS attacks. This advancement leads to more effective and secure communication networks. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride exhibits two types of defects with great potential for quantum information technologies: single-photon emitters (SPEs) and one-dimensional grain boundaries hosting topologically-protected phonons, termed as topologically-protected phonon lines (TPL). Here, by means of a simple effective model and density functional theory calculations, we show that it is possible to use these phonons for the transmission of information. Particularly, a single SPE can be used to induce single-, two- and qubit-phonon states in the one-dimensional channel, and (ii) two distant SPEs can be coupled by the TPL that acts as a waveguide, thus exhibiting strong quantum correlations. We highlight the possibilities offered by this material-built-in nano-architecture as a phononic device for quantum information technologies. [ABSTRACT FROM AUTHOR]

Material discovery is a phenomenon practiced since the evolution of the world. The discovery of materials has led to significant development in varied fields such as Science, Engineering and Technology. Computationally simulating molecules has been an area of interest in the industry as well as academia. However, simulating large molecules can be computationally expensive in terms of computing power and complexity. Quantum computing is a recent development that can improve the efficiency in predicting properties of atoms and molecules which will be useful for material design. The Variational Quantum Eigensolver (VQE) is one such quantum algorithm used to calculate the ground state energy of molecules or ions. In this study, we have done a comparative analysis of the parameters that constitute the VQE algorithm. This includes components such as basis, qubit mapping, ansatz, and optimizers used. We have also developed a database consisting of 79 single atoms and their variations of oxidation states and 33 molecules with the data of their Hamiltonian and ground state energy and dipole moment. [ABSTRACT FROM AUTHOR]

Shor's algorithm solves the elliptic curve discrete logarithm problem (ECDLP) in polynomial time. To optimize Shor's algorithm for binary elliptic curves, reducing the cost of binary field multiplication is essential because it is the most cost-critical arithmetic operation. In this paper, we propose Toffoli gate count-optimized, space-efficient (i.e., no ancilla qubits are used) quantum circuits for binary field ( (F 2 n) ) multiplication. To achieve this, we leverage the Karatsuba-like formulae and demonstrate that its application can be implemented without the need for ancillary qubits. We optimize these circuits in terms of CNOT gate count and depth. Building upon the Karatsuba-like formulae, we develop a space-efficient CRT-based multiplication technique utilizing two types of out-of-place multiplication algorithms to reduce the CNOT gate count. Our quantum circuits exhibit an extremely low Toffoli gate count of O (n 2 log 2 ∗ n) , where log 2 ∗ represents the iterative logarithmic function that grows very slowly. When compared to recent Karatsuba-based space-efficient quantum circuit, our approach requires only (10–25 %) of the Toffoli gate count and Toffoli depth for cryptographic field sizes in the range of n = 233–571. To the best of our knowledge, this represents the first successful utilization of the Karatsuba-like formulae and CRT-based multiplication in quantum circuits. [ABSTRACT FROM AUTHOR]

The resonant microwave pulses have been shown to be able to create magnetization of high-spin (S ≥ 1) metal ions even in the absence of an external magnetic field. This transformation of the ion spin states is similar to the "alignment–orientation" transition in atomic spectroscopy. These manipulations make it possible to translate the results of elementary quantum computing operations performed in zero magnetic fields into physically observable quantities. [ABSTRACT FROM AUTHOR]

Advances in quantum information processing can open a way for numerous applications of the processing in various fields of science and technology: communication, precision measurement, computing, nano-scale detectors, and sensors. Classical and various quantum correlations have been studied in real spin 1/2 systems. The nonlocality measures provide a novel classification scheme for bipartite states, highlighting that nonlocality is a quantum resource distinct from other types of quantum correlations. We first studied the temperature and field dependencies of nonlocality measure in the three fictitious spin 1/2 system, which represents a nuclear spin-7/2 placed in magnetic and inhomogeneous electric fields. The relationship between nonlocality and other quantum correlations (entanglement and geometric discord) was studied. The Hamiltonian and spin operators for a spin 7/2 are represented in the basis formed by the Kronecker products of the Pauli matrices. This transformation allows us to represent a spin 7/2 as a system of three coupled fictitious spins 1/2 and, from the quantum information point of view, as an equivalent system of three coupling qubits. Well-developed methods were used to calculate measures of quantum correlations. For example, we consider 59Co (spin 7/2) in the compounds [Co(NH3)5Cl]Cl2 and Ca3Co2O6. The interaction between the fictitious spins of 59Co nuclei depends on the magnitude and direction of the external magnetic field. Other potential cases of quantum correlations can be realized based on nuclear spins 7/2 in solid-state systems, for instance, such as 51V, 165Ho, or 123Sb. [ABSTRACT FROM AUTHOR]

We analyze in detail a procedure of entangling of two singlet–triplet (S– T 0 ) qubits operated in a regime when energy associated with the magnetic field gradient, Δ B z , is an order of magnitude smaller than the exchange energy, J, between singlet and triplet states (Shulman et al. in Science 336:202, 2012). We have studied theoretically a single S– T 0 qubit in free induction decay and spin echo experiments. We have obtained analytical expressions for the time dependence of components of its Bloch vector for quasistatic fluctuations of Δ B z and quasistatic or dynamical 1 / f β -type fluctuations of J. We have then considered the impact of fluctuations of these parameters on the efficiency of the entangling procedure which uses an Ising-type coupling between two S– T 0 qubits. In particular, we have obtained an analytical expression for evolution of two qubits affected by 1 / f β -type fluctuations of J. This expression indicates the maximal level of entanglement that can be generated by performing the entangling procedure. Our results deliver also an evidence that in the above-mentioned experiment S– T 0 qubits were affected by uncorrelated 1 / f β charge noises. [ABSTRACT FROM AUTHOR]

Landauer's bound is applicable to irreversible quantum operations. In this study, we showcased that the Doppler temperature manifests the existence of Landauer's bound, which does not block a spin from (irreversibly) flipping with a tiny amount of energy via quantum tunneling. Verified by a spin–spin magnetic interaction experiment, this (energy) amount was determined to be only 1.25 times the theoretical value of Landauer's bound. Based on Heisenberg's principle, we defined information from a measuring perspective: one bit of information corresponds to the smallest error when quantifying the product of the measured energy uncertainty ( Δ E ) and the measured time duration ( Δ t ). We then illustrate an optically manipulated, spin-encoded, near-Landauer-bound, near-Heisenberg-limit quantum computer that encompasses this new definition of information. This study may represent the last piece of the puzzle in understanding both quantum Landauer erasure and Heisenberg's quantum limit since a single spin is the smallest information carrier. [ABSTRACT FROM AUTHOR]

Qutrit is a three-level quantum system with a higher level than qubits, which can process quantum information in a more complex state space. Therefore, in some information processing tasks, qutrits are more efficient than qubits. In this paper, we first briefly review the basic knowledge of qubit and extend it to the qutrit scenario. Then, the noiseless qutrit channel is given by simple extension, and the transmission characteristics between it and the noiseless qubit channel are discussed. Subsequently, we provided a three-dimensional version of the amplitude damping channel based on its construction method. In this paper we will refer to it as the noisy qutrit channel N (ρ) . Finally, we discuss the transmission characteristics of N (ρ) and the amplitude damping channel, as well as the expected fidelity and entanglement fidelity of N (ρ) . What's interesting is that we find whether it is a noisy channel or a noiseless channel, the qutrit channel can send qubit information, but the qubit channel cannot send qutrit information completely. The special case in which the qubit channel can send qutrit information completely is when the input qutrit state is | 0 ⟩ or | 1 ⟩ or a linear combination of | 0 ⟩ and | 1 ⟩ . [ABSTRACT FROM AUTHOR]

The quantum mechanical transition probability is symmetric. A probabilistically motivated and more general quantum logical definition of the transition probability was introduced in two preceding papers without postulating its symmetry, but in all the examples considered there it remains symmetric. Here we present a class of binary models where the transition probability is not symmetric, using the extreme points of the unit interval in an order unit space as quantum logic. We show that their state spaces are strictly convex smooth compact convex sets and that each such set K gives rise to a quantum logic of this class with the state space K. The transition probabilities are symmetric iff K is the unit ball in a Hilbert space. In this case, the quantum logic becomes identical with the projection lattice in a spin factor which is a special type of formally real Jordan algebra. [ABSTRACT FROM AUTHOR]

Young developed a Neo-Piagetian/Neo-Eriksonian lifespan developmental model that consists of 25 substages in cognitive and socioaffective development. The model includes five stages X five cyclically recurring substages that develop with respect to both cognitive (Neo-Piagetian) and socioaffective (Neo-Eriksonian) development. Here, the model is elaborated by expanding the substage component from five steps to six, through adding a preliminary perception/ perturbation step. The six-step sequence is described according to three dimensions within which they can be situated, borrowing from qubit quantum theoric modeling. The transition mechanism related to substage transitions in the cognitive Neo-Piagetian portion of the model is described according to catalytic function, as developed in RAF network theory. The transition mechanism is also workable according to the qubit quantum theoric model. However, further conceptualization is needed to represent mathematically the revised model according to these two models. The paper also expands on the adult stage of Collective Intelligence. Network theory is given prominence to allow for testable predictions of the model. The overall theory is named Integrative Constructivist Relational Adaptation, and is referred to as a supra-theory. [ABSTRACT FROM AUTHOR]

Quantum control is a necessary tool for a variety of modern quantum technologies as it allows to optimally manipulate quantum systems for various tasks. Traps are points of local but not global optimum of the objective functional for a given quantum control problem. In a more general sense, traps are critical points of the objective functional which are hard to escape by local search algorithms. Here a review of some results of the analysis of possibility of having traps in landscapes of coherently controlled closed quantum systems is given. In one-qubit case, there are no traps. For special multilevel quantum systems, higher-order traps may appear. [ABSTRACT FROM AUTHOR]

The rapid development of quantum technology challenges the security of modern cryptography, which causes concern from the cryptographic community about the quantum implementation of cryptographic algorithms, as it is an important component of many quantum attacks. In this paper, the construction of quantum circuits for Camellia block cipher is investigated. Firstly, a 4-bit S-box is derived from the hardware circuit of the Camellia S-box, which divides the S-box circuit into three parts. Then, based on the rearranged circuit, as well as the implementation of the CCCNOT gate, the construction of the NCT-based circuit for the Camellia S-box is researched. Meanwhile, combined with the observations on the rearranged S-box circuit and the discussion on the in-place implementation of different matrices, a quantum circuit for the Camellia S-box with lower T-depth is presented. As an application, the various S-box circuits are used to construct quantum circuits for the Camellia family. The results reveal that the memory-efficient and depth-efficient quantum circuits of Camellia can be constructed with lower T-depth and T · M value. Besides, for each instance of Camellia, compared with existing state-of-the-art implementation with lowest T-depth and T · M value, the depth-efficient circuit designed in this work only costs about 35% of the qubits. [ABSTRACT FROM AUTHOR]

In this paper, we construct a simple qubit using impurity-center quantum dots with a spherical Gaussian confining potential and analyze the rationality and superiority of this kind of qubit. Based on the Pekar-type variational method, Gaussian entropy and ground-state lifetime expressions under an electromagnetic field environment are derived. The numerical results show that the variation of Gaussian entropy of the system with the change of the quantum dot confinement range presents an inverted asymmetric "Gaussian distribution", and the time evolution of the Gaussian entropy presents the characteristics of plane wave propagation. The oscillation amplitude of Gaussian entropy decreases with increasing the electric field intensity but increases with increasing the magnetic induction intensity. However, the oscillation period of Gaussian entropy increases with increasing the electric field intensity but decreases with increasing the magnetic induction intensity. The ground-state lifetime of the system increases with increasing the well depth of the confining potential and the dielectric constant ratio of the quantum dots but decreases with increasing the confining potential range and electron–phonon coupling constant, respectively. The ground-state lifetime decreases with increasing temperature and electric field intensity, respectively, but increases with increasing the magnetic induction intensity. The conclusions of this paper can provide a reference for constructing the qubit using semiconductor quantum dots, optimizing information storage and transmission, and suppressing decoherence. [ABSTRACT FROM AUTHOR]

In recent years, the quantum implementation of symmetric ciphers has received much attention. In this paper, we investigate the construction of quantum circuits based on different gate sets for the SM4 block cipher, which is the national standard of commercial cryptography of China and is standardized in ISO/IEC. First, we construct reversible circuits using Pauli-X gates, CNOT gates and Toffoli gates (i.e., the NCT gate set) for the SM4 S-box, based on which we design two circuits for the SM4 S-box with Clifford+T gates by applying the quantum And gate and existing decomposition scheme of the Toffoli gate, respectively. In addition, we propose a new in-place 1 implementation for the linear transformation in the SM4 round function. Finally, taking the qubit consumption and the T · M value (the product of qubit consumption and nonlinear gate depth of a quantum circuit) as metrics, we investigate the application of various circuits we designed to the construction of quantum circuits for SM4. The results show that we can always construct a subroutine/stand-alone circuit based on the NCT gate set, or based on Clifford+T gates for SM4 with fewer qubits or lower T · M value than existing state-of-the-art implementations. [ABSTRACT FROM AUTHOR]

Designing quantum arithmetic logic unit, quantum full adder and quantum full subtractor are the most vital digital circuits. The paper first presents the fundamentals of reversible quantum computing and quantum implementation design methodology with matrix modeling approach of realization of controlled gates. For any designer, it is challenging to reduce the controlled-gate count in circuit implementation. Based on the available 3 × 3 reversible quantum gates, the optimized quantum implementations of five novel and efficient controlled adders/subtractors are presented. Significant improvements in all the performance parameters have been achieved. Moreover, optimized quantum cost improvement of 20%, 16%, 9%, 10% and 31.25% has been obtained. The paper makes comparison of adder/subtractor circuits for efficient quantum realization. It has been deducted that our proposed designs are combined in nature and are more efficient than existing separate adder/subtractor and combined designs. [ABSTRACT FROM AUTHOR]

We present a principle to determine whether a matrix is unitary. Through this principle, we can exclude some zero entries distribution in unitary matrices. As a result, we can construct higher order unitary matrices with a given zero entries distribution. We apply our results to construct CP-equivalent gates. [ABSTRACT FROM AUTHOR]

We introduce the quantum-house effect, a non-local quantum phenomenon which goes against classical intuition. We show how the effect can be achieved with any bipartite quantum state where neither subsystem is in a pure state. Besides its theoretical description, the quantum-house effect is also demonstrated on SpinQ Gemini, a 2-qubit liquid-state NMR desktop quantum computer. [ABSTRACT FROM AUTHOR]

Quantum computing is a modern technology that uses the laws of quantum mechanics to tackle issues like irreversibility and power dissipation, which are beyond the scope of traditional computing paradigms. To exploit quantum physics in many application fields, circuit design using reversible gates is a crucial task. In this paper, quantum implementation of three-input/three-output (3 × 3) reversible gates is presented. The functional matrices of most of the gates are presented for the first time in this paper. In addition, the quantum implementation of URG, FRSG1, R and JTF1 gates, which find importance in various practical applications, is presented for the first time in this paper. The paper concludes with a comparison of the performance parameters of reversible gates for efficient quantum circuit realization. It is shown that each gate has additional advantages in valid perspectives. The paper thus provides a useful library of 3 × 3 reversible gates for the implementation of higher-order quantum circuit design. [ABSTRACT FROM AUTHOR]

Quantum key distribution(QKD) is one of the most significant areas in quantum information theory. For nearly four decades, substantial QKD schemes are developed. In early years, the security of QKD protocols is depend on switching different bases, namely based on non-orthogonal state encoding. The most famous example is the BB84 protocol. Later, other techniques were developed for orthogonal state encoding. Examples of such protocols include the GV protocol and order-rearrangement protocols. In this paper, we present two QKD protocols based on orthogonal state encoding. One of them does not need to employ order-rearrangement techniques while the other needs to. We provide analyses for them, demonstrating that they are highly efficient when considering consumptions of both qubits and classical bits. Furthermore, the employment of maximally entangled states could be less than previous ones and so the measurement efficiency could be increased. We also modify the protocols for implementing in noisy channels by applying the testing state method. [ABSTRACT FROM AUTHOR]

In the last two decades, a lot of research has been done for finding the best physical implementation of a quantum computer. Due to integrablity with classical computation hardware and versatility in creating qubits and quantum gates, silicon quantum dot-based systems are one of the most promising systems. In this paper, we have modelled a universal Clifford set of single qubit quantum gates based on silicon quantum dots framework by using the Lindblad master equation, where electron spin resonance (ESR) has been employed for manipulation of qubit states. State spin probability evolution of each of the gates has been reported in presence of dephasing effect. Moreover, the density matrix approach and quantum process tomography of each of the single qubit gates has been investigated. Furthermore, it has been shown that by increasing the ac magnetic field, we can obtain a high-fidelity NOT gate for a considerably wider range of static magnetic fields. This provides us with greater control by considering both ac magnetic field as well static magnetic field. [ABSTRACT FROM AUTHOR]

It is commonly recognized that Landauer's bound holds in (irreversible) quantum measurement. In this study, we overturned this common sense by extracting a single spin from a spin–spin magnetic interaction experiment to demonstrate that Landauer's bound can be broken quantitatively by a factor of 10 4 ∼ 10 10 via quantum spin tunneling. It is the quantum limit ( ħ / 2 ≈ 10 - 34 J · s ), rather than Landauer's bound, that governs the performance of a spin qubit. An optically-manipulated spin-encoded quantum computer is designed, in which energy bound well below k B T to erase a spin qubit at the expense of a long spin relaxation time is theoretically sensible and experimentally verified. This work may represent the last piece of the puzzle in quantum Landauer erasure in terms of a single spin being the smallest and the closest to the quantum limit. [ABSTRACT FROM AUTHOR]

The paper introduces mathematical encoding for subjective experience and meaning in natural cognition. The code is based on a quantum-theoretic qubit structure supplementing classical bit with circular dimension, functioning as a process-causal template for representation of contexts relative to the basis decision. The qubit state space is demarcated in categories of emotional experience of animals and humans. Features of the resulting spherical map align with major theoreties in cognitive and emotion science, modeling of natural language, and semiotics, suggesting several generalizations and improvements. The developed model bridges psychological, quantum-theoretic, and semiotic perspectives, allowing for an integrative account of subjectivity, agency, and meaning in living Nature. [ABSTRACT FROM AUTHOR]

We formulate the superposition principle of two states of qubit as a nonlinear addition rule of mean values of spin projections onto three perpendicular directions and obtain explicit expressions for the mean values determining the superposition states in terms of the mean values of two initial pure states of the qubit. [ABSTRACT FROM AUTHOR]

A method for analyzing network traffic based on quantum machine learning is presented. A method for network traffic encoding into quantum computer terms is developed. The experimental results show the superiority of the proposed approach over traditional machine learning methods for detecting network attacks. [ABSTRACT FROM AUTHOR]

We analyze in details the time-evolution of measurement-induced disturbance (MID) and local quantum uncertainty (LQU) in a qubit-qutrit system influenced by a collective dephasing pink or brown noise. We investigate the cases where each noise spectrum is generated by either a single two-states stochastic fluctuator, or a set of multiple ones. We further consider for our study, two non-equivalent classes of one-parameter qubit-qutrit initial states, namely the p-states and the x-states. We demonstrate that the initial state is particularly relevant for the future evolution of quantum correlations (QCs). In fact MID and LQU are less powerful against decoherence effects in x-states than in p-states, where we show the joint existence of time-invariant and freezing dynamics of QCs. In general, MID is always stronger than LQU, but we show that both measures can capture the same correlations (i.e. they are equal to each other) for carefully selected ranges of entanglement parameter in p-states. However, MID and LQU are more powerful in the system when subjected to brown noise than to pink noise no matter the initial state or the number of fluctuators generating the decoherent process. The relevance of separable states for the community is further reinforced by our results, as both QCs measures perfectly certify the existence of QCs without entanglement in ranges of separability for the selected input states. [ABSTRACT FROM AUTHOR]

The paper describes an algorithm for semantic representation of behavioral contexts relative to a dichotomic decision alternative. The contexts are represented as quantum qubit states in two-dimensional Hilbert space visualized as points on the Bloch sphere. The azimuthal coordinate of this sphere functions as a one-dimensional semantic space in which the contexts are accommodated according to their subjective relevance to the considered uncertainty. The contexts are processed in triples defined by knowledge of a subject about a binary situational factor. The obtained triads of context representations function as stable cognitive structure at the same time allowing a subject to model probabilistically-variative behavior. The developed algorithm illustrates an approach for quantitative subjectively-semantic modeling of behavior based on conceptual and mathematical apparatus of quantum theory. [ABSTRACT FROM AUTHOR]

Quantum teleportation protocols are widely employed for secure transfer of quantum states to away part. In this paper, we present a new scheme for teleporting a N-qubit entangled state via a ( N + 1 )-qubit cluster state as quantum channel. In this scheme, the sender (Alice) performs a von Neumann measurement on her basis and announces the result to the receiver (Bob), let him to recover the original state by affecting unitary operator on his state. Here, firstly, we present our general scheme for teleportation of a N-qubit entangled state by using a ( N + 1 )-qubit cluster state; then, the proposed scheme is examined by a simple example in which a 6-qubit entangled state is teleported by employing the proposed scheme. Finally, we analyze the efficiency of the scheme and indicate its advantages. [ABSTRACT FROM AUTHOR]

In this paper, we study the physical properties and decoherence of strong coupling magneto-bipolaron qubit in a quantum dot under the effect of an external electric field. The magneto-bipolaron energies of ground and first excited states are evaluated using the Pekar variational method. The decoherence time and entropy are also evaluated. All these calculations are intended to show firstly the effect of both the magnetic and the electric fields on the quasi-particles' properties in the quantum dot. Our results show that all studied quasi-particles properties in the quantum dot are closely influenced by magnetic and electric fields. The decoherence time increases with increasing of the electric field strength, and decreases with increasing of the magnetic field strength and the electron–phonon coupling constant. From our analysis, it is obvious to see that the application of electric field and magnetic field have opposite effects on the qubit. Comparing both fields, the electric field is advantageous for qubit survival and information storage, while the magnetic field is detrimental to qubit survival and information storage, respectively. The entropy increases with increasing of the electric field strength, and decreases with increasing of the magnetic field strength. We also observe that in the absence of magnetic and electric fields, the entropy varies very slightly with the increase of the confinement strength. We can deduce that, these external fields can help us to modulate the period of information transfer in the system, and hence can be used to control its coherence. [ABSTRACT FROM AUTHOR]

We consider error correction, based on the theory of non-commutative graphs, for a model of a qubit interacting with quantum oscillator. The dynamics of the composite system is governed by the Schrödinger equation which generates positive operator-valued measure (POVM) for the system dynamics. We construct a quantum channel generating the non-commutative graph as a linear envelope of the POVM. The idea is based on applying a generalized version of a quantum channel using the apparatus of von Neumann algebras. The results are analyzes for a non-commutative graph generated by a qubit interacting with quantum oscillator. For this model the quantum anticlique which determines the error correcting subspace has an explicit expression. [ABSTRACT FROM AUTHOR]

Selecting the double-parameter asymmetric Gaussian (AG) potential to describe the confinement effects of electrons in quantum dot (QD), the effect of dielectric constant, dispersion and polarization on the properties of the QD qubit is studied by LLP–Pekar transformation variation method. By discussing the oscillation period of the qubit with the AG potential, the mechanism of influence of the material parameters such as the dielectric constant ratio and the electron–phonon coupling (EPC) constant on qubit survival time and information storage is clarified. Based on the Fermi gold rule and the even-order approximation, the qubit decoherence with AG potential is studied. It is revealed that increasing the dielectric constant ratio, the dispersion or the EPC constant of materials is all ways to solve the qubit decoherence due to spontaneous emission of phonons. The theoretical basis for phase rotation control of qubit spheres is given by improving dispersion coefficient or dielectric constant ratio of materials. [ABSTRACT FROM AUTHOR]

The problem of Hadamard quantum coin measurement in trials, with an arbitrary number of repeated consecutive last states, is formulated in terms of Fibonacci sequences for duplicated states, Tribonacci numbers for triplicated states, and -Bonacci numbers for arbitrary -plicated states. The probability formulas for arbitrary positions of repeated states are derived in terms of the Lucas and Fibonacci numbers. For a generic qubit coin, the formulas are expressed by the Fibonacci and more general, -Bonacci polynomials in qubit probabilities. The generating function for probabilities, the Golden Ratio limit of these probabilities, and the Shannon entropy for corresponding states are determined. Using a generalized Born rule and the universality of the -qubit measurement gate, we formulate the problem in terms of generic -qubit states and construct projection operators in a Hilbert space, constrained on the Fibonacci tree of the states. The results are generalized to qutrit and qudit coins described by generalized Fibonacci- -Bonacci sequences. [ABSTRACT FROM AUTHOR]

We describe the interaction between the qubit and the electromagnetic field in a waveguide in accordance with the Lee model using the fact that photons in the waveguide are quanta of a massive scalar neutral field. We study the case where the energy of the excited state of the qubit is larger than the photon mass. We find the stationary state of the "qubit electromagnetic field " system. We describe the evolution of nonstationary states under initial conditions of the general form. We present results of numerical calculations under the initial conditions of two types: 1) the qubit is in the excited state, and there is no photon; 2) the qubit is in the ground state, and the photon is present. The study is related to the consistent quantum theory of the qubit control with the goal to force qubits to make transitions from one state to another. [ABSTRACT FROM AUTHOR]

Quantum phase estimation is a paradigmatic problem in quantum sensing and metrology. Here we show that adaptive methods based on classical machine learning algorithms can be used to enhance the precision of quantum phase estimation when noisy non-entangled qubits are used as sensors. We employ the Differential Evolution (DE) and Particle Swarm Optimization (PSO) algorithms to this task and we identify the optimal feedback policies which minimize the Holevo variance. We benchmark these schemes with respect to scenarios that include Gaussian and Random Telegraph fluctuations as well as reduced Ramsey-fringe visibility due to decoherence. We discuss their robustness against noise in connection with real experimental setups such as Mach–Zehnder interferometry with optical photons and Ramsey interferometry in trapped ions, superconducting qubits and nitrogen-vacancy (NV) centers in diamond. [ABSTRACT FROM AUTHOR]

We have presented extensive and nonextensive entropy of RbCl quantum well qubits (QWQ). To this end, we have considered an electron that is coupled to the LO-phonon in RbCl quantum well to determine the energy eigenvalues and eigenfunctions of the ground and first excited states of the system using the Pekar variational method. Here, we have used extensive and nonextensive entropies like Shannon and Tsallis to study decoherence of RbCl QWQ for different parameters. Our results show that the entropies have the oscillatory periodic evolution as a function of time due to the form of the confinement potential. According to the obtained results, we can see that the entropies oscillate under a sinusoidal envelope with enhancing the confinement parameters. These results may be very helpful in the transmission of information in the nanostructure. [ABSTRACT FROM AUTHOR]

We quantify the entanglement and its variations via generalized concurrence, Meyer–Wallach measure and its generalizations. Then we investigate the interactions between qubits on complete graphs, tree graphs, chain graphs and loop graphs with 3 to 8 qubits. It is observed that the amount of all entanglement measures in tree graph in the first group of considered graphs, are equal. The complete equivalent graph is equal and the entanglement measures for these graphs change altering the number of qubits. Furthermore, it can be seen that the entanglement measures are increased augmenting the number of qubits in the chain graph and loop graph. The entanglement of loop graphs is equal to or greater than the entanglement of chain graphs assuming the same number of qubits. Also there is a significant relation between entanglement, number of qubits, and interactions between qubits for the second group of considered graphs. As the number of interactions (presented by edges) increases between the qubits, the entanglements increase in these states. It is shown that the employed entanglement measures reveal the different values changing the number of qubits (vertices). [ABSTRACT FROM AUTHOR]

We investigate theoretically the properties of the coherence time of a symmetric semi-exponential quantum well qubit using the linear combination operator method for the first time. We derive the influences of quantum well barrier height and the range of an asymmetrical semi-exponential confinement potential (ASECP) on the vibration frequency, first excited-state (FES) energy, excitation energy and coherence time using unitary transformations and Fermi's Golden Rule. We find that the vibration frequency, FES energy and excitation energy are increasing functions of the barrier height, but are decreasing ones of the ASECP range; the coherence time, however, has totally opposite properties. Our results may be useful for the design and implementation of solid-state quantum computation. [ABSTRACT FROM AUTHOR]

Quantum computing is proving to be very beneficial for solving complex machine learning problems. Quantum computers are inherently excellent in handling and manipulating vectors and matrix operations. The ever increasing size of data has started creating bottlenecks for classical machine learning systems. Quantum computers are emerging as potential solutions to tackle big data related problems. This paper presents a quantum machine learning model based on quantum support vector machine (QSVM) algorithm to solve a classification problem. The quantum machine learning model is practically implemented on quantum simulators and real-time superconducting quantum processors. The performance of quantum machine learning model is computed in terms of processing speed and accuracy and compared against its classical counterpart. The breast cancer dataset is used for the classification problem. The results are indicative that quantum computers offer quantum speed-up. [ABSTRACT FROM AUTHOR]

The dynamics-from-permutations of classical Ising spins is generalized here for an arbitrarily long chain. This serves as an ontological model with discrete dynamics generated by pairwise exchange interactions defining the unitary update operator. The model incorporates a finite signal velocity and resembles in many aspects a discrete free field theory. We deduce the corresponding Hamiltonian operator and show that it generates an exact terminating Baker–Campbell–Hausdorff formula. Motivation for this study is provided by the Cellular Automaton Interpretation of Quantum Mechanics. We find that our ontological model, which is classical and deterministic, appears as if of quantum mechanical kind in an appropriate formal description. However, it is striking that (in principle arbitrarily) small deformations of the model turn it into a genuine quantum theory. This supports the view that quantum mechanics stems from an epistemic approach handling physical phenomena. [ABSTRACT FROM AUTHOR]

Paramagnetic ions having two electrons and spin S = 1 in zero magnetic field are proposed for new physical performance of elementary quantum computing operations by pulsed manipulations with electron spins. For this purpose, a new type of microwave pulses with variable phases and different polarizations are shown can be used. Such pulses are able to induce different transitions between ion spin states. Some of those transitions are described by operators similar to quantum computing operators. To describe the effects of such pulses on hig-spin ions, a new way to represent exponential operators as polynomials of the Pauli matrices is proposed. [ABSTRACT FROM AUTHOR]

Clustering algorithms are used to classify the unlabeled data into a number of categories with polynomial time complexity. Quantum clustering algorithms are developed to improve the performance and to achieve higher gain. In this work, we implement the quantum k-means clustering algorithm on field-programmable gate array (FPGA) by exploiting the implicit parallelism of the FPGA technology to achieve high speed among the software-implemented recent proposals. To do that, we establish a new method to measure the inner product between two qubits which is based on the correlation between the Euclidean distance and the inner product. We also optimize the quantum gates in terms of speed and removing the discretization error. Experimental results show a reduction in the running time by 500× as compared to the classical k-means algorithm for the A1 standard dataset. [ABSTRACT FROM AUTHOR]

Owing to the disadvantages of low communication efficiency, high measuring complexity and implementation difficulties in the existing quantum state sharing protocols, an efficient and simple three-party deterministic quantum state sharing protocol based on Bell states is proposed. During the procession of the protocol, only Bell-state measurements is used and the communication efficiency is improved obviously, hence, the proposed protocol is easily realized in physical experiment and its successful probabilities be all 100%. On the other hand, the protocol is generalized from three parties to multiple parties, and the feasibility of the scheme is illustrated by taking the four-party quantum state sharing as an example. [ABSTRACT FROM AUTHOR]

A novel quantum steganography scheme is investigated based on efficient embedding algorithm of modified exploiting modification direction in this paper, which embeds two 2 n × 2 n binary images (secret information) into a 2 n × 2 n color image (carrier image). To improve the security of the secret information and enhance the robustness of the proposed scheme, a 2 n × 2 n binary image (secret key) is generated according to the exclusive or operation of two secret images. The secret key acts as the control key of choosing two channels from the carrier image's three channels of R, G and B (i.e., R, G or R, B channels chose as the pixel-group) to hide the secret information. In addition, the effective quantum circuits for investigated quantum steganography scheme are illustrated to better understanding the procedure of embedding algorithm. The experiment results simulated on the classical computer with MATLAB environment, and the numerical analyses demonstrate that the presented algorithm has good performance on imperceptibility and security. [ABSTRACT FROM AUTHOR]

In this work, an electron which is strongly coupled to the strong electron–phonon (e–p) in RbCl quantum pseudodot qubit is considered. First, we employ the Pekar variational method and obtain the eigenenergies and eigenfunctions of the ground and the first excited states of the system. Then, we have employed three different entropies such as Tsallis, Landsberg–Vedral, and Escort for the system subjected to an applied electric field. In this regard, we have studied the effect of polaronic radius, electric field, e–p coupling strength, and non-extensive parameter. It is found that the entropies oscillate with passing time. The entropies increase with enhancing electric field, e–p coupling strength and decrease with polaronic radius. The results show that the missing information in the RbCl pseudodot qubit can be controlled by changing the system parameters. According to the results, it is deduced that the entropy is an important quantity to display the total storage or missing information in a qubit. [ABSTRACT FROM AUTHOR]

Coherent properties are critical to quantum communication. The coherent properties of qubits have been considered for a RbCl asymmetric Gaussian confinement potential quantum well (AQCPQW) qubit by the Pekar-type variational method (PTVM) and the Fermi Golden Rule. Then, we analytically derived the coherence time (CT) changes with the polaron radius, the height and range of the AGCPQW. On the bases of the present work's numerical results, the CT will increase with the decrease in the height of the AGCPQW and the polaron radius. The CT decreases firstly and then increases with the increase in the confinement potential's range, and when the confinement potential's range takes the appropriate value, the CT takes a minimum value. [ABSTRACT FROM AUTHOR]

In this work, an electron was considered which is coupled to the LO-phonon in RbCl quantum pseudo-dot. The Pekar variational method was used to calculate the eigenenergies and eigenfunctions of the ground and the first-excited states of the system. Two different entropies were considered, the Shannon and Laplace, to study decoherence of RbCl pseudodot qubit for different parameters. According to the obtained results, it is found that the entropy has the oscillatory periodic evolution as a function of the time due to the form of the confinement potential. It is also found that the entropies oscillate under a sinusoidal envelope with increasing the confinement parameters. [ABSTRACT FROM AUTHOR]

Quantum entanglement and its paradoxical properties are of paramount importance in quantum information theory. In recent years, there has been an increasing interest in the studies of high-dimensional quantum states and their impact on quantum communication as it can encode and process more data. Photonic entanglement is usually an evanescent property as it is destroyed easily by its interaction with an external environment. Electronic qubits are stable and can store information for a long time. However, qudit systems are more efficient, stable and allow noise robustness than qubit system. In this article, we investigate bipartite entanglement between doubly ionised molecular qudit and electronic qubit in the Auger emission process for N 2 molecule following the absorption of a single photon without observing spin-orbit interaction (SOI). In the absence of SOI, Russell–Saunders coupling (L-S coupling) is applicable. The entanglement properties are estimated on the basis of negativity of partial transpose of the density matrix for Auger ionisation. We find that the entanglement depends on the spins of the singly ionised excited states and doubly ionised states of the molecules as well as on the directions of spin quantisation and of ejection of Auger electrons. A significant effect on the variation of negativity due to the linear dichroism (LD) has also been observed. [ABSTRACT FROM AUTHOR]

Selecting the asymmetric Gaussian (AG) potential to describe the confinement of electron in a disk-shaped quantum dot (QD), the ground state and the first excited state energy and wave function of the system are derived by using the Lee -- Low -- Pines (LLP) Pekar transformation variational method, and the two-level structure required for a qubit is constructed. The influence of material parameters such as the dispersion coefficient, dielectric constant ratio and electron -- phonon coupling constant on the qubit properties of AG potential QD with the electromagnetic field are investigated. The results show that the electric field and magnetic field have opposite adjustment functions for the formation of qubit. The electric field is advantageous for the qubit survival and information storage, while magnetic field and electron -- phonon coupling are detrimental to the qubit survival and information storage, respectively. The decoherence time of the qubit increases with increasing magnetic field cyclotron frequency ‘from the turning point’. Applying an electric field, increasing the dielectric constant ratio, the dispersion coefficient and the electron -- phonon coupling constant of the materials are all beneficial to improve the coherence of the qubit. [ABSTRACT FROM AUTHOR]

We consider a qubit-qutrit system interacting each other through an isotropic Heisenberg Hamiltonian in a uniform magnetic field. An expression for the entanglement between the two parties as a function of both the anisotropy factor and the expansion coefficients is found. It is also calculated the uncertainty in the concurrence Δ C (measured as the standard deviation) as a function of the anisotropy factor. We make a strictly mathematical assumption that there exists a canonical conjugate variable (called π) to the concurrence C . Furthermore, we assume that such two variables satisfy (Robertson, Phys. Rev. 34, 163 1929) uncertainty relation of the form (Δ A) 2 (Δ B) 2 > | 1 2 〈 ψ | [ A , B ] | ψ 〉 | 2 . From such an inequality we impose bounds for the uncertainty of π for several values of the anisotropy factor. The above may help to open a novel vision about the properties of the concurrence between a qubit and a qutrit. [ABSTRACT FROM AUTHOR]