IET Quantum Communication最新文献

The Kolmogorov complexity of a string is the minimum length of a programme that can produce that string. Information distance between two strings based on Kolmogorov complexity is defined as the minimum length of a programme that can transform either string into the other one, both ways. The second quantised Kolmogorov complexity of a quantum state is the minimum average length of a quantum programme that can reproduce that state. In this paper, a second quantised information distance is defined based on the second quantised Kolmogorov complexity. It is described as the minimum average length of a transformation quantum programme between two quantum states. This distance's basic properties are discussed. A practical analogue of quantum information distance is also developed based on quantum data compression.

In this paper, a modified formulation of generalised probabilistic theories that will always give rise to the structure of Hilbert space of quantum mechanics, in any finite outcome space, is presented and the guidelines to how to extend this work to infinite dimensional Hilbert spaces are given. Moreover, this new formulation which will be called as extended operational-probabilistic theories, applies not only to quantum systems, but also equally well to classical systems, without violating Bell's theorem, and at the same time solves the measurement problem. A new answer to the question of why our universe is quantum mechanical rather than classical will be presented. Besides, this extended probability theory shows that it is non-determinacy, or to be more precise, the non-deterministic description of the universe, that makes the laws of physics the way they are. In addition, this paper shows that there is still a possibility that there might be a deterministic level from which our universe emerges, which if understood correctly, may open the door wide to applications in areas such as quantum computing. In addition, this paper explains the deep reason why complex Hilbert spaces in quantum mechanics are needed.

Medical imaging is considered one of the most important areas within scientific imaging due to the rapid and ongoing development in computer-aided medical image visualisation, advances in analysis approaches, and computer-aided diagnosis. Here, the principles of quantum computation and information to develop the field of medical image processing will be reviewed. The advancement of quantum computation in image processing has proved its outstanding properties for processing and storage capacity compared to the classical methods. This review provides a comprehensive summary of the common advanced approaches, methodologies and advanced applications in medical images based on quantum computation.

Quantum communication is an integral part of quantum computing, where teleportation of a quantum state has gained significant attention from researchers. Many teleportation schemes have been introduced in the recent past. In this study, the authors compare the teleportation of a single-qubit message among different entangled channels such as the two-qubit Bell channel, three-qubit GHZ channel, two/three-qubit cluster states, a highly entangled five-qubit state (Brown et al.) and the six-qubit state (Borras et al.). The authors calculate and compare the quantum costs for these channels. The authors also study the effects of six noise models: bit-flip noise, phase-flip noise, bit-phase-flip noise, amplitude damping, phase damping and depolarising error. These noise models may affect the communication channel used for teleportation. An investigation of the variation of the initial state's fidelity is performed for the teleported state in the presence of the noise model. It is observed that the fidelity decreases in all the entangled channels as the noise parameter η increases in the range [0, 0.5] for all the noise models. The fidelity shows an upward trend in the Bell, GHZ and three-qubit cluster state channels, as η varies in the range [0.5, 1.0] for all the noise models. However, in the rest of the three channels, the fidelity substantially decreases in the case of amplitude damping, phase damping and depolarising noise, and even it reaches zero for η = 1 in Brown et al. and Borras et al. channels.

This experiment was designed to test the string theory as a physical reality. The ground-based device placed the N poles of the magnets upwards, north, south, east, and west. Coil Ass'Y was placed between 2 N poles with bearing covers on the top and bottom. Gravity interacts to generate electricity in the Earth's direction or the opposite direction by the repulsive magnetic force. The voltage was measured from 3.60 to 3.80 sequentially while the generator was stationary through the monitor. The author found symmetry in Lex Tertia voltage and current zero data during experiment F4 6380 at a balanced state under gravity with the repulsive magnetic force. It generated from 42.8 to 794 μV in the vacuum chamber but from negative 16.1 to positive 18.3 μV in the air. As a result, the author measured more negative current and positive voltage generated in a vacuum. Trapped gravity was set to behave as free relativistic quantum particles or fluids in the magnetic sea. The result made it accessible to study the magnetic sea for different initial superpositions of positive- and negative-gravity spinor states. This might explain the relativistic quantum gravity exists as a physical reality, graviton interacting with photons to induce a magnetic field.

According to the quantum adiabatic theorem, we can in principle obtain a true vacuum of a quantum system starting from a trivial vacuum of a simple Hamiltonian. In actual adiabatic digital quantum simulation with finite time length and non-infinitesimal time steps, we can only obtain an approximate vacuum that is supposed to be a superposition of a true vacuum and excited states. We propose a procedure to improve the approximate vacuum.

Quantum information and communication technology will lead us to the new era of ultra-fast and absolute-secure networks. With the emergence of quantum supremacy on the horizon, the security of various classical encryption systems soon may be deemed obsolete. As a remedy, quantum key distribution (QKD) is proposed as a novel quantum-based secret keys exchange, which is developed to solve the problems of legacy encryption. It is anticipated that QKD will provide stronger security for future communication systems even in the presence of malicious quantum attacks. As the QKD research and development is getting mature, the theoretical use cases of QKD in various industries are proliferating. In this treatise, we summarise the potential applications of QKD for future communication technology while highlighting the ongoing standardisation efforts essential for the sustainability and reliability of the near-future deployment. Additionally, we also present the various challenges faced by both discrete variable and continuous variable QKD schemes hindering their widespread implementation into our future communication networks.

Quantum error detection has always been a fundamental challenge in a fault-tolerant quantum computer. Hence, it is of immense importance to detect and deal with arbitrary errors to efficiently perform quantum computation. Several error detection codes have been proposed and realised for lower number of qubit systems. Here we present an error detection code for a (2n + 1)-qubit entangled state using two syndrome qubits and simulate it on International Business Machines 16-qubit quantum computer for a 13-qubit entangled system. The code is able to detect an arbitrary quantum error in any one of the first 2n qubits of the (2n + 1)-qubit entangled state and detects any bit-flip error on the last qubit of the (2n + 1)-qubit entangled state via measurements on a pair of ancillary error syndrome qubits. The protocol presented here paves the way for designing error detection codes for the general higher number of entangled qubit systems.

Surface codes are quantum error correcting codes typically defined on a 2D array of qubits. A [d_x, d_z] surface code design is being introduced, where d_x(d_z) represents the distance of the code for bit (phase) error correction, motivated by the fact that the severity of bit flip and phase flip errors in the physical quantum system is asymmetric. We present pseudo-threshold and threshold values for the proposed surface code design for asymmetric error channels in the presence of various degrees of asymmetry of $��\text{Pauli}���\hat{X}�,���\hat{Y}���$, $��\text{and}���\hat{Z}��$ errors in a depolarisation channel. We demonstrate that compared to symmetric surface codes, our asymmetric surface codes can provide almost double the pseudo-threshold rates while requiring less than half the number of physical qubits in the presence of increasing asymmetry in the error channel. Our results show that for low degree of asymmetry, it is advantageous to increase d_x along with d_z. However, as the asymmetry of the channel increases, higher pseudo-threshold is obtained with increasing d_z when d_x is kept constant at a low value. Additionally, we also show that the advantage in the pseudo-threshold rates begins to saturate for any possible degree of asymmetry in the error channel as the surface code asymmetry is continued to be increased.

Quantum-dot cellular automaton (QCA) is efficient nanotechnology that may be used as an alternative to Complementary Metal Oxide Semiconductor technology. Here, computation relies upon the electron's polarisation, revealing binary information. Quantum-dot cellular automaton is an appropriate opportunity for the upcoming age of advanced digital frameworks. Security in transferring data is essential since a lot of valuable information is present. Digital Signature is a process where data is transferred from a receiver to an authenticated sender only. In this paper, tile-based Exclusive NOR gate (XNOR) is designed, which is more stable than the regular majority gate-based circuit. It is used to create a novel circuit for authentication of data which is based on tiles. It develops a QCA architecture that works on the principle of Digital Signature. The architecture validates and proves the authentication of the message sent from the sender to the receiver. The decrypted digest and the converted digest of the original dispatch are compared in the proposed Digital Validator circuit, which is developed utilising a QCA XNOR gate. The security for communication at the nanoscale level is enhanced due to the use of the SHA-256 algorithm. The simulation results confirm the theoretical results.