72 063623 (2005) .
... In Fig. 1, we plot the snapshots of the orbits at times of multiple period and get the Poincaré section of the phase space for a pair of variables 共Sz , 兲, i.e., z-component spin and the azimuthal angle. It shows one big island and four small islands. Inside the islands motions are stable, outside ...
... In Fig. 1, we plot the snapshots of the orbits at times of multiple period and get the Poincaré section of the phase space for a pair of variables 共Sz , 兲, i.e., z-component spin and the azimuthal angle. It shows one big island and four small islands. Inside the islands motions are stable, outside ...
Quantum Structures
... theory. Is it an epistemic state (representing knowledge, information, or belief) or an ontic state (a direct reflection of reality)? In the ontological models framework, quantum states correspond to probability measures over more fundamental states of reality. The quantum state is then ontic if eve ...
... theory. Is it an epistemic state (representing knowledge, information, or belief) or an ontic state (a direct reflection of reality)? In the ontological models framework, quantum states correspond to probability measures over more fundamental states of reality. The quantum state is then ontic if eve ...
Structural Explanations, or the Reasonable Effectiveness of
... However, the admission that our best theory of the fundamental constituents of matter cannot explain the phenomena it describes represent a strong argument against the view that explanation is a legitimate aim of science, and this conclusion is regarded by the vast majority of philosophers as unacce ...
... However, the admission that our best theory of the fundamental constituents of matter cannot explain the phenomena it describes represent a strong argument against the view that explanation is a legitimate aim of science, and this conclusion is regarded by the vast majority of philosophers as unacce ...
Stability of local quantum dissipative systems
... Dissipative quantum systems Let H be a finite-dimensional Hilbert space. A dissipative quantum system is given by a 1-parameter continuous semigroup (Tt )t>0 of completely positive, trace preserving (CPTP) maps (also called quantum channels): Tt : B(H) → B(H) ...
... Dissipative quantum systems Let H be a finite-dimensional Hilbert space. A dissipative quantum system is given by a 1-parameter continuous semigroup (Tt )t>0 of completely positive, trace preserving (CPTP) maps (also called quantum channels): Tt : B(H) → B(H) ...
Resonances, dissipation and decoherence in exotic and artificial atoms
... necessary modifications are to include the effects of the lattice and to replace the Coulomb potential of the nucleus by an appropriate model of the artificial confinement in the quantum dot, while the electron-electron interaction can be approached exactly in the same way. This raises the question ...
... necessary modifications are to include the effects of the lattice and to replace the Coulomb potential of the nucleus by an appropriate model of the artificial confinement in the quantum dot, while the electron-electron interaction can be approached exactly in the same way. This raises the question ...
Quantum key distribution
Quantum key distribution (QKD) uses quantum mechanics to guarantee secure communication. It enables two parties to produce a shared random secret key known only to them, which can then be used to encrypt and decrypt messages. It is often incorrectly called quantum cryptography, as it is the most well known example of the group of quantum cryptographic tasks.An important and unique property of quantum key distribution is the ability of the two communicating users to detect the presence of any third party trying to gain knowledge of the key. This results from a fundamental aspect of quantum mechanics: the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies. By using quantum superpositions or quantum entanglement and transmitting information in quantum states, a communication system can be implemented which detects eavesdropping. If the level of eavesdropping is below a certain threshold, a key can be produced that is guaranteed to be secure (i.e. the eavesdropper has no information about it), otherwise no secure key is possible and communication is aborted.The security of encryption that uses quantum key distribution relies on the foundations of quantum mechanics, in contrast to traditional public key cryptography which relies on the computational difficulty of certain mathematical functions, and cannot provide any indication of eavesdropping at any point in the communication process, or any mathematical proof as to the actual complexity of reversing the one-way functions used. QKD has provable security based on information theory, and forward secrecy.Quantum key distribution is only used to produce and distribute a key, not to transmit any message data. This key can then be used with any chosen encryption algorithm to encrypt (and decrypt) a message, which can then be transmitted over a standard communication channel. The algorithm most commonly associated with QKD is the one-time pad, as it is provably secure when used with a secret, random key. In real world situations, it is often also used with encryption using symmetric key algorithms like the Advanced Encryption Standard algorithm. In the case of QKD this comparison is based on the assumption of perfect single-photon sources and detectors, that cannot be easily implemented.