![]() ![]() In this work we show how knowledge of the direct and indirect parts of the solute-solvent PMF for water at the interface of a protein receptor can be used to gain insights about how to design tighter binding ligands. Standard, but powerful numerical methods can be used to estimate the solute-solvent PMF from which the indirect part can be extracted. Next, the density matrix approach is presented for perspective.Classical density functional theory (DFT) can be used to relate the thermodynamic properties of solutions to the indirect solvent mediated part of the solute-solvent potential of mean force (PMF). A more rigorous derivation in Dirac notation shows how decoherence destroys interference effects and the "quantum nature" of systems. Analogies are made between visualizable classical phase spaces and Hilbert spaces. The model requires some familiarity with quantum theory basics. To examine how decoherence operates, an "intuitive" model is presented below. The preservation of coherence, and mitigation of decoherence effects, are thus related to the concept of quantum error correction. Simply put, they require that the coherence of states be preserved and that decoherence be managed, in order to actually perform quantum computation. Moreover, observation indicates that this mixture looks like a proper quantum ensemble in a measurement situation, as the measurements lead to the "realization" of precisely one state in the "ensemble".ĭecoherence represents a challenge for the practical realization of quantum computers, since such machines are expected to rely heavily on the undisturbed evolution of quantum coherences. With respect to the measurement problem, decoherence provides an explanation for the transition of the system to a mixture of states that seem to correspond to those states observers perceive. A total superposition of the global or universal wavefunction still exists (and remains coherent at the global level), but its ultimate fate remains an interpretational issue. That is, components of the wave function are decoupled from a coherent system and acquire phases from their immediate surroundings. It only provides a framework for apparent wave-function collapse, as the quantum nature of the system "leaks" into the environment. Decoherence does not generate actual wave-function collapse. These have the effect of sharing quantum information with-or transferring it to-the surroundings.ĭecoherence has been used to understand the possibility of the collapse of the wave function in quantum mechanics. As with any coupling, entanglements are generated between the system and environment. Thus the dynamics of the system alone are irreversible. Viewed in isolation, the system's dynamics are non- unitary (although the combined system plus environment evolves in a unitary fashion). ĭecoherence can be viewed as the loss of information from a system into the environment (often modeled as a heat bath), since every system is loosely coupled with the energetic state of its surroundings. Decoherence has been developed into a complete framework, but there is controversy as to whether it solves the measurement problem, as the founders of decoherence theory admit in their seminal papers. Dieter Zeh and has been a subject of active research since the 1980s. As a result of this process, quantum behavior is apparently lost, just as energy appears to be lost by friction in classical mechanics.ĭecoherence was first introduced in 1970 by the German physicist H. If it is not perfectly isolated, for example during a measurement, coherence is shared with the environment and appears to be lost with time a process called quantum decoherence or environmental decoherence. ![]() If a quantum system were perfectly isolated, it would maintain coherence indefinitely, but it would be impossible to manipulate or investigate it. Coherence is preserved under the laws of quantum physics. A definite phase relationship is necessary to perform quantum computing on quantum information encoded in quantum states. As long as there exists a definite phase relation between different states, the system is said to be coherent. In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system a probabilistic interpretation of the wave function is used to explain various quantum effects. Quantum decoherence is the loss of quantum coherence, the process in which a system's behaviour changes from that which can be explained by quantum mechanics to that which can be explained by classical mechanics. ![]()
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