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Full-Text Articles in Physical Sciences and Mathematics
A New Look At The Quantum Liouville Theorem, P. T. Leung, G. I. Ni
A New Look At The Quantum Liouville Theorem, P. T. Leung, G. I. Ni
Physics Faculty Publications and Presentations
We clarify certain confusions in the literature of the density operator in quantum mechanics, and demonstrate that the quantum Liouville theorem has the same form in both the Schrodinger and the Heisenberg pictures. Our starting point is to treat the density operator as an observable which has its specific time dependence in each of the two pictures. It is further shown that such a formulation will provide the exact correspondence between classical and quantum statistical mechanics with the Liouville theorem being interpreted as a conservation law, which is derivable from the equation of motion only in the quantum case.
Class Of Unambiguous State Discrimination Problems Achievable By Separable Measurements But Impossible By Local Operations And Classical Communication, Scott M. Cohen
Physics Faculty Publications and Presentations
We consider an infinite class of unambiguous quantum state discrimination problems on multipartite systems, described by Hilbert space H, of any number of parties. Restricting consideration to measurements that act only on H, we find the optimal global measurement for each element of this class, achieving the maximum possible success probability of 1/2 in all cases. This measurement turns out to be both separable and unique, and by our recently discovered necessary condition for local quantum operations and classical communication (LOCC) it is easily shown to be impossible by any finite-round LOCC protocol. We also show that, quite generally, if …
Local Quantum Protocols For Separable Measurements With Many Parties, Scott M. Cohen
Local Quantum Protocols For Separable Measurements With Many Parties, Scott M. Cohen
Physics Faculty Publications and Presentations
In a recent paper [ S. M. Cohen Phys. Rev. A 84 052322 (2011)], we showed how to construct a protocol for implementing a bipartite, separable quantum measurement using only local operations on subsystems and classical communication between parties (LOCC) within any fixed number of rounds of communication, whenever such a protocol exists. Here, we generalize that construction to one that applies for any number of parties. One important observation is that the construction automatically determines the ordering of the parties' measurements, overcoming a significant apparent difficulty in designing protocols for more than two parties. We also present various other …
Relativistic Corrections To The Bethe Sum Rule, P.T. Leung, M. L. Rustgi, S. A. Long
Relativistic Corrections To The Bethe Sum Rule, P.T. Leung, M. L. Rustgi, S. A. Long
Physics Faculty Publications and Presentations
Relativistic corrections to order alpha² to the Bethe sum rule have been obtained for a one-electron system employing the Foldy-Wouthuysen transformation. The results have wide applications in high-Z systems at large momentum transfers.
New Method For Generating Density Expansions, John D. Ramshaw
New Method For Generating Density Expansions, John D. Ramshaw
Physics Faculty Publications and Presentations
The calculus of finite differences is used to develop a new method for expressing the thermodynamic limit of a reasonably arbitrary statistical?mechanical average as a power series in the number density ?. The method is simple, straightforward, and purely analytic: it involves no intermediate expansion in powers of the activity and it avoids the use of graph theory. Moreover, the method is developed independently of the prescription for computing the statistical average, a fact which lends to the results an especially wide range of applicability. In particular, these results may be used in classical or quantum statistical mechanics, for intermolecular …