Entropy of a Quantum Oscillator coupled to a Heat Bath and implications for Quantum Thermodynamics

The free energy of a quantum oscillator in an arbitrary heat bath at a temperature T is given by a "remarkable formula" which involves only a single integral. This leads to a corresponding simple result for the entropy. The low temperature limit is examined in detail and we obtain explicit results both for the case of an Ohmic heat bath and a radiation heat bath. More general heat bath models are also examined. This enables us to determine the entropy at zero temperature in order to check the third law of thermodynamics in the quantum regimeComment: International Conference on "Frontiers of Quantum and Mesoscopic Thermodynamics

Decoherence in Nanostructures and Quantum Systems

Decoherence phenomena are pervasive in the arena of nanostructures but perhaps even more so in the study of the fundamentals of quantum mechanics and quantum computation. Since there has been little overlap between the studies in both arenas, this is an attempt to bridge the gap. Topics stressed include (a) wave packet spreading in a dissipative environment, a key element in all arenas, (b) the definition of a quantitative measure of decoherence, (c) the near zero and zero temperature limit, and (d) the key role played by initial conditions: system and environment entangled at all times so that one must use the density matrix (or Wigner distribution) for the complete system or initially decoupled system and environment so that use of a reduced density matrix or reduced Wigner distribution is feasible. Our approach utilizes generalized quantum Langevin equations and Wigner distributions

The Expansion of the Universe and the Cosmological Constant Problem

The discovery that the expansion of the universe is accelerating in time is a major discovery which still awaits adequate explanation. It is generally agreed that this implies a cosmic repulsion as a result of the existence of a cosmological constant . However, estimates of the cosmological constant, based on calculations of the zero-point fluctuations of quantum fields are too large by over a hundred orders of magnitude. This result is obtained by summing the zero-point energies up to a large cutoff energy, based on the Planck scale. Since there is no compelling reason for this choice, we argue that since all known quantum electrodynamic (QED) effects involves interaction with matter, a preferred choice should be based on causality and other considerations, leading to a much lower value for the cosmological constant .Comment: Phys. Lett. A, in pres

Entanglement without Dissipation: A Touchstone for an exact Comparison of Entanglement Measures

Entanglement, which is an essential characteristic of quantum mechanics, is the key element in potential practical quantum information and quantum communication systems. However, there are many open and fundamental questions (relating to entanglement measures, sudden death, etc.) that require a deeper understanding. Thus, we are motivated to investigate a simple but non-trivial correlated two-body continuous variable system in the absence of a heat bath, which facilitates an \underline{exact} measure of the entanglement at all times. In particular, we find that the results obtained from all well-known existing entanglement measures agree with each other but that, in practice, some are more straightforward to use than others

Use of Nitrapyrin to reduce nitrogen losses in western Canada

Non-Peer ReviewedNitrapyrin is a potent nitrification inhibitor from Dow AgroSciences Canada that keeps more nitrogen in the root zone by delaying the conversion of NH4 to NO3 in the soil. Two formulations of nitrapyrin are now approved for use in Canada: N-Serve ™, an emulsifiable concentrate formulation for use with NH3, and Ntrench™, a water-based micro-encapsulated formulation for use with urea, urea ammonium nitrate (UAN) and liquid manure. In 2013 and 2014, performance of eNtrench and N-Serve in spring preplant applications with urea, UAN or NH3 was evaluated in twenty field research trials conducted in Alberta, Saskatchewan and Manitoba. All treatments were banded or injected into the soil, or broadcast applied and incorporated, prior to planting of spring wheat or canola. Primary assessments were soil nitrogen balance (NH4-N and NO3-N) at depths of 0 to 30 and 30 to 60 cm from samples collected 2, 4 and 6 weeks after crop emergence (WAE). Averaged across trials, application of eNtrench with urea or UAN increased the amount of NH4-N in the soil (0 to 60 cm) by 29, 13 and 12% at 2, 4 and 6 WAE,respectively, relative to application of urea or UAN. In a subset of trials conducted on coarse-textured soils, eNtrench also decreased the amount of NO3-N moving below the root zone to the 30 to 60 cm depth range by 26 and 16% at 4 and 6 WAE, respectively. Application of N-Serve with NH3 increased the amount of NH4-N in the soil (0 to 60 cm) by an average of 21, 59 and 63% at 2, 4 and 6 WAE, respectively, relative to application of NH3. N-Serve also decreased the amount of NO3-N moving below the root zone to the 30 to 60 cm depth range by 32, 30 and 18% at 2, 4 and 6 WAE, respectively. eNtrench and N-Serve will provide Canadian farmers with new tools to optimize crop yield and improve nitrogen use efficiency by keeping more nitrogen in the stable NH4-form and reducing losses associated with NO3 leaching or denitrification. ™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Do

Radiation Reaction: General approach and applications, especially to electrodynamics

Radiation reaction (but, more generally, fluctuations and dissipation) occurs when a system interacts with a heat bath, a particular case being the interaction of an electron with the radiation field. We have developed a general theory for the case of a quantum particle in a general potential (but, in more detail, an oscillator potential) coupled to an arbitrary heat bath at arbitrary temperature, and in an external time-dependent $c$-number field. The results may be applied to a large variety of problems in physics but we concentrate by showing in detail the application to the blackbody radiation heat bath, giving an exact result for radiation reaction problem which has no unsatisfactory features such as the runaway solutions associated with the Abraham-Lorentz theory. In addition, we show how atomic energy and free energy shifts due to temperature may be calculated. Finally, we give a brief review of applications to Josephson junctions, quantum statistical mechanics, mesoscopic physics, quantum information, noise in gravitational wave detectors, Unruh radiation and the violation of the quantum regression theore

Charge Effects on Gravitational Wave Detectors

We show that the mean-square displacement of a charged oscillator due to the zero point oscillations of the radiation field is unique in the sense that it is very sensitive to the value of the bare mass of the charge. Thus, a controlled experiment using gravitational wave detectors could lead to a determination of the electron bare mass and shed some light on quantum electrodynamic theory. We also speculate that the irregular signals of non-gravitational origin often observed in gravitational wave bar detectors could be caused by stray charges and that such charges could also adversely affect LIGO and other such detector

Analytical and numerical investigation of escape rate for a noise driven bath

We consider a system-reservoir model where the reservoir is modulated by an external noise. Both the internal noise of the reservoir and the external noise are stationary, Gaussian and are characterized by arbitrary decaying correlation functions. Based on a relation between the dissipation of the system and the response function of the reservoir driven by external noise we numerically examine the model using a full bistable potential to show that one can recover the turn-over features of the usual Kramers' dynamics when the external noise modulates the reservoir rather than the system directly. We derive the generalized Kramers' rate for this nonequilibrium open system. The theoretical results are verified by numerical simulation.Comment: Revtex, 25 pages, 5 figures. To appear in Phys. Rev.

Comparative Chromosome Maps of Neotropical Rodents Necromys lasiurus and Thaptomys nigrita (Cricetidae) Established by ZOO-FISH

This work presents chromosome homology maps between Mus musculus (MMU) and 2 South American rodent species from the Cricetidae group: Necromys lasiurus (NLA, 2n = 34) and Thaptomys nigrita (TNI, 2n = 52), established by ZOO-FISH using mouse chromosome-specific painting probes. Extending previous molecular cytogenetic studies in Neotropical rodents, the purpose of this work was to delineate evolutionary chromosomal rearrangements in Cricetidae rodents and to reconstruct the phylogenetic relationships among the Akodontini species. Our phylogenetic reconstruction by maximum parsimony analysis of chromosomal characters confirmed one consistent clade of all Neotropical rodents studied so far. In both species analyzed here, we observed the syntenic association of chromosome segments homologous to MMU 8/13, suggesting that this chromosome form is a synapomorphic trait exclusive to Neotropical rodents. Further, the previously described Akodontini-specific syntenic associations MMU 3/18 and MMU 6/12 were observed in N. lasiurus but not in T. nigrita, although the latter species is considered a member of the Akodontini tribe by some authors. Finally, and in agreement with this finding, N. lasiurus and Akodon serrensis share the derived fission of MMU 13, which places them as basal sister clades within Akodontini. Copyright (C) 2011 S. Karger AG, Base

Dynamical description of quantum computing: generic nonlocality of quantum noise

We develop dynamical non-Markovian description of quantum computing in weak coupling limit, in lowest order approximation. We show that long range memory of quantum reservoir produces strong interrelation between structure of noise and quantum algorithm, implying nonlocal attacks of noise. We then argue that the quantum error correction method fails to protect quantum computation against electromagnetic or phonon vacuum which exhibit $1/t^4$ memory. This shows that the implicit assumption of quantum error correction theory -- independence of noise and self-dynamics -- fails in long time regimes. We also use our approach to present {\it pure} decoherence and decoherence accompanied by dissipation in terms of spectral density of reservoir. The so-called {\it dynamical decoupling} method is discussed in this context. Finally, we propose {\it minimal decoherence model}, in which the only source of decoherence is vacuum. We optimize fidelity of quantum information processing under the trade-off between speed of gate and strength of decoherence.Comment: 12 pages, minor corrections, softened interpretation of the result