| 1. |
- Clausen, J, et al.
(författare)
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Nonclassical dynamics induced by a quantum meter
- 2005
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 72:6, s. 062104-
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Tidskriftsartikel (refereegranskat)abstract
- Conventionally, the effect of measurements on a quantum system is assumed to introduce decoherence, which renders the system classical- like. We consider here a microscopic meter, that is, an auxiliary essentially quantum system whose state is measured repeatedly, and show that it can be employed to induce transitions from classical states into inherently quantumlike states. The meter state is assumed to be lost in the environment and we derive a non- Markovian master equation for the dynamic system in the case of nondemolition coupling to the meter; this equation can be cast in the form of an (N-a)th- order differential equation in time, where N-a is the dimension of the meter basis. We apply the approach to a harmonic oscillator coupled to a spin-1/2 2 meter and demonstrate how it can be used to engineer effective Hamiltonian evolution, subject to decoherence induced by the projective meter measurements.
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| 2. |
- Kis, Z., et al.
(författare)
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Controlling material by light and light by material via adiabatic processes
- 2004
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Ingår i: Acta Physica Hungarica, Series B: Quantum Electronics. - : Akademiai Kiado Zrt.. - 1589-9535. ; 1:2/-, s. 161-164
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Tidskriftsartikel (refereegranskat)abstract
- We present a brief overview of our recent research in the field of adiabatic control of quantum mechanical processes. The most striking properties of the schemes that we study are their reliability and robustness, hence, they can be used not only for standard quantum control problems but for quantum computation as well.
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| 3. |
- Paul, H., et al.
(författare)
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The Stefan-Boltzmann law : two classical laws give a quantum one
- 2015
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Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0031-8949 .- 1402-4896. ; T165
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Tidskriftsartikel (refereegranskat)abstract
- Due to the universality of blackbody radiation the constant in the Stefan-Boltzmann law connecting the energy density and temperature of blackbody radiation is either a universal constant, or built out of several universal constants. Since the Stefan-Boltzmann law follows from thermodynamics and classical electrodynamics this constant must involve the speed of light and the Boltzmann constant. However, a dimensional analysis points to the existence of an additional universal constant not present in the two classical theories giving birth to the Stefan-Boltzmann law. In the most elementary version this constant has the dimension of an action and is thereby proportional to Planck's constant. We point out this unusual phenomenon of the combination of two classical laws creating a quantum law and speculate about its deeper origin.
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| 4. |
- Plimak, L. I., et al.
(författare)
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Operator ordering and causality
- 2012
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T147, s. 014026-
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Tidskriftsartikel (refereegranskat)abstract
- A formal implementation of the concepts of mesoscopic electromagnetic interaction and of the propagating wave in quantum electrodynamics beyond the rotating wave approximation is discussed. Used as a guide, these concepts lead to a natural resolution of a long-standing controversy: causality violations in the Glauber-Kelley-Kleiner photodetection theory. The Glauber-Kelley-Kleiner definition of the time-normal operator ordering must be amended without the rotating wave approximation, which eliminates all causality problems.
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| 5. |
- Plimak, L. I., et al.
(författare)
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Operator ordering and causality beyond the rotating wave approximation
- 2011
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 96:3, s. 34002-
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Tidskriftsartikel (refereegranskat)abstract
- Conventional definition of the time-normal operator ordering (KELLEY P. L. and KLEINER W. H., Phys. Rev., 136 (1964) A316) is prone to causality violations (de HAAN M., Physica A, 132 (1985) 375; 397). We show that such violations disappear if this definition is amended outside the rotating wave approximation. Nonrelativistic causality of an arbitrary time-normal product turns out to be a property of quantum kinematics, while relativistic causality is demonstrated for a time-normal product of two operators under the most general assumptions about quantum dynamics (commutativity of operators at space-like intervals). This eliminates the key obstacle preventing phase-space techniques of quantum optics from being extended to arbitrary quantum fields including fermions.
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