Results 1 
8 of
8
Interpreting the Quantum
, 1997
"... This paper is a commentary on the foundational significance of the CliftonBubHalvorson theorem characterizing quantum theory in terms of three informationtheoretic constraints. I argue that: (1) a quantum theory is best understood as a theory about the possibilities and impossibilities of informa ..."
Abstract

Cited by 16 (1 self)
 Add to MetaCart
This paper is a commentary on the foundational significance of the CliftonBubHalvorson theorem characterizing quantum theory in terms of three informationtheoretic constraints. I argue that: (1) a quantum theory is best understood as a theory about the possibilities and impossibilities of information transfer, as opposed to a theory about the mechanics of nonclassical waves or particles, (2) given the informationtheoretic constraints, any mechanical theory of quantum phenomena that includes an account of the measuring instruments that reveal these phenomena must be empirically equivalent to a quantum theory, and (3) assuming the informationtheoretic constraints are in fact satisfied in our world, no mechanical theory of quantum phenomena that includes an account of measurement interactions can be acceptable, and the appropriate aim of physics at the fundamental level then becomes the representation and manipulation of information.
Newtonian Quantum Gravity
, 1995
"... We develop a nonlinear quantum theory of Newtonian gravity consistent with an objective interpretation of the wavefunction. Inspired by the ideas of Schrödinger, and Bell, we seek a dimensional reduction procedure to map complex wavefunctions in configuration space onto a family of observable fields ..."
Abstract

Cited by 3 (0 self)
 Add to MetaCart
We develop a nonlinear quantum theory of Newtonian gravity consistent with an objective interpretation of the wavefunction. Inspired by the ideas of Schrödinger, and Bell, we seek a dimensional reduction procedure to map complex wavefunctions in configuration space onto a family of observable fields in space–time. Consideration of quasi–classical conservation laws selects the reduced one–body quantities as the basis for an explicit quasi–classical coarse–graining. These we interpret as describing the objective reality of the laboratory. Thereafter, we examine what may stand in the role of the usual Copenhagen observer to localize this quantity against macroscopic dispersion. Only a tiny change is needed, via a generically attractive self–potential. A nonlinear treatment of gravitational self–energy is thus advanced. This term sets a scale for all wavepackets. The Newtonian cosmology is thus closed, without need of an external observer. Finally, the concept of quantization is re–interpreted as a nonlinear eigenvalue problem. To illustrate, we exhibit an elementary family of gravitationally self–bound solitary waves. Contrasting this theory with its canonically quantized analogue, we find that the given interpretation is empirically distinguishable, in principle. This result encourages deeper study of nonlinear field theories as a testable alternative to canonically quantized gravity. Expanded version of a talk presented at the Inaugural Australian General Relativity Workshop,
Orthogonality and boundary conditions in quantum mechanics”, BenGurion University preprint
 Foundations of Physics
, 1998
"... Onedimensional particle states are constructed according to orthogonality conditions, without requiring boundary conditions. Free particle states are constructed using Dirac’s delta function orthogonality conditions. The states (doublets) depend on two quantum numbers: energy and parity (”+ ” or ” ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
Onedimensional particle states are constructed according to orthogonality conditions, without requiring boundary conditions. Free particle states are constructed using Dirac’s delta function orthogonality conditions. The states (doublets) depend on two quantum numbers: energy and parity (”+ ” or ””). With the aid of projection operators the particles are confined to a constrained region, in a way similar to the action of an infinite well potential. From the resulting overcomplete basis only the mutually orthogonal states are selected. Four solutions are found, corresponding to different noncommuting Hamiltonians. Their energy eigenstates are labeled with the main quantum number n and parity ”+ ” or ””. The energy eigenvalues are functions of n only. The four cases correspond to different boundary conditions: (I) the wave function vanishes on the boundary (energy levels: 1 +,2 −,3 +,4 −,...), (II) the derivative of the wavefunction vanishes on the boundary (energy levels 0 +,1 −,2 +,3 −,...), (III) periodic boundary conditions (energy levels: 0 +,2 +,2 −,4 +,4 − 6 +,6 −,...), (IV) periodic boundary conditions (energy levels: 1 +,1 −,3 +,3 −,5 +,5 −,...). Among the four cases, only solution (III) forms a complete basis in the sense that any function in the constrained region, can be expanded with it. By extending the boundaries of the constrained region to infinity, only solution (III) converges uniformly to the free particle states. Orthogonality seems to be a more basic requirement than boundary conditions. By using projection operators, confinement of the particle to a definite region can be achieved in a conceptually simple and unambiguous way, and physical operators can be written so that they act only in the confined region. Permanent address. 1 Key words: confinement, orthogonality, boundary conditions, Dirac’s formalism, projection operators.
Continuoustime Quantum Algorithms: Searching and Adiabatic Computation
, 2002
"... One of the most important quantum algorithms is Grover's search algorithm [G96]. Quantum searching can be used to speed up the search for solutions to NPcomplete problems e.g. 3SAT. Even so, the best known quantum algorithms for 3SAT are considered inefficient. ..."
Abstract

Cited by 1 (1 self)
 Add to MetaCart
One of the most important quantum algorithms is Grover's search algorithm [G96]. Quantum searching can be used to speed up the search for solutions to NPcomplete problems e.g. 3SAT. Even so, the best known quantum algorithms for 3SAT are considered inefficient.
Helicity and the Electromagnetic Field
, 2001
"... this paper is based is that a theory be developed according to its fundamental underlying symmetry: for the electromagnetic field this is the symmetry of special relativity [15], a sub symmetry of general relativity. We accept the Poincar group as the group of special relativity, with ten generato ..."
Abstract
 Add to MetaCart
this paper is based is that a theory be developed according to its fundamental underlying symmetry: for the electromagnetic field this is the symmetry of special relativity [15], a sub symmetry of general relativity. We accept the Poincar group as the group of special relativity, with ten generators and two invariants [6]. The electromagnetic field is considered to be a physical entity which is described by symmetry guided relations between group generators according to the following prescription [15]. Rotation generators are those of magnetic field components; boost generators are those of electric field components; translation generators are those of four potential components. It is shown in Sec. 2 that the Lie algebra of the Poincar group leads to relations between generator eigenvalues which, using the above prescription, are consistent with the Maxwell equations and recently inferred [15] cyclic relations between field components. Section 3 develops a helicity equation [7] from the underlying symmetry of the Poincar group as given in Sec. 2. This equation has been inferred independently by Dvoeglazov [8] and by Afanasev and Stepanofsky [9], following the introduction of relativistic field helicity by Ranada [10], and the earlier realization that helicity is a topological invariant [11]. The transition from the static symmetry characteristics of the Poincar group to an equation of motion (the helicity equation) is accomplished through the transition from momentum to coordinate representation P is replaced by i , where P is the translation generator. This is synonymous with the well known quantum hypothesis, which is a successful calculating prescription in field theory and wave mechanics. This transition changes the fundamental group identity [12], P ...
Radiation Induced Fermion Resonance
, 1998
"... The Dirac equation is solved for two novel terms which describe the interaction energy between the half integral spin of a fermion and the classical, circularly polarized, electromagnetic field. A simple experiment is suggested to test the new terms and the existence of radiation induced fermion res ..."
Abstract
 Add to MetaCart
The Dirac equation is solved for two novel terms which describe the interaction energy between the half integral spin of a fermion and the classical, circularly polarized, electromagnetic field. A simple experiment is suggested to test the new terms and the existence of radiation induced fermion resonance. Recently, Warren et al. [1,2] have made the first attempt to detect radiation induced fermion resonance due to irradiation by a circularly polarized electromagnetic field [36]. In this Letter the Dirac equation is solved for one fermion in a classical electromagnetic field. Two new terms are inferred which show the theoretical existence of radiation induced fermion resonance, and the experimental conditions under which this phenomenon can be detected are defined for an electron beam. The demonstration is based on the standard Dirac Hamiltonian operator (Gaussian units), H = c⃗α · ⃗p − e c ⃗) A + βmc 2 + eV, (1) describing a fermion (e.g. an electron) of mass m and charge e interacting with a classical electromagnetic field with vector potential A µ = V, ⃗) A. (2) through the eigenvalue equation, Hψ = Eψ, (3) Here ⃗α and β are the usual Dirac matrices and ψ the fourcomponent Dirac spinor. The rest energy of the fermion is mc2 and its three momentum is ⃗p, as usual. In the usual nonrelativistic approximation the calculation proceeds by setting up Eq. (3) for the proper dominant wavefunction, φ, H ′ φ = Eφ, (4) Writing the 4component Dirac spinor ψ = ψA ψB where ψA and ψB are respectively the “large ” and “small ” component satisfying the condition (at second order in v/c)
Open Access
"... On the interchannel interference in digital communication systems, its impulsive nature, and its mitigation Alexei V Nikitin 1,2 A strong digital communication transmitter located in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respec ..."
Abstract
 Add to MetaCart
On the interchannel interference in digital communication systems, its impulsive nature, and its mitigation Alexei V Nikitin 1,2 A strong digital communication transmitter located in close physical proximity to a receiver of a weak signal can noticeably interfere with the latter even when the respective channels are tens or hundreds of megahertz apart. When time domain observations are made in the signal chain of the receiver between the first mixer and the baseband, this interference is likely to appear impulsive. Understanding the mechanism of this interference is important for its effective mitigation. In this article, we show that impulsiveness, or a high degree of peakedness, of interchannel interference in communication systems results from the nonsmooth nature of any physically realizable modulation scheme for transmission of a digital (discontinuous) message. Even modulation schemes designed to be ‘smooth’, e.g., continuousphase modulation, are, in fact, not smooth because their higher order time derivatives still contain discontinuities. When observed by an outofband receiver, the transmissions from these discontinuities may appear as strong transients with the peak power noticeably exceeding the average power, and the received signal will have a high degree of peakedness. This impulsive nature of the interference provides an opportunity to reduce its power by nonlinear filtering, thus improving quality of the receiver channel.