3,065 research outputs found
Existence of Time Operator for a Singular Harmonic Oscillator
The time operator for a quantum singular oscillator of the
Calogero-Sutherland type is constructed in terms of the generators of the
SU(1,1) group. In the space spanned by the eigenstates of the Hamiltonian, the
time operator is not self-adjoint. We show, that the time-energy uncertainty
relation can be given the meaning within the Barut-Girardello coherent states
defined for the singular oscillator.We have also shown the relationship with
the time-of-arrival operator of Aharonov and Bohm.Comment: 7 pages, no figures, LaTex, submitted to Concepts of Physic
Quantum Horizons and Space-Time Non-Commutativity
We study dynamics of a scalar field in the near-horizon region described by a
static Klein-Gordon operator which is the Hamiltonian of the system. The
explicite construction of a time operator near-horizon is given and its
self-adjointness discussed.Comment: LaTex, 6 pages, no figures, Expanded version of a poster presented at
5 European Advanced Study Conference in Ancient Olympia, Greece, July 2004.
to appear in a special issue of IJB
Need for the intensity-dependent pion-nucleon coupling in multipion production processes
We give reasons in support of the use of an effective intensity-dependent
pion-nucleon coupling Hamiltonian for describing the properties of the pion
multiplicity distribution and the corresponding factorial moments within the
thermal-density matrix approach.We explain the appearance of the
negative-binomial (NB) distribution for pions and the well-known empi- rical
relation of Wroblewski.Our model Hamiltonian is written as a linear combination
of the generators of the SU(1,1) group.We find the generating function for the
pion multiplicity distribution at finite temperature T and discuss the
properties of the second-order factorial moment.Also, we show that an
intensity-dependent pion-nucleon coupling generates the squeezed states of the
pion field. At T=0, these squeezed states become an inherent property of the NB
distribution.Comment: 18 pages, no figures, late
Intensity-dependent pion-nucleon coupling in multipion production processes
We propose an intensity-dependent pion-nucleon coupling Hamiltonian within a
unitary multiparticle-production model of the Auerbach-
Avin-Blankenbecler-Sugar (AABS) type in which the pion field is represented by
the thermal-density matrix.Using this Hamiltonian, we explain the appearance of
the negative-binomial (NB) distribution for pions and the well-known empirical
relation, the so-called Wr\' oblewski relation, in which the dispersion of
the pion- multiplicity distribution is linearly related to the average
multiplicity : , with the coefficient . The
Hamiltonian of our model is expressed linearly in terms of the generators of
the group.We also find the generating function for the pion field,
which reduces to the generating function of the NB distribution limit .Comment: 16 pages, no pictures, late
Disoriented Chiral Condensate and Charge-Neutral Particle Fluctuations in Heavy Ion Collisions
The posibility of large charge and isospin fluctuations in high-energy heavy
ion-collisions is studied within the framework of the nonlinear -model
with quark degrees of freedom. The multipion exchange potential between two
quarks is derived. It is shown that the soft chiral pion bremsstralung leads to
anomalously large fluctuations in the ratio of neutral to charged pions,
predicted by the formation of a disoriented chiral condensate (DCC). The
factorization property of the scattering amplitude in the impact parameter
space of the leading two-nucleon system is used to study semiclassical
production of pions in the central region. We show that the DCC-type
fluctuations are suppressed if a large number of pions are produced in -type clusters. Our conclusion is supported through the calculation of two
pion correlation parameters as a function of the -to- ratio.Comment: 20 pages, 2 figures, NAPP 2003 Conference,Dubrovnik. submitted to
Fizika
Disoriented Chiral Condensates and Anomalous Production of Pions
The leading-particle effect and the factorization property of the scattering
amplitude in the impact parameter space are used to study semiclassical
production of pions in the central region. The mechanism is related to the
isospin-uniform solution of the nonlinear -model coupled to quark
degrees of freedom. The multipion exchange potential between two quarks is
derived. It is shown thatthe soft chiral pion bremsstralung also leads to
anomalously large fluctuations in the ratio of neutral to charged pions. We
show that only direct production ofpions in the form of an isoscalar coherent
pulse without isovector pairs can lead to large neutral-charged fluctuations.Comment: Latex, 22 pages, 2 figure
Qubit metrology for building a fault-tolerant quantum computer
Recent progress in quantum information has led to the start of several large
national and industrial efforts to build a quantum computer. Researchers are
now working to overcome many scientific and technological challenges. The
program's biggest obstacle, a potential showstopper for the entire effort, is
the need for high-fidelity qubit operations in a scalable architecture. This
challenge arises from the fundamental fragility of quantum information, which
can only be overcome with quantum error correction. In a fault-tolerant quantum
computer the qubits and their logic interactions must have errors below a
threshold: scaling up with more and more qubits then brings the net error
probability down to appropriate levels ~ needed for running complex
algorithms. Reducing error requires solving problems in physics, control,
materials and fabrication, which differ for every implementation. I explain
here the common key driver for continued improvement - the metrology of qubit
errors.Comment: 4 pages, 2 figure
On the Gravitational Energy Shift for matter waves
The gravitational energy shift for photons is extended to all mass-equivalent
energies , obeying the quantum condition .On an example of
a relativistic binary system, it was shown that the gravitational energy shift
would imply,in contrast to Newtonian gravity, the gravitational attraction
between full mass-equivalent energies. The corresponding space-time metric
becomes exponential. A good agreement was found with all results of weak field
tests of General relativity. The strong field effects in a binary system can be
easily studied. A long standing problems of Pioneer and other flyby anomalies
were also discussed in connection with the violation of total energy
conservation. It was shown that relatively small energy non-conservation during
the change of the orbit type could explain these persistent anomalies.Comment: 7 page
Time Operator for a Quantum Singular Oscillator
The problem of existence of a self-adjoint time operator conjugate to a
Hamiltonian with SU(1,1) dynamical symmetry is investigated. In the space
spanned by the eigenstates of the generator of the SU(1,1) group, the
time operator for the quantum singular harmonic potential of the form is constructed explicitly, and shown that it is related to the
time-of-arrival operator of Aharonov and Bohm. Our construction is fully
algebraic, involving only the generators of the SU(1,1) group.Comment: 11 pages, LaTeX, added one new referenc
Superconducting Qubits and the Physics of Josephson Junctions
We describe in this paper how the nonlinear Josephson inductance is the
crucial circuit element for all Josephson qubits. We discuss the three types of
qubit circuits, and show how these circuits use this nonlinearity in unique
manners. We give a brief derivation of the BCS theory, highlighting the
appearance of the macroscopic phase parameter. The Josephson equations are
derived using standard first and second order perturbation theory that describe
quasiparticle and Cooper-pair tunneling. An exact calculation of the Josephson
effect then follows using the quasiparticle bound-state theory, and then expand
upon this theory to describe quasiparticle excitations as transitions from the
ground to excited bound states from nonadiabatic changes in the bias. Although
quasiparticle current is typically calculated only for a constant DC voltage,
the advantage to this approach is seen where we qualitatively describe
quasiparticle tunneling with AC voltage excitations, as appropriate for the
qubit state. This section describes how the Josephson qubit is typically
insensitive to quasiparticle damping, even to the extent that a phase qubit can
be constructed from microbridge junctions.Comment: Submitted to Les Houches conference proceeding
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