12,369 research outputs found
Gauge Invariant Formulation and Bosonisation of the Schwinger Model
The functional integral of the massless Schwinger model in dimensions
is reduced to an integral in terms of local gauge invariant quantities. It
turns out that this approach leads to a natural bosonisation scheme, yielding,
in particular the famous `bosonisation rule'' and giving some deeper insight
into the nature of the bosonisation phenomenon. As an application, the chiral
anomaly is calculated within this formulation.Comment: LaTeX, 8 page
Loss tolerant linear optical quantum memory by measurement-based quantum computing
We give a scheme for loss tolerantly building a linear optical quantum memory which itself is tolerant to qubit loss. We use the encoding recently introduced in Varnava et al 2006 Phys. Rev. Lett. 97 120501, and give a method for efficiently achieving this. The entire approach resides within the 'one-way' model for quantum computing (Raussendorf and Briegel 2001 Phys. Rev. Lett. 86 5188–91; Raussendorf et al 2003 Phys. Rev. A 68 022312). Our results suggest that it is possible to build a loss tolerant quantum memory, such that if the requirement is to keep the data stored over arbitrarily long times then this is possible with only polynomially increasing resources and logarithmically increasing individual photon life-times
Vibrational state dependence of ionic rotational branching ratios in resonance enhanced multiphoton ionization of CH
We show that rapid evolution of a Rydberg orbital with internuclear distance in a resonance enhanced multiphoton ionization (REMPI) process can have a profound influence on the production of molecular ions in alternative rotational states. This is illustrated by calculations of ionic rotational branching ratios for (2+1′) REMPI via the O11 (20.5) branch of the E′ ^2Σ^+(3pσ) Rydberg state of CH. The rotational propensity rule for ionization changes from ΔN=odd (ΔN=N_+−N_i) at lower vibrational excitation, as expected from the ΔN+l=odd selection rule, to ΔN=even at higher vibrational levels. This effect is expected to be quite general and should be most readily observable in diatomic hydrides
Anomalous Spin Dephasing in (110) GaAs Quantum Wells: Anisotropy and Intersubband Effects
A strong anisotropy of electron spin decoherence is observed in GaAs/(AlGa)As
quantum wells grown on (110) oriented substrate. The spin lifetime of spins
perpendicular to the growth direction is about one order of magnitude shorter
compared to spins along (110). The spin lifetimes of both spin orientations
decrease monotonically above a temperature of 80 and 120 K, respectively. The
decrease is very surprising for spins along (110) direction and cannot be
explained by the usual Dyakonov Perel dephasing mechanism. A novel spin
dephasing mechanism is put forward that is based on scattering of electrons
between different quantum well subbands.Comment: 4 pages, 3 postscript figures, corrected typo
Direct current superconducting quantum interferometers with asymmetric shunt resistors
We have investigated asymmetrically shunted Nb/Al-AlO/Nb direct current
(dc) superconducting quantum interference devices (SQUIDs). While keeping the
total resistance identical to a comparable symmetric SQUID with , we shunted only one of the two Josephson junctions with
. Simulations predict that the optimum energy resolution
and thus also the noise performance of such an asymmetric SQUID can
be 3--4 times better than that of its symmetric counterpart. Experiments at a
temperature of 4.2\,K yielded for an asymmetric
SQUID with an inductance of . For a comparable symmetric device
was achieved, confirming our simulation results.Comment: 5 pages, 4 figure
Verifying continuous-variable entanglement in finite spaces
Starting from arbitrary Hilbert spaces, we reduce the problem to verify
entanglement of any bipartite quantum state to finite dimensional subspaces.
Hence, entanglement is a finite dimensional property. A generalization for
multipartite quantum states is also given.Comment: 4 page
On the Structure of the Observable Algebra of QCD on the Lattice
The structure of the observable algebra of lattice
QCD in the Hamiltonian approach is investigated. As was shown earlier,
is isomorphic to the tensor product of a gluonic
-subalgebra, built from gauge fields and a hadronic subalgebra
constructed from gauge invariant combinations of quark fields. The gluonic
component is isomorphic to a standard CCR algebra over the group manifold
SU(3). The structure of the hadronic part, as presented in terms of a number of
generators and relations, is studied in detail. It is shown that its
irreducible representations are classified by triality. Using this, it is
proved that the hadronic algebra is isomorphic to the commutant of the triality
operator in the enveloping algebra of the Lie super algebra
(factorized by a certain ideal).Comment: 33 page
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