152 research outputs found
Accelerated Detectors and Temperature in (Anti) de Sitter Spaces
We show, in complete accord with the usual Rindler picture, that detectors
with constant acceleration in de Sitter (dS) and Anti de Sitter (AdS)
spaces with cosmological constants measure temperatures , the detector "5-acceleration" in the
embedding flat 5-space. For dS, this recovers a known result; in AdS, where
is negative, the temperature is well defined down to the critical
value , again in accord with the underlying kinematics. The existence
of a thermal spectrum is also demonstrated for a variety of candidate wave
functions in AdS backgrounds.Comment: Latex +2 Fi
The state space for two qutrits has a phase space structure in its core
We investigate the state space of bipartite qutrits. For states which are
locally maximally mixed we obtain an analog of the ``magic'' tetrahedron for
bipartite qubits--a magic simplex W. This is obtained via the Weyl group which
is a kind of ``quantization'' of classical phase space. We analyze how this
simplex W is embedded in the whole state space of two qutrits and discuss
symmetries and equivalences inside the simplex W. Because we are explicitly
able to construct optimal entanglement witnesses we obtain the border between
separable and entangled states. With our method we find also the total area of
bound entangled states of the parameter subspace under intervestigation. Our
considerations can also be applied to higher dimensions.Comment: 3 figure
The Reeh-Schlieder property for thermal field theories
We show that the Reeh-Schlieder property w.r.t. the KMS-vector is a direct
consequence of locality, additivity and the relativistic KMS-condition. The
latter characterises the thermal equilibrium states of a relativistic quantum
field theory. The statement remains vaild even if the given equilibrium state
breaks spatial translation invariance.Comment: plain tex, 10 page
A special simplex in the state space for entangled qudits
Focus is on two parties with Hilbert spaces of dimension d, i.e. "qudits". In
the state space of these two possibly entangled qudits an analogue to the well
known tetrahedron with the four qubit Bell states at the vertices is presented.
The simplex analogue to this magic tetrahedron includes mixed states. Each of
these states appears to each of the two parties as the maximally mixed state.
Some studies on these states are performed, and special elements of this set
are identified. A large number of them is included in the chosen simplex which
fits exactly into conditions needed for teleportation and other applications.
Its rich symmetry - related to that of a classical phase space - helps to study
entanglement, to construct witnesses and perform partial transpositions. This
simplex has been explored in details for d=3. In this paper the mathematical
background and extensions to arbitrary dimensions are analysed.Comment: 24 pages, in connection with the Workshop 'Theory and Technology in
Quantum Information, Communication, Computation and Cryptography' June 2006,
Trieste; summary and outlook added, minor changes in notatio
Geometric phases of scattering states in a ring geometry: adiabatic pumping in mesoscopic devices
Geometric phases of scattering states in a ring geometry are studied based on
a variant of the adiabatic theorem. Three time scales, i.e., the adiabatic
period, the system time and the dwell time, associated with adiabatic
scattering in a ring geometry plays a crucial role in determining geometric
phases, in contrast to only two time scales, i.e., the adiabatic period and the
dwell time, in an open system. We derive a formula connecting the gauge
invariant geometric phases acquired by time-reversed scattering states and the
circulating (pumping) current. A numerical calculation shows that the effect of
the geometric phases is observable in a nanoscale electronic device.Comment: 9 pages, 3 figure
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