26 research outputs found
Qubit Picture of Virtual Particles
We show that virtual particles, despite being unobservable, can be described
by quantum operators which can be interpreted under certain conditions as valid
qubit quantum states. For a single virtual fermion, we prove that such a state
is a separable mixed 2-qubit state with a well-defined finite temperature. For
spin-1 virtual bosons, we find them to be associated to 4-qubit operators which
can be interpreted as quantum states for some gauges. We also study the
creation of virtual pairs of fermions, where the pair is shown to be associated
to an entangled 4-qubit operator, and show the corresponding quantum circuit.
Finally, we prove that renormalization does not structurally affect these
results. These findings represent new connections between quantum field theory,
quantum information and quantum thermodynamics.Comment: Published version in PRA. The paper was restructured with new
sections added. The spin 1 boson and fermionic pair creation cases were
introduce
Spontaneously broken symmetry restoration of quantum fields in the vicinity of neutral and electrically charged black holes
We consider the restoration of a spontaneously broken symmetry of an
interacting quantum scalar field around neutral, i.e., Schwarzschild, and
electrically charged, i.e., Reissner-Nordstr\"om, black holes in four
dimensions. This is done through a semiclassical self-consistent procedure, by
solving the system of non-linear coupled equations describing the dynamics of
the background field and the vacuum polarization. The black hole at its own
horizon generates an indefinitely high temperature which decreases to the
Hawking temperature at infinity. Due to the high temperature in its vicinity,
there forms a bubble around the black hole in which the scalar field can only
assume a value equal to zero, a minimum of energy. Thus, in this region the
symmetry of the energy and the field is preserved. At the bubble radius, there
is a phase transition in the value of the scalar field due to a spontaneous
symmetry breaking mechanism. Indeed, outside the bubble radius the temperature
is low enough such that the scalar field settles with a nonzero value in a new
energy minimum, indicating a breaking of the symmetry in this outer region.
Conversely, there is symmetry restoration from the outer region to the inner
bubble close to the horizon. Specific properties that emerge from different
black hole electric charges are also noteworthy. It is found that colder black
holes, i.e., more charged ones, have a smaller bubble length of restored
symmetry. In the extremal case the bubble has zero length, i.e., there is no
bubble. Additionally, for colder black holes, it becomes harder to excite the
quantum field modes, so the vacuum polarization has smaller values. In the
extremal case, the black hole temperature is zero and the vacuum polarization
is never excited.Comment: 16 pages, 4 figure
Multipartite Entanglement from Consecutive Scatterings
We study how the successive scattering of spin 1/2 particles with a central
spin 1/2 target particle can generate entanglement between the helicity degrees
of freedom of all scattered particles, effectively producing a multipartite
entangled state. We show that the bipartite entanglement between each pair of
scattered particles, as quantified by the concurrence, is largest for reflected
particles and decreases with the number of scatterings. We study the
entanglement generation as a function of the scattered particles momenta,
angular distribution and mass ratios, and show that there is always a
combination of optimal helicities and momentum which generate the largest
amount of bipartite entanglement.Comment: 4 figure
Entropy of an extremal electrically charged thin shell and the extremal black hole
There is a debate as to what is the value of the the entropy of extremal
black holes. There are approaches that yield zero entropy , while there
are others that yield the Bekenstein-Hawking entropy , in Planck
units. There are still other approaches that give that is proportional to
or even that is a generic well-behaved function of . Here
is the black hole horizon radius and is its horizon area.
Using a spherically symmetric thin matter shell with extremal electric charge,
we find the entropy expression for the extremal thin shell spacetime. When the
shell's radius approaches its own gravitational radius, and thus turns into an
extremal black hole, we encounter that the entropy is , i.e., the
entropy of an extremal black hole is a function of alone. We speculate
that the range of values for an extremal black hole is .Comment: 11 pages, minor changes, added references, matches the published
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