MC 5136

## Speaker

Robert Jonsson, Department of Applied Mathematics, University of Waterloo

## Title

Relativistic Quantum Communications

## Abstract

Since
their
discovery,
General
Relativity
and
Quantum
Theory
revolutionized
not
only
our
view
of
the
world
but
by
means
of
the
digital
revolution,
in
fact,
our
everyday
life
as
well.
However
the
problem
of
unifying
these
two
successful
theories
remains
unsolved
for
over
half
a
century
by
now.

In
recent
years
an
approach
called
Relativistic
Quantum
Information
has
produced
many
interesting
results
by
connecting
quantum
and
relativistic
effects
through
Information
Theory.
Following
this
idea,
we
study
the
communication
between
simple
quantum
systems
that
are
connected
via
quantum
fields,
so
called
Unruh-DeWitt
detectors,
in
relativistic
settings.
This
model
may
serve
as
a
general
toy
model,
e.g.,
for
signalling
between
atoms
via
the
exchange
of
photons
in
curved
spacetimes.

In
this
talk,
we
discuss
the
general
structure
of
the
quantum
channel
between
two
Unruh-DeWitt
detectors.
We
show
why
Alice
should
not
try
to
encode
messages
to
Bob
using
energy
eigenstates
of
her
detector,
but
why
she
should
use
superposition
states
instead. Furthermore,
we
discuss
recent
work,
where
the
quantum
channel
was
applied
to
quantum
field
in
cavities.
Using
causality
arguments
the
fidelity
of
approximative
methods,
that
only
use
a
finite
number
of
modes,
was
investigated
in
relativistic
scenarios.