MC 4060
Candidate
Emma McKay | Applied Math, University of Waterloo
Title
Shape
&
cutoff
in
superconducting
qubits,
work
fluctuations
in
correlation
creation,
&
critical
commentary
Abstract
Part
I
We
apply
the
Unruh-DeWitt
model
for
a
qubit
interacting
with
a
quantum
field
to
a
superconducting
qubit.
We
use
the
flexibility
of
this
model,
as
compared
to
the
spin-boson
model
used
widely
in
the
literature,
to
investigate
the
effect
of
an
ultraviolet
cutoff
in
the
field
and
the
finite
size
of
a
qubit
on
the
dynamics
of
a
qubit.
In
studying
these
features
in
the
setup
of
a
qubit
coupled
to
an
infinite
transmission
line,
we
find
that
both
the
shape
and
scale
of
the
ultraviolet
cutoff
have
a
significant
effect
on
the
qubit’s
dynamics.
For
experimentally
reasonable
parameters,
we
estimate
that
using
an
inaccurate
model
for
the
ultraviolet
cutoff
present
in
the
line
could
introduce
errors
in
calculation
of
probability
of
spontaneous
emission
of
the
qubit
of
around
10%.
This
is
particularly
interesting
in
light
of
the
fact
that
superconducting
lines
have
natural
ultraviolet
cutoffs
due
to
the
breakdown
of
superconductivity
for
high
frequency
electromagnetic
waves.
Part
II
We
investigate
a
unitary
protocol
to
create
correlations
in
a
bipartite
quantum
me-
chanical
system.
The
protocol
was
initially
motivated
by
its
optimal
average
work
cost.
We
calculate
the
fluctuations
in
the
work
cost
and
show
that
for
maximal
generation
of
correlations,
the
fluctuations
in
the
work
cost
are
of
the
order
of
the
average
work
cost,
making
the
protocol
energetically
rather
unreliable.
We
additionally
explore
some
of
the
nuances
of
the
discussion
around
work
in
quantum
systems
with
discussion
of
the
current
literature
as
well
as
some
philosophical
motivations
of
the
most
widely
used
definitions
of
work.
Throughout
the
thesis,
we
comment
on
the
motivations
for
this
research
and
its
effect
on
our
world.
In
doing
so,
we
find
multiple
ways
that
supporting
the
project
of
developing
quantum
technology
supports
injustice.
We
also
model
a
methodology
for
engaging
with
societal
and
ethical
implications
of
work
in
theoretical
physics.