Acta Materialia,
Journal Year:
2024,
Volume and Issue:
276, P. 120153 - 120153
Published: July 4, 2024
Superconducting
quantum
circuits
(SQC)
are
one
of
the
most
promising
hardware
platforms
for
computing,
yet
their
performance
is
currently
limited
by
presence
various
structural
defects
inside
circuit's
structure.
Despite
impressive
progress
in
past
decade,
a
precise
understanding
origin
these
from
fabrication
processes
and
impact
on
coherence
still
lacking.
In
this
study,
we
performed
comprehensive
investigation
microstructure,
superconductivity,
resonator
quality
factor
Nb
films
deposited
high-power
impulse
magnetron
sputtering
(HiPIMS)
direct
current
(DC)
sputtering.
A
suite
characterization
techniques,
including
electron
microscopy
with
spectroscopy,
secondary
ion
mass
spectrometry,
magneto-optical
microscopy,
pump-probe
reflectivity
spectroscopy
used.
We
reveal
that
niobium
(Nb)
resonators
fabricated
using
HiPIMS
exhibit
smaller
average
grain
size,
thicker
surface
oxide
larger
thickness
variations
(rougher
surface),
amorphous
Nb/Si
interface
layer
compared
to
samples
DC
identified
oxides
(mainly
located
at
along
boundaries)
Nb-Si
layers
(at
interface)
major
potential
sources
two-level
system
(TLS),
while
off-stochiometric
suboxides
close
surface,
crystalline
(i.e.,
dislocations
boundary,
point
introduced
during
deposition)
main
contributors
non-TLS
sources.
Our
findings
clarify
relationship
between
different
loss
mechanisms,
highlighting
importance
material
microstructure
control
optimization
SQC.
Applied Physics Letters,
Journal Year:
2024,
Volume and Issue:
124(13)
Published: March 25, 2024
Superconducting
qubits
have
arisen
as
a
leading
technology
platform
for
quantum
computing,
which
is
on
the
verge
of
revolutionizing
world's
calculation
capacities.
Nonetheless,
fabrication
computationally
reliable
qubit
circuits
requires
increasing
coherence
lifetimes,
are
predominantly
limited
by
dissipations
two-level
system
defects
present
in
thin
superconducting
film
and
adjacent
dielectric
regions.
In
this
paper,
we
demonstrate
reduction
losses
three-dimensional
radio
frequency
niobium
resonators
atomic
layer
deposition
10
nm
aluminum
oxide
Al2O3
films,
followed
high
vacuum
heat
treatment
at
650
°C
few
hours.
By
probing
effect
several
treatments
Al2O3-coated
samples
x-ray
photoelectron
spectroscopy
plus
scanning
conventional
resolution
transmission
electron
microscopy
coupled
with
energy
loss
dispersive
spectroscopy,
witness
dissolution
native
oxides
modification
Al2O3-Nb
interface,
correlates
enhancement
quality
factor
low
fields
two
1.3
GHz
cavities
coated
Al2O3.
Physical Review Research,
Journal Year:
2024,
Volume and Issue:
6(1)
Published: March 27, 2024
The
control
of
material
loss
mechanisms
is
playing
an
increasingly
important
role
for
improving
coherence
times
superconducting
quantum
devices.
Such
losses
can
be
characterized
through
the
measurement
planar
resonators,
which
reflect
resonance's
quality
factor
${Q}_{l}$.
resonance
consists
both
internal
(material)
as
well
coupling
when
photons
escape
back
into
circuit.
combined
are
then
described
${Q}_{l}^{\ensuremath{-}1}=\mathrm{Re}{{Q}_{c}^{\ensuremath{-}1}}+{Q}_{i}^{\ensuremath{-}1}$,
where
${Q}_{c}$
and
${Q}_{i}$
factors
resonator,
respectively.
To
separate
relative
contributions
to
${Q}_{l}$,
diameter-correcting
circle
fits
use
algebraic
or
geometric
means
fit
signal
on
complex
plane.
However,
such
produce
varied
results,
so
address
this
issue,
we
a
combination
simulation
experiment
determine
reliability
fitting
algorithm
across
wide
range
values
from
${Q}_{i}\ensuremath{\ll}{Q}_{c}$
${Q}_{c}\ensuremath{\ll}{Q}_{i}$.
In
addition,
develop
protocol
that
not
only
reduce
errors
by
$\ensuremath{\gtrsim}2$
but
also
mitigates
influence
background
results.
This
technique
generalized
other
systems
beyond
resonators.
Materials for Quantum Technology,
Journal Year:
2024,
Volume and Issue:
4(2), P. 025801 - 025801
Published: May 14, 2024
Abstract
The
performance
of
state-of-the-art
superconducting
quantum
devices
is
currently
limited
by
microwave
dielectric
loss
at
different
interfaces.
α
-tantalum
a
superconductor
that
has
proven
effective
in
reducing
and
improving
device
due
to
its
thin
low-loss
oxide.
Here,
we
demonstrate
the
fabrication
high-quality
factor
coplanar-waveguide
resonators
directly
on
pristine
300
mm
silicon
wafers
over
variety
metal
deposition
conditions
perform
comprehensive
material
electrical
characterization
study.
Additionally,
apply
surface
treatment
based
hydrofluoric
acid
allows
us
modify
surfaces,
leading
reduction
two-level
system
three.
This
can
be
entirely
attributed
removal
oxides.
Our
study
indicates
large
scale
manufacturing
circuits
should
indeed
feasible
suggests
viable
avenue
materials-driven
advancements
circuit
performance.
Physical Review X,
Journal Year:
2024,
Volume and Issue:
14(4)
Published: Nov. 20, 2024
The
Kerr-cat
qubit
is
a
bosonic
in
which
multiphoton
Schrödinger
cat
states
are
stabilized
by
applying
two-photon
drive
to
an
oscillator
with
Kerr
nonlinearity.
suppressed
bit-flip
rate
increasing
size
makes
this
promising
candidate
implement
quantum
error
correction
codes
tailored
for
noise-biased
qubits.
However,
achieving
strong
light-matter
interactions
necessary
stabilizing
and
controlling
has
traditionally
required
microwave
drives
that
heat
the
degrade
its
performance.
In
contrast,
coupling
port
removes
need
at
expense
of
large
Purcell
decay.
By
integrating
effective
band-block
filter
on
chip,
we
overcome
trade-off
realize
scalable
2D
superconducting
circuit
high
coherence.
This
provides
30
dB
isolation
frequency
negligible
attenuation
frequencies
stabilization
readout.
We
experimentally
demonstrate
nondemolition
readout
fidelity
99.6%
eight
photons.
Also,
have
high-fidelity
universal
control
over
qubit,
combine
fast
Rabi
oscillations
new
demonstration
X(π/2)
gate
through
phase
modulation
drive.
Finally,
lifetime
architecture
examined
as
function
up
ten
photons
oscillator,
time
higher
than
1
ms
only
linear
increase
phase-flip
rate,
good
agreement
theoretical
analysis
circuit.
Our
shows
promise
building
block
fault-tolerant
processors
small
footprint.
Published
American
Physical
Society
2024
Applied Physics Letters,
Journal Year:
2025,
Volume and Issue:
126(2)
Published: Jan. 13, 2025
Superconducting
flip-chip
interconnects
are
crucial
for
the
three-dimensional
integration
of
superconducting
circuits
in
sensing
and
quantum
technology
applications.
We
demonstrate
a
simplified
approach
device
using
commercially
available
indium
microspheres
an
in-house-built
transfer
stage
bonding
two
chips
patterned
with
thin
films.
use
gold-passivated
niobium
or
nitride
layer
as
under-bump
metallization
(UBM)
between
aluminum-based
wiring
interconnect.
At
millikelvin
temperatures,
our
assembly
can
transport
supercurrent
tens
milliamperes,
limited
by
smallest
geometric
feature
size
critical
current
density
UBM
not
show
that
pressed
interconnect
itself
carry
exceeding
1
A
due
to
its
large
about
500
μm
diameter.
Our
does
require
neither
electroplating
nor
patterning
indium.
The
process
need
bonder
be
realized
top
chip
transparency
through-vias
alignment.
These
devices
utilized
applications
few
carrying
currents
at
temperatures.
We
use
density
functional
methods
to
identify
the
atomic
configurations
of
H
and
D
atoms
trapped
by
O
impurities
embedded
in
bulk
Nb.
The
are
located
at
octahedral
position
Nb
body-centered
cubic
(BCC)
lattice,
(D)
tunnel
between
two
degenerate
tetrahedral
sites
separated
a
mirror
plane.
Using
nudged
elastic
band
(NEB)
methods,
we
calculate
double-well
potential
for
O-H
O-D
wave
functions
splittings
atoms.
Our
results
agree
with
those
obtained
from
analysis
heat
capacity
neutron
scattering
measurements
on
low
concentrations
O-D.
Published
American
Physical
Society
2025
Nano Letters,
Journal Year:
2025,
Volume and Issue:
unknown
Published: Jan. 27, 2025
The
advent
of
two-dimensional
van
der
Waals
materials
is
a
frontier
condensed
matter
physics
and
quantum
devices.
However,
characterizing
such
remains
challenging
due
to
the
limitations
bulk
material
techniques,
necessitating
development
specialized
methods.
Here,
we
investigate
superconducting
properties
Bi2Sr2CaCu2O8+x
flakes
by
integrating
them
with
hybrid
microwave
resonator.
resonator
significantly
modified
interaction
flake
while
maintaining
high
quality
factor
(3
×
104).
We
also
observe
significant
upshift
frequency
increasing
temperature,
as
well
positive
nonlinearity.
These
effects
originate
from
presently
unknown
microscopic
mechanism
within
flake,
can
be
modeled
two-level
system
bath
interacting
resonant
mode.
Our
findings
open
path
for
circuits
exploring
novel
developing
new
devices
technology.
Applied Physics Letters,
Journal Year:
2025,
Volume and Issue:
126(4)
Published: Jan. 27, 2025
Superinductors
have
become
a
crucial
component
in
the
superconducting
circuit
toolbox,
playing
key
role
development
of
more
robust
qubits.
Enhancing
performance
these
devices
can
be
achieved
by
suspending
superinductors
from
substrate,
thereby
reducing
stray
capacitance.
Here,
we
present
fabrication
framework
for
constructing
circuits
with
suspended
planar
architectures.
To
validate
effectiveness
this
process,
systematically
characterize
both
resonators
and
qubits
arrays
Josephson
junctions,
ultimately
confirming
high
quality
superinductive
elements.
In
addition,
process
is
broadly
compatible
other
types
designs.
Our
results
not
only
pave
way
scalable
architectures
utilizing
but
also
provide
primitive
future
investigation
loss
mechanisms
associated
device
substrate.