We
probed
a
gate-tunable
InAs
nanowire
Josephson
weak
link
by
coupling
it
to
microwave
resonator.
Tracking
the
resonator
frequency
shift
when
is
close
pinch-off,
we
observe
that
ground
state
of
latter
alternates
between
singlet
and
doublet
varying
either
gate
voltage
or
superconducting
phase
difference
across
it.
The
corresponding
absorption
spectra
display
lines
approach
zero
energy
singlet-doublet
boundaries,
suggesting
parity
flipping
transitions,
which
are
in
principle
forbidden
spectroscopy
expected
arise
only
tunnel
spectroscopy.
tentatively
interpret
them
means
an
ancillary
isolated
junction
acting
as
reservoir
for
individual
electrons.
Nature Communications,
Journal Year:
2024,
Volume and Issue:
15(1)
Published: Jan. 2, 2024
Abstract
Superconductor/semiconductor
hybrid
devices
have
attracted
increasing
interest
in
the
past
years.
Superconducting
electronics
aims
to
complement
semiconductor
technology,
while
architectures
are
at
forefront
of
new
ideas
such
as
topological
superconductivity
and
protected
qubits.
In
this
work,
we
engineer
induced
two-dimensional
germanium
hole
gas
by
varying
distance
between
quantum
well
aluminum.
We
demonstrate
a
hard
superconducting
gap
realize
an
electrically
flux
tunable
diode
using
interference
device
(SQUID).
This
allows
tune
current
phase
relation
(CPR),
regime
where
single
Cooper
pair
tunneling
is
suppressed,
creating
$$\sin
\left(2\varphi
\right)$$
sin2φ
CPR.
Shapiro
experiments
interpretation
microwave
drive
create
with
≈
100%
efficiency.
The
reported
results
open
up
path
towards
integration
spin
qubit
devices,
resonators
(protected)
qubits
on
same
silicon
technology
compatible
platform.
Minimal
Kitaev
chains
composed
of
two
semiconducting
quantum
dots
coupled
via
a
superconductor
have
emerged
as
promising
platform
to
realize
and
study
Majorana
bound
states
(MBSs),
which
appear
for
fine-tuned
configurations.
We
propose
hybrid
qubit
based
on
Josephson
junction
between
such
double
(DQDs)
embedded
in
superconducting
geometry.
The
makes
use
the
$4\ensuremath{\pi}$-Josephson
effect
create
subspace
even/odd
fermionic
parities
DQD
arrays
hosting
MBSs.
Deep
transmon
regime,
we
demonstrate
that
by
performing
circuit
QED
spectroscopy
Kitaev-transmon
``Kitmon''
qubit,
one
could
observe
distinct
MBS
features
perfect
agreement
with
precise
analytical
predictions
terms
parameters
only.
This
allows
us
extract
polarization
from
microwave
response.
PRX Quantum,
Journal Year:
2025,
Volume and Issue:
6(1)
Published: Jan. 13, 2025
Andreev
(or
superconducting)
spin
qubits
(ASQs)
have
recently
emerged
as
a
promising
qubit
platform
that
combines
superconducting
circuits
with
semiconductor
degrees
of
freedom.
While
recent
experiments
successfully
coupled
two
ASQs,
how
to
realize
scalable
architecture
for
extending
this
coupling
multiple
distant
remains
an
open
question.
In
work,
we
resolve
challenge
by
introducing
achieves
all-to-all
connectivity
between
remote
ASQs.
Our
approach
enables
selective
any
pair
while
keeping
all
other
pairs
uncoupled.
Furthermore,
demonstrate
the
feasibility
efficient
readout
using
circuit
quantum
electrodynamics
techniques
and
compare
different
configurations.
shows
promise
both
gate-based
computing
analog
simulation
applications
offering
higher
than
alternative
solid-state
platforms.
Published
American
Physical
Society
2025
Nature Communications,
Journal Year:
2023,
Volume and Issue:
14(1)
Published: Oct. 25, 2023
Abstract
In
hybrid
Josephson
junctions
with
three
or
more
superconducting
terminals
coupled
to
a
semiconducting
region,
Andreev
bound
states
may
form
unconventional
energy
band
structures,
matter,
which
are
engineered
by
controlling
phase
differences.
Here
we
report
tunnelling
spectroscopy
measurements
of
three-terminal
realised
in
an
InAs/Al
heterostructure.
The
connected
two
loops,
enabling
independent
control
over
differences
and
access
synthetic
structure
the
two-dimensional
space.
Our
results
demonstrate
phase-controlled
molecule,
originating
from
discrete
levels
that
spatially
overlap
hybridise.
Signatures
hybridisation
observed
avoided
crossings
spectrum
anisotropies
space,
all
explained
numerical
model.
Future
extensions
this
work
could
focus
on
addressing
spin-resolved
levels,
ground
state
fermion
parity
transitions
Weyl
bands
multiterminal
geometries.
Physical Review Applied,
Journal Year:
2024,
Volume and Issue:
21(1)
Published: Jan. 25, 2024
Reading
out
the
state
of
a
quantum
system
at
low
temperature
is
generally
challenging,
as
weak
signals
must
be
amplified
while
adding
little
noise
possible.
Also,
some
qubit
types
rely
on
external
magnetic
fields
and
require
magnetic-field-compatible
superconducting
parametric
amplifiers.
Here
an
innovative
amp
design
leverages
nonlinear
response
gate-tunable
kinetic
inductance
proximitized
semiconducting
nanowires.
The
tunability
allows
integration
with
systems,
thanks
to
minimal
crosstalk,
this
can
work
semiconductor-based
spin
qubits
other
hybrid
systems
in
500
mT.
Hybrid
systems
comprising
superconducting
and
semiconducting
materials
are
promising
architectures
for
quantum
computing.
Superconductors
induce
long-range
interactions
between
the
spin
degrees
of
freedom
dots.
These
widely
anisotropic
when
semiconductor
material
has
strong
spin-orbit
interactions.
We
show
that
this
anisotropy
is
tunable
enables
fast
high-fidelity
two-qubit
gates
singlet-triplet
(ST)
qubits.
Our
design
immune
to
leakage
information
into
noncomputational
states
removes
always-on
qubits,
thus
resolving
key
open
challenges
these
architectures.
ST
qubits
do
not
require
additional
technologically
demanding
components
nor
fine-tuning
parameters.
They
operate
at
low
magnetic
fields
a
few
millitesla
fully
compatible
with
superconductors.
By
suppressing
systematic
errors
in
realistic
devices,
we
estimate
infidelities
below
${10}^{\ensuremath{-}3}$,
which
could
pave
way
toward
large-scale
hybrid
superconducting-semiconducting
processors.
Physical Review Research,
Journal Year:
2024,
Volume and Issue:
6(2)
Published: June 17, 2024
Bound
states
in
quantum
dots
coupled
to
superconductors
can
be
a
coherent
superposition
of
with
different
electron
number
but
the
same
fermion
parity.
Electrostatic
gating
tune
this
sweet
spot,
where
dot
has
mean
electric
charge
independent
its
electron-number
Here,
we
propose
encode
information
local
parity
two
tunnel-coupled
embedded
Josephson
junction.
At
qubit
have
zero
dipole
moment.
This
protects
from
dephasing
due
noise
acting
on
potential
each
dot,
as
well
fluctuations
(weak)
interdot
tunneling.
weak
tunneling,
relaxation
is
suppressed
because
disjoint
states.
However,
for
strong
tunneling
system
protected
against
affecting
separately
(energy-level
noise,
dot-superconductor
fluctuations,
and
hyperfine
interactions).
Finally,
describe
initialization
readout
single-qubit
two-qubit
gates
by
pulsing
gate
voltages.
Published
American
Physical
Society
2024
Nature Communications,
Journal Year:
2024,
Volume and Issue:
15(1)
Published: July 30, 2024
Abstract
Gate-tunable
transmons
(gatemons)
employing
semiconductor
Josephson
junctions
have
recently
emerged
as
building
blocks
for
hybrid
quantum
circuits.
In
this
study,
we
present
a
gatemon
fabricated
in
planar
Germanium.
We
induce
superconductivity
two-dimensional
hole
gas
by
evaporating
aluminum
atop
thin
spacer,
which
separates
the
superconductor
from
Ge
well.
The
junction
is
then
integrated
into
an
Xmon
circuit
and
capacitively
coupled
to
transmission
line
resonator.
showcase
qubit
tunability
broad
frequency
range
with
resonator
two-tone
spectroscopy.
Time-domain
characterizations
reveal
energy
relaxation
coherence
times
up
75
ns.
Our
results,
combined
recent
advances
spin
field,
pave
way
towards
novel
protected
qubits
group
IV,
CMOS-compatible
material.
