151 research outputs found
Double quantum dots as a high sensitive submillimeter-wave detector
A single electron transistor (SET) consisting of parallel double quantum dots
fabricated in a GaAs/AlGaAs heterostructure crystal is
demonstrated to serve as an extremely high sensitive detector of submillimeter
waves (SMMW). One of the double dots is ionized by SMMW via Kohn-mode plasma
excitation, which affects the SET conductance through the other quantum dot
yielding the photoresponse. Noise equivalent power of the detector for
wavelengths about 0.6 mm is estimated to reach the order of
W/ at 70 mK.Comment: 3 pages, 4 figures, REVTeX, submitted to Appl.Phys.Let
Elastic Mid-Infrared Light Scattering: a Basis for Microscopy of Large-Scale Electrically Active Defects in Semiconducting Materials
A method of the mid-IR-laser microscopy has been proposed for the
investigation of the large-scale electrically and recombination active defects
in semiconductors and non-destructive inspection of semiconductor materials and
structures in the industries of microelectronics and photovoltaics. The basis
for this development was laid with a wide cycle of the investigations on the
low-angle mid-IR-light scattering in semiconductors. The essence of the
technical idea was to apply the dark-field method for spatial filtering of the
scattered light in the scanning mid-IR-laser microscope. This approach enabled
the visualization of large-scale electrically active defects which are the
regions enriched with ionized electrically active centers. The photoexcitation
of excess carriers within a small volume located in the probe mid-IR-laser beam
enabled the visualization of the large-scale recombination-active defects like
those revealed in the optical or electron beam induced current methods. Both
these methods of the scanning mid-IR-laser microscopy are now introduced in
detail in the present paper as well as a summary of techniques used in the
standard method of the lowangle mid-IR-light scattering itself. Besides the
techniques for direct observations, methods for analyses of the defect
composition associated with the mid-IR-laser microscopy are also discussed in
the paper.Comment: 44 pages, 13 figures. A good oldi
Dynamics of coherent and incoherent emission from an artificial atom in a 1D space
We study dynamics of an artificial two-level atom in an open 1D space by
measuring evolution of its coherent and incoherent emission. States of the atom
-- a superconducting flux qubit coupled to a transmission line -- are fully
controlled by resonant excitation microwave pulses. The coherent emission -- a
direct measure of superposition in the atom -- exhibits decaying oscillations
shifted by from oscillations of the incoherent emission, which, in
turn, is proportional to the atomic population. The emission dynamics provides
information about states and properties of the atom. By measuring the coherent
dynamics, we derive two-time correlation function of fluctuations and, using
quantum regression formula, reconstruct the incoherent spectrum of the
resonance fluorescence triplet, which is in a good agreement with the directly
measured one.Comment: 4 pages, 4 figure
Quantum theory of wave mixing on a two-level system
We apply the scattering matrix formalism to wave mixing on a quantum
two-level system. We carry out the fermionization of the two-level system
degrees of freedom using the Popov-Fedotov semions, calculate n-particle
Green's function, and apply the Lehmann-Symanzik-Zimmermannn reduction
procedure. Using the developed approach, we provide a consistent quantum
explanation of the appearance of coherent side peaks observed in an experiment
on the scattering of bichromatic radiation on a two-level artificial atom
\cite{dmitriev2019probing}. We show that the spectrum observed in the
experiment is the result of bosonic stimulated scattering of photons from one
mode of the bichromatic drive to another and vice versa
Ultimate on-chip quantum amplifier
We report amplification of electromagnetic waves by a single artificial atom
in open 1D space. Our three-level artificial atom -- a superconducting quantum
circuit -- coupled to a transmission line presents an analog of a natural atom
in open space. The system is the most fundamental quantum amplifier whose gain
is limited by a spontaneous emission mechanism. The noise performance is
determined by the quantum noise revealed in the spectrum of spontaneous
emission, also characterized in our experiments.Comment: 4 pages, 4 figures + supplemenntary materials accepted for
publication in Phys. Rev. Lett
Coherent superconducting quantum pump
We demonstrate non-adiabatic charge pumping utilizing a sequence of coherent
oscillations between a superconducting island and two reservoirs. Our method,
based on pulsed quantum state manipulations, allows to speedup charge pumping
to a rate which is limited by the coupling between the island and the
reservoirs given by the Josephson energy. Our experimental and theoretical
studies also demonstrate that relaxation can be employed to reset the pump and
avoid accumulation of errors due to non-ideal control pulses.Comment: 4 pages, 3 figure
A phononic crystal coupled to a transmission line via an artificial atom
We study a phononic crystal interacting with an artificial atom { a
superconducting quantum system { in the quantum regime. The phononic crystal is
made of a long lattice of narrow metallic stripes on a quatz surface. The
artificial atom in turn interacts with a transmission line therefore two
degrees of freedom of different nature, acoustic and electromagnetic, are
coupled with a single quantum object. A scattering spectrum of propagating
electromagnetic waves on the artificial atom visualizes acoustic modes of the
phononic crystal. We simulate the system and found quasinormal modes of our
phononic crystal and their properties. The calculations are consistent with the
experimentally found modes, which are fitted to the dispersion branches of the
phononic crystal near the first Brillouin zone edge. Our geometry allows to
realize effects of quantum acoustics on a simple and compact phononic crystal
Asymptotically exact dispersion relations for collective modes in a confined charged Fermi liquid
Using general local conservations laws we derive dispersion relations for
edge modes in a slab of electron liquid confined by a symmetric potential. The
dispersion relations are exact up to , where is a wave
vector and is an effective screening length. For a harmonic external
potential the dispersion relations are expressed in terms of the {\em exact}
static pressure and dynamic shear modulus of a homogeneous liquid with the
density taken at the slab core. We also derive a simple expression for the
frequency shift of the dipole (Kohn) modes in nearly parabolic quantum dots in
a magnetic field.Comment: RevTeX4, 4 pages. Revised version with new results on quantum qots
and wires. Published in Phys.Rev.
Coherent quantum phase slip
A hundred years after discovery of superconductivity, one fundamental
prediction of the theory, the coherent quantum phase slip (CQPS), has not been
observed. CQPS is a phenomenon exactly dual to the Josephson effect: whilst the
latter is a coherent transfer of charges between superconducting contacts, the
former is a coherent transfer of vortices or fluxes across a superconducting
wire. In contrast to previously reported observations of incoherent phase slip,
the CQPS has been only a subject of theoretical study. Its experimental
demonstration is made difficult by quasiparticle dissipation due to gapless
excitations in nanowires or in vortex cores. This difficulty might be overcome
by using certain strongly disordered superconductors in the vicinity of the
superconductor-insulator transition (SIT). Here we report the first direct
observation of the CQPS in a strongly disordered indium-oxide (InOx)
superconducting wire inserted in a loop, which is manifested by the
superposition of the quantum states with different number of fluxes. Similarly
to the Josephson effect, our observation is expected to lead to novel
applications in superconducting electronics and quantum metrology.Comment: 14 pages, 3 figure
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