40 research outputs found
Dynamics and Dissipation induced by Single-Electron Tunneling in Carbon Nanotube Nanoelectromechanical Systems
We demonstrate the effect of single-electron tunneling (SET) through a carbon
nanotube quantum dot on its nanomechanical motion. We find that the frequency
response and the dissipation of the nanoelectromechanical system (NEMS) to SET
strongly depends on the electronic environment of the quantum dot, in
particular on the total dot capacitance and the tunnel coupling to the metal
contacts. Our findings suggest that one could achieve quality factors of
10 or higher by choosing appropriate gate dielectrics and/or by improving
the tunnel coupling to the leads
Adiabatic quantum simulations with driven superconducting qubits
We propose a quantum simulator based on driven superconducting qubits where
the interactions are generated parametrically by a polychromatic magnetic flux
modulation of a tunable bus element. Using a time-dependent Schrieffer-Wolff
transformation, we analytically derive a multi-qubit Hamiltonian which features
independently tunable and -type interactions as well as local bias
fields over a large parameter range. We demonstrate the adiabatic simulation of
the ground state of a hydrogen molecule using two superconducting qubits and
one tunable bus element. The time required to reach chemical accuracy lies in
the few microsecond range and therefore could be implemented on currently
available superconducting circuits. Further applications of this technique may
also be found in the simulation of interacting spin systems.Comment: 11 pages, 6 figure
Time-resolved tomography of a driven adiabatic quantum simulation
A typical goal of a quantum simulation is to find the energy levels and
eigenstates of a given Hamiltonian. This can be realized by adiabatically
varying the system control parameters to steer an initial eigenstate into the
eigenstate of the target Hamiltonian. Such an adiabatic quantum simulation is
demonstrated by directly implementing a controllable and smoothly varying
Hamiltonian in the rotating frame of two superconducting qubits, including
longitudinal and transverse fields and iSWAP-type two-qubit interactions. The
evolution of each eigenstate is tracked using time-resolved state tomography.
The energy gaps between instantaneous eigenstates are chosen such that
depending on the energy transition rate either diabatic or adiabatic passages
are observed in the measured energies and correlators. Errors in the obtained
energy values induced by finite and times of the qubits are
mitigated by extrapolation to short protocol times.Comment: 5 pages, 4 figure
Photonic nano-structures on (111) oriented diamond
We demonstrate the fabrication of single-crystalline diamond nanopillars on a
(111)-oriented chemical vapor deposited diamond substrate. This crystal
orientation offers optimal coupling of nitrogen-vacancy (NV) center emission to
the nanopillar mode and is thus advantageous over previous approaches. We
characterize single native NV centers in these nanopillars and find one of the
highest reported saturated fluorescence count rates in single crystalline
diamond in excess of 10 counts per second. We show that our
nano-fabrication procedure conserves the preferential alignment as well as the
spin coherence of the NVs in our structures. Our results will enable a new
generation of highly sensitive probes for NV magnetometry and pave the way
toward photonic crystals with optimal orientation of the NV center's emission
dipole.Comment: 4 pages original manuscript, 3 pages supplementary materia
Advanced Fabrication of Single-crystal Diamond Membranes for Quantum Technologies
Many promising applications of single crystal diamond and its color centers
as sensor platform and in photonics require free-standing membranes with a
thickness ranging from several micrometers to the few 100 nm range. In this
work, we present an approach to conveniently fabricate such thin membranes with
up to about one millimeter in size. We use commercially available diamond
plates (thickness 50 m) in an inductively coupled reactive ion etching
process which is based on argon, oxygen and SF. We thus avoid using toxic,
corrosive feed gases and add an alternative to previously presented recipes
involving chlorine-based etching steps. Our membranes are smooth (RMS roughness
<1 nm) and show moderate thickness variation (central part: <1 m over
200x200 m). Due to an improved etch mask geometry, our
membranes stay reliably attached to the diamond plate in our chlorine-based as
well as SF-based processes. Our results thus open the route towards higher
reliability in diamond device fabrication and up-scaling.Comment: 9 pages, 4 figures, version 2 accepted for publication in MDPI
micromachine
Advanced Fabrication of Single-Crystal Diamond Membranes for Quantum Technologies
Many promising applications of single crystal diamond and its color centers as sensor platform and in photonics require free-standing membranes with a thickness ranging from several micrometers to the few 100 nm range. In this work, we present an approach to conveniently fabricate such thin membranes with up to about one millimeter in size. We use commercially available diamond plates (thickness 50 μm) in an inductively coupled reactive ion etching process which is based on argon, oxygen and SF6. We thus avoid using toxic, corrosive feed gases and add an alternative to previously presented recipes involving chlorine-based etching steps. Our membranes are smooth (RMS roughness <1 nm) and show moderate thickness variation (central part: <1 μm over ≈200 × 200 μm2). Due to an improved etch mask geometry, our membranes stay reliably attached to the diamond plate in our chlorine-based as well as SF6-based processes. Our results thus open the route towards higher reliability in diamond device fabrication and up-scaling