39 research outputs found
Hybrid continuous dynamical decoupling: a photon-phonon doubly dressed spin
We study the parametric interaction between a single Nitrogen-Vacancy
electronic spin and a diamond mechanical resonator in which the spin is
embedded. Coupling between spin and oscillator is achieved by crystal strain,
which is generated upon actuation of the oscillator and which parametrically
modulates the spins' energy splitting. Under coherent microwave driving of the
spin, this parametric drive leads to a locking of the spin Rabi frequency to
the oscillator mode in the megahertz range. Both the Rabi oscillation decay
time and the inhomogeneous spin dephasing time increase by two orders of
magnitude under this spin-locking condition. We present routes to prolong the
dephasing times even further, potentially to the relaxation time limit. The
remarkable coherence protection that our hybrid spin-oscillator system offers
is reminiscent of recently proposed concatenated continuous dynamical
decoupling schemes and results from our robust, drift-free strain-coupling
mechanism and the narrow linewidth of the high-quality diamond mechanical
oscillator employed. Our findings suggest feasible applications in quantum
information processing and sensing.Comment: 6 pages, 4 figure
Spin-stress and spin-strain coupling in diamond-based hybrid spin oscillator systems
Hybrid quantum systems, which combine quantum-mechanical systems with
macroscopic mechanical oscillators, have attracted increasing interest as they
are well suited as high-performance sensors or transducers in quantum
computers. A promising candidate is based on diamond cantilevers, whose motion
is coupled to embedded Nitrogen-Vacancy (NV) centers through crystal
deformation. Even though this type of coupling has been investigated
intensively in the past, several inconsistencies exist in available literature,
and no complete and consistent theoretical description has been given thus far.
To clarify and resolve these issues, we here develop a complete and consistent
formalism to describe the coupling between the NV spin degree of freedom and
crystal deformation in terms of stress, defined in the crystal coordinate
system XYZ, and strain, defined in the four individual NV reference frames. We
find that the stress-based approach is straightforward, yields compact
expressions for stress-induced level shifts and therefore constitutes the
preferred approach to be used in future advances in the field. In contrast, the
strain-based formalism is much more complicated and requires extra care when
transforming into the employed NV reference frames. Furthermore, we illustrate
how the developed formalism can be employed to extract values for the
spin-stress and spin-strain coupling constants from data published by Teissier
et al..Comment: 14 pages, 3 figures; SOM available for download under
https://quantum-sensing.physik.unibas.ch/publications/research-articles.htm
Resolved sidebands in a strain-coupled hybrid spin-oscillator system
We report on single electronic spins coupled to the motion of mechanical
resonators by a novel mechanism based on crystal strain. Our device consists of
single-crystalline diamond cantilevers with embedded Nitrogen-Vacancy center
spins. Using optically detected electron spin resonance, we determine the
unknown spin-strain coupling constants and demonstrate that our system resides
well within the resolved sideband regime. We realize coupling strengths
exceeding ten MHz under mechanical driving and show that our system has the
potential to reach strong coupling. Our novel hybrid system forms a resource
for future experiments on spin-based cantilever cooling and coherent
spin-oscillator coupling.Comment: 4 pages, 4 figures and supplementary information. Comments welcome.
Further information under http://www.quantum-sensing.physik.unibas.ch
Hybrid spin-nanomechanics with single spins in diamond mechanical oscillators
Hybrid spin-oscillator systems, formed by single spins coupled to mechanical oscillators, have attracted ever-increasing attention over the past few years, triggered largely by the prospect of employing such devices as high-performance nanoscale sensors or transducers in multi-qubit networks. Provided the spin-oscillator coupling is strong and robust, such systems can even serve as test-beds for studying macroscopic objects in the quantum regime.
In this thesis we present a novel hybrid spin-oscillator system that consists of a diamond cantilever whose mechanical motion couples to the spin degree of freedom of embedded NV centers through crystal strain.
This thesis starts with a characterization of the coupling strength between NV spin and resonator motion. Static cantilever bending experiments reveal spin-strain coupling constants of several GHz per unit of strain, corresponding to a single phonon coupling strength \,Hz. Although we demonstrate that our hybrid system resides deep in the resolved sideband regime, our current experimental conditions prevent bringing the diamond resonator to its motional ground state, since spin decoherence rate and mechanical heating rate exceed by several orders of magnitude. However, cooling the resonator, even to its motional ground state, is possible if cantilever dimensions are reduced to the nanometer scale and corresponding experiments are performed at cryogenic temperatures.
While spin-strain coupling is not favorable for such experiments in the quantum regime, it offers many other exciting features. In the second part of this thesis, we report on the implementation of a novel continuous decoupling scheme that protects the NV spin from environmental noise, increasing both Rabi oscillation decay time and inhomogeneous coherence time by two orders of magnitude. The remarkable coherence protection is explained by the robust, drift-free strain-coupling mechanism and the narrow linewidth of the high-quality diamond mechanical oscillators.
A major finding of this thesis is the demonstration of coherent spin manipulation with transverse AC strain fields, which is presented in the third part of this thesis. We show that AC strain driving not only addresses a magnetic dipole forbidden transition, but also allows working in the strong driving regime, in which the induced spin rotation frequency exceeds the initial spin splitting. Few systems have reached this regime, despite the appeal of studying dynamics beyond the rotating wave approximation.
Additionally, continuous strain driving enhances the NV’s spin coherence time by decoupling it from environmental magnetic noise.
In the last part of this thesis, we combine coherent MW and strain spin driving to realize a three-level -system in the NV ground state by coherently addressing all three spin transitions.
Our studies of the spin dynamics not only confirm the theoretical prediction that the global phase (i.e.\,the relative phase of the three driving fields) governs the occurring spin dynamics, but also that closed-contour driving shields the NV's spin from environmental noise without applying complicated decoupling schemes. The corresponding decoupling mechanism is well explained by the effect of noise on the -system Hamiltonian.
Based on our findings, we believe our closed-contour interaction scheme will have future applications in sensing and quantum information processing, for example as a phase sensor or as a test-bed for state transfer protocols
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
Annual reports and accounts
SIGLEAvailable from British Library Document Supply Centre-DSC:1113.253(1996/97) / BLDSC - British Library Document Supply CentreGBUnited Kingdo