30 research outputs found
Observation of Aubry transition in finite atom chains via friction
The highly nonlinear many-body physics of a chain of mutually interacting
atoms in contact with a periodic substrate gives rise to complex static and
dynamical phenomena, such as structural phase transitions and friction. In the
limit of an infinite chain incommensurate with the substrate, Aubry predicted a
structural transition with increasing substrate potential, from the chain's
intrinsic arrangement free to slide on the substrate, to a pinned arrangement
favoring the substrate pattern. To date, the Aubry transition has not been
observed. Here, using a chain of cold ions subject to a periodic optical
potential we qualitatively and quantitatively establish a close relation
between Aubry's sliding-to-pinned transition and superlubricity breaking in
stick-slip friction. Using friction measurements with high spatial resolution
and individual ion detection, we experimentally observe the Aubry transition
and the onset of its hallmark fractal atomic arrangement. Notably, the observed
critical lattice depth for a finite chain agrees well with the Aubry prediction
for an infinite chain. Our results elucidate the connection between competing
ordering patterns and superlubricity in nanocontacts - the elementary building
blocks of friction.Comment: 5 pages, 4 figure
Tuning friction atom-by-atom in an ion-crystal simulator
Friction between ordered, atomically smooth surfaces at the nanoscale
(nanofriction) is often governed by stick-slip processes. To test long-standing
atomistic models of such processes, we implement a synthetic nanofriction
interface between a laser-cooled Coulomb crystal of individually addressable
ions as the moving object, and a periodic light-field potential as the
substrate. We show that stick-slip friction can be tuned from maximal to nearly
frictionless via arrangement of the ions relative to the substrate. By varying
the ion number, we also show that this strong dependence of friction on the
structural mismatch, as predicted by many-particle models, already emerges at
the level of two or three atoms. This model system enables a microscopic and
systematic investigation of friction, potentially even into the quantum
many-body regime.Comment: 10 pages, 5 figure
Multislip Friction with a Single Ion
A trapped ion transported along a periodic potential is studied as a
paradigmatic nanocontact frictional interface. The combination of the periodic
corrugation potential and a harmonic trapping potential creates a
one-dimensional energy landscape with multiple local minima, corresponding to
multistable stick-slip friction. We measure the probabilities of slipping to
the various minima for various corrugations and transport velocities. The
observed probabilities show that the multislip regime can be reached
dynamically at smaller corrugations than would be possible statically, and can
be described by an equilibrium Boltzmann model. While a clear microscopic
signature of multislip behavior is observed for the ion motion, the frictional
force and dissipation are only weakly affected by the transition to multistable
potentials.Comment: 8 pages, 7 figure
Single-atom heat machines enabled by energy quantization
Quantization of energy is a quintessential characteristic of quantum systems.
Here we analyze its effects on the operation of Otto cycle heat machines and
show that energy quantization alone may alter and increase machine performance
in terms of output power, efficiency, and even operation mode. Our results
demonstrate that quantum thermodynamics enable the realization of classically
inconceivable Otto machines, such as those with an incompressible working
fluid. We propose to measure these effects experimentally using a laser-cooled
trapped ion as a microscopic heat machine
Technologies for trapped-ion quantum information systems
Scaling-up from prototype systems to dense arrays of ions on chip, or vast
networks of ions connected by photonic channels, will require developing
entirely new technologies that combine miniaturized ion trapping systems with
devices to capture, transmit and detect light, while refining how ions are
confined and controlled. Building a cohesive ion system from such diverse parts
involves many challenges, including navigating materials incompatibilities and
undesired coupling between elements. Here, we review our recent efforts to
create scalable ion systems incorporating unconventional materials such as
graphene and indium tin oxide, integrating devices like optical fibers and
mirrors, and exploring alternative ion loading and trapping techniques.Comment: 19 pages, 18 figure
Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback
We present a simple method for narrowing the intrinsic Lorentzian linewidth
of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL
Pro) using weak optical feedback from a long external cavity. We achieve a
suppression in frequency noise spectral density of 20 dB measured at
frequencies around 1 MHz, corresponding to the narrowing of the intrinsic
Lorentzian linewidth from 200 kHz to 2 kHz. The system is suitable for
experiments requiring a tunable ultraviolet laser with narrow linewidth and low
high-frequency noise, such as precision spectroscopy, optical clocks, and
quantum information science experiments.Comment: 8 pages, 3 figure
One-dimensional array of ion chains coupled to an optical cavity
We present a novel hybrid system where an optical cavity is integrated with a
microfabricated planar-electrode ion trap. The trap electrodes produce a
tunable periodic potential allowing the trapping of up to 50 separate ion
chains spaced by 160 m along the cavity axis. Each chain can contain up to
20 individually addressable Yb\textsuperscript{+} ions coupled to the cavity
mode. We demonstrate deterministic distribution of ions between the sites of
the electrostatic periodic potential and control of the ion-cavity coupling.
The measured strength of this coupling should allow access to the strong
collective coupling regime with 10 ions. The optical cavity could
serve as a quantum information bus between ions or be used to generate a strong
wavelength-scale periodic optical potential.Comment: 15 pages, 6 figures, submitted to New Journal of Physic
Preventing and Reversing Vacuum-Induced Optical Losses in High-Finesse Tantalum (V) Oxide Mirror Coatings
We study the vacuum-induced degradation of high-finesse optical cavities with
mirror coatings composed of SiO-TaO dielectric stacks, and
present methods to protect these coatings and to recover their initial quality
factor. For separate coatings with reflectivities centered at 370 nm and 422
nm, a vacuum-induced continuous increase in optical loss occurs if the
surface-layer coating is made of TaO, while it does not occur if it
is made of SiO. The incurred optical loss can be reversed by filling the
vacuum chamber with oxygen at atmospheric pressure, and the recovery rate can
be strongly accelerated by continuous laser illumination at 422 nm. Both the
degradation and the recovery processes depend strongly on temperature. We find
that a 1 nm-thick layer of SiO passivating the TaO surface
layer is sufficient to reduce the degradation rate by more than a factor of 10,
strongly supporting surface oxygen depletion as the primary degradation
mechanism.Comment: 14 pages, 7 figure
A many-body singlet prepared by a central spin qubit
Controllable quantum many-body systems are platforms for fundamental
investigations into the nature of entanglement and promise to deliver
computational speed-up for a broad class of algorithms and simulations. In
particular, engineering entanglement within a dense spin ensemble can turn it
into a robust quantum memory or a computational platform. Recent experimental
progress in dense central spin systems motivates the design of algorithms that
use a central-spin qubit as a convenient proxy for the ensemble. Here we
propose a protocol that uses a central spin to initialize two dense spin
ensembles into a pure anti-polarized state and from there creates a many-body
entangled state -- a singlet -- from the combined ensemble. We quantify the
protocol performance for multiple material platforms and show that it can be
implemented even in the presence of realistic levels of decoherence. Our
protocol introduces an algorithmic approach to preparation of a known many-body
state and to entanglement engineering in a dense spin ensemble, which can be
extended towards a broad class of collective quantum states.Comment: 11 pages, 6 figures, and supplementary material
Collective Quantum Memory Activated by a Driven Central Spin
Coupling a qubit coherently to an ensemble is the basis for collective quantum memories. A single driven electron in a quantum dot can deterministically excite low-energy collective modes of a nuclear spin ensemble in the presence of lattice strain. We propose to gate a quantum state transfer between this central electron and these low-energy excitations—spin waves—in the presence of a strong magnetic field, where the nuclear coherence time is long. We develop a microscopic theory capable of calculating the exact time evolution of the strained electron-nuclear system. With this, we evaluate the operation of quantum state storage and show that fidelities up to 90% can be reached with a modest nuclear polarization of only 50%. These findings demonstrate that strain-enabled nuclear spin waves are a highly suitable candidate for quantum memory.We thank E. Chekhovich for helpful discussions. This work was supported by the ERC PHOENICS grant (617985), the EPSRC Quantum Technology Hub NQIT (EP/M013243/1), and the Royal Society (RGF/EA/181068). D. A. G. acknowledges support from St. John’s College Title A Fellowship. E. V. D. and J. M. acknowledge funding from the Danish Council for Independent Research (Grant No. DFF-4181-00416). C. L. G. acknowledges support from a Royal Society Dorothy Hodgkin Fellowship